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SE-R Performance Drivetrain Tips

Written by Mike Kojima

Last updated: 12/24/98


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Once you start to modify your SE-R, you may inadvertently run up against the limitations of the stock drivetrain. Although the basic major parts of the SE-R’s drivetrain are bulletproof their are some weak links that can benefit from some modifications. Before you get started please read and understand this disclaimer. We must absolve ourselves of the old "failure to warn" clause.

Warning! High performance driving can result in property damage and injury. Modifying cars for use in ways other than the manufacturer intended can be dangerous. Failure of clutch and drivetrain components can be very damaging to people or property. The tips contained below can potentially result in property damage or injury. If this advice is followed, it is at the readers PERSONAL discretion, with the reader assuming all risk. The editors and staff of se-r.net are not responsible for anything that might happen to the reader. If the reader cannot deal with this he should sell his car and drive something like a Buick and NEVER, EVER ATTEMPT TO MODIFY IT. If you are a lame ass, sue-happy, Larry Parker calling, wiener please do not read any further and never come back to se-r.net again.

Is the above clear to you? If it is, lets get down to business!

Clutches

Perhaps the weakest link in the SE-R’s drivetrain is the clutch. Although the stock clutch usually holds up fine on a stock motor or even a built motor up to about 150 wheel hp, abusive drag race starts or slam shifting usually makes quick work of it. Turbo or Nitrous SE-R’s will eat a stock clutch instantly. A carefully driven 50 shot will work for a while on a stock clutch, but it will be on the edge and must be driven carefully.

A clutches durability depends a lot on the driver. My car has a Clutchmasters stage 3 clutch which holds up just fine on my 190 hp + 100 hp nitrous unit car which perhaps is one of the most powerful SE-R’s currently out. A friend of mine has exploded 3 of these same clutches. He always tells me that the clutches are crappy and he just drives them like "normal". Well, I let him drive my car one day and was horrified when he immediately started doing full throttle, no let off speed shifts up and down the street in my car! When I asked him what the hell did he think he was doing to my car he seemed surprised and said, "what, I always drive like this". Needless to say, he doesn’t drive my car anymore. I drive pretty normal and do not abuse my drivetrain unless there is a good reason to like when I am racing. His normal and my normal are two very different normals!

This all goes to say that clutch life is very dependent on your driving style. Many people think that just because they have a heavy duty clutch, they can beat the crap out of it no problem. While a HD clutch can withstand this abuse better than a stock clutch, they are by no means bulletproof to all abuse. Anything can break on a car if you try!

If you get a clutch strong enough to withstand your driving style or engine power, other weak links of your drive train will be exposed. Modified SE-R’s can suffer from ripped motor mounts, cracked transmission cases, etc. and a heavy duty clutch will do more to bring these negative attributes out as a slipping clutch can cushion the rest of the drive train.

The main suppliers of SR20 clutches to my knowlege are: JWT, Stillen, Clutchmasters, Centerforce, Dynamic Autosports, Redline Racing and Clutch Specialties.

A clutch consists of two parts, the pressure plate and the disc. The disc contains the friction material and is coupled to the input shaft of the transmission. The pressure plate contains the diaphragm spring, the pressure ring and the housing. The pressure plate bolts to the flywheel which bolts to the engine. The clutch is the device that couples the engine to the transmission, being a variable slippage coupling that is driver controlled, thus allowing the car to get moving smoothly with a little coordination on the drivers part.

The pressure plate design that just about all imports use , including the SE-R is called a diaphragm type. Domestic car can sometime use other pressure plate designs such as the Borg and Beck or the Long type designs. Diaphragm clutches use a circular, cone-shaped spring called a diaphragm spring to apply clamp loads to the clutch disk. The main advantage of the diaphragm pressure plate is that it has a light pedal for the amount of clamping load delivered with a smooth linear engagement.

The diaphragm spring is the thing that the throwout bearing and arm pushes on to disengage the clutch. It is visible in the center hole of the pressure plate and is the thing with the multiple "fingers" that the T/O bearing rests against. The diaphragm spring is the thing that provides the pressure that clamps the disk to the flywheel. Your typical HD clutch has a thicker diaphragm spring to increase the clamping force on the disc. Clamping force is perhaps the most important attribute to making a clutch hold high horsepower. The more clamping force, the harder the pressure ring smashes the disc to the flywheel and the less likely anything will slip. Some extreme clutches even have a double diaphragm spring which is usually two stock springs stacked on top of each other. The Dynamic Autosports Double D and the Redline clutch are like this I believe. These clutches have so much clamping force (approximately 100% more) that they can cause excessive wear on your crankshaft thrust bearings, even to the point where they fall out! Not good. For limited use such as for a very high horsepower (400+ hp nos or turbo), slicked-up, drag only car where maximum hold is critical it would probably be a good choice, maybe your only choice. They typically have a very high pedal effort which is hard on your leg in bumper to bumper traffic!

The pressure ring is the cast iron piece that the clutch disc rubs against. The pressure ring is smashed against the clutch disc by the diaphragm spring. When you push the clutch pedal you push the throwout bearing into the inside of the diaphragm spring. The spring bends over the fulcrum/ pivot stamped into the clutch cover and releases pressure on the pressure ring allowing the clutch to disengage. Some HD clutches have a beefier, thicker pressure rings to resist warping with heavier clamp loads and high heat. No SE-R HD clutches have this feature yet to my knowledge but if you spot it you’ll know what it’s there for.

The clutch housing is obviously the housing that contains everything. The fulcrum that the diaphragm springs pivots on is stamped into the clutch housing. Some HD clutches have a heavier housing stamped of thicker gauge steel to hold up to increased clamping pressures of thicker diaphragm springs without flexing. This gives more consistent clutch action and improved clamping.

Most available SE-R HD clutches are stock pressure plates modified with heavier diaphragm springs cut down to fit from another type of clutch, or two stock diaphragm springs stacked on top of each other. Basically this is an ok way to get more clamping pressure. Clutch Specialties, Center Force and I believe the Dynamic DD and Redline units are constructed like this. Clutch masters uses an AP Racing pressure plate re-drilled for the SE-R flywheel bolt pattern. This pressure plate has a greater motion ratio of the diaphragm spring. That means the fulcrum that the diaphragm spring bends against is moved toward the outside of the springs circumference. This gives the throwout arm more leverage when it disengages the spring by bending it over the fulcrum. That’s why the Clutch Masters pressure plate can have such a light pedal effort for the 40% higher clamping effort it offers. Stillen and JWT use a Pressure plate very similar to Clutchmasters.

Some pressure plates have a ring of weights on a cable attached to the fingers of the diaphragm spring. These weights are supposed to offer a centrifugal assist, increasing clamping pressure at high RPM. Centerforce clutches are known for this. Personally I think this does very little good and causes overcentering. Overcentering is when the diaphragm springs fingers get pushed past the normal centerline of the diaphragm spring. When this occurs, centrifugal force keeps the fingers of the spring disengaged causing the clutch pedal to stick to the floor during high RPM shifts, like when speed shifting. This is a great way to blow up your motor. The centrifugal weights on the Centerforce makes it even more prone to overcentering. Try this, if you know someone who has a Centerforce clutch, push the pedal down about of the way down and rev the motor up. You can feel the pedal get lighter with increasing revs. That is the clutch wanting to overcenter. All diaphragm type clutches are prone to overcenter to some degree so you want to be sure that you are not pulling too much cable in your clutch adjustment.

The clutch disk is a even more complicated piece with lots of variation. The stock disk is designed for long life on a stock engine under normal driving conditions with smooth operating characteristics. To withstand abuse a HD disk is going to have some compromises built into it that will make it less smooth, worse for street driving.

First off the stock disk’s friction material is designed for smooth operation. It is made of fiberglass and metal fiber reinforced cellulose in a thermosetting phenolic resin base. This material is sort of like an organic brake pad. The metal and fiberglass strands provide burst strength (which is the friction materials resistance to breaking up falling apart) and high temp frictional properties. The cellulose is like cardboard (no kidding) and helps initial grip. Let’s say that this stuff does not hold up to abuse so well but offers smooth engagement. In the bad old days, asbestos was used in place of the cellulose. Asbestos was superior as a friction material due to it’s high heat resistance. Unfortunately it is a powerful carcinogen and is now a no no. Once asbestos was banned it became very difficult for manufactures to make a smooth engaging, long lasting, HD disk. The stock Nissan disk is not to bad if not glazed by abuse, when combined with a heavy duty pressure plate. This combo can contain up to 270 hp with the right pressure plate. The HD pressure plate with the stock disc will be smooth and chatter free. The stock friction material is forgiving. If you start to smoke the clutch and you back off, it can recover enough to still be useable most of the time. This is the best combo for most list members limited to bolt on mods in my opinion.

HD disks have friction material made of several different things. A mild HD disk usually uses Kevlar strands in a phenolic resin base. Kevlar is a space age aramid (in the nylon family) fiber that is six times stronger than steel in tension and is very heat resistant. Kevlar is the same stuff that bullet proof vests are made of. Kevlar offers superior burst strength and wearing characteristics but has relatively poor frictional gripping properties. This makes for smooth engagement characteristics but so so holding power. Because of this kevlar disks need lots of clamp pressure to hold without slipping. Although these discs are called carbon/kevlar by the catalog marketing hacks, they do not contain any carbon fiber. I am not sure why they are called carbon kevlar! It must be because aramid fibers are carbon based? It sure sounds hi-tech. A kevlar disk must be carefully broken in for 500 miles of gentile bumper to bumper traffic before it can be abused. The flywheel on a kevlar disk must be meticulously resurfaced and no oil or grease can contaminate the disk, not even fingerprints. If all of this is done correctly a Kevlar disk can provide a very long service life because of its inherit toughness. Kevlar is also prone to glazing from abuse. Once a kevlar disk is glazed, it will most likely not recover and must be replaced. A kevlar disk must be babied through it’s break-in period and is sensitive to many factors. Finally kevlar is low abrasive, easy on the flywheel and pressure ring surfaces causing little wear of these parts, another plus if long life is important to you.

For extreme applications there are metal discs. These use a sintered copper friction material that can contain particles of carbon or ceramics. Copper is an excellent conductor of heat and has self lubricating properties, that’s why its favored as a base friction material. The carbon and ceramics help give the copper bite. Kind of like the grit in Lava soap or hand cleaner. This sort of friction material is called carbon-ceramic or carbon-metallic or even just metal by the marketing hacks. The metallic discs are the ultimate in grip. They work better when hot and last the longest of any of the friction materials. Being very hard, they do not have a very smooth engagement, like an on off switch, and thus are poor for street use. They also wear the friction face of the flywheel and the pressure ring badly. When you replace one of these clutches, you have to replace everything! At the minimum your flywheel will need a heavy re-surfacing.

Clutch discs have a few different features that control their operating properties. Most stock and HD clutches have what is called a marcel spring. This is a wavy corrugated washer looking stuff that is bonded to the disc right below the friction material. You can see it when looking at a clutch disc on its edge. The marcel acts like a cushion, smoothing out the final engagement of the friction material by allowing the clamping forces to build up a little slower. When the clutch is fully engaged, the marcel smashes flat and has no effect. The marcel is removed from racing type and metallic clutches for two reasons. The marcel prevents the friction material from being 100% bonded to the disc, reducing burst strength somewhat and it also increases engagement travel, possibly slowing shifts which is a little harder on the syncros.

The hub of the disk has some features that affect engagement characteristics also. Stock and HD clutches have sprung hubs. These are two pieces floating hubs that have the friction material attached to one side and the transmission input shaft splines on the other. Captured coil springs or rubber bumpers are retained between the two hub sections to allow some rotational cushion when the clutch is let out. Sprung hubs really help make a clutch streetable, meaning reducing chatter and jerk when letting the clutch out, to a large degree.

I recommend staying away from discs with rubber bumpers as they tend to get chewed up and fall out under hard use. Some discs also have the coil springs fall out rather easily also. If your clutch pedal suddenly gets stuff and the clutch refuses to disengage completely, one of your hub springs has probably fallen out and has gotten jammed between the pressure ring and one side of your disc. This is pretty common failure on the early Clutchmasters kevlar discs. Newer Clutchmasters discs are substantially beefed up in this area.

Extreme racing disks usually have no hub springs. This is to get the crispest shifting action as the engagement and disengagement of the clutch is very crisp and defined. This takes load off of the syncros and can make for very fast shifting. Without the complexities of the hub springing, the hub can be lighter and stronger also. Solid hub disks are very difficult to drive on the street and exhibit extreme on-off engagement characteristics. They chatter and are impossible to drive smoothly. Solid hub discs can also contribute to the failure of other drivetrain components like the tranny, halfshafts or C/V joints as they transmit 100% of the shock to these parts. Usually road racing or circle track applications are solid disk as crisp shifting and minimal weight are important for these applications. Solid disk clutches must be popped and wheels spun to get them going. Trying to slip them for a smooth street start will burn them out fast. No matter how carefully you slip them they will still chatter as they engage.

For really hard use, a full metal disc is needed, usually of the puck variety. These discs have anywhere from 8-3 pucks of friction material on metal arms extending from the center hub. The fewer the amount of pucks the higher per-unit load is placed on the friction material, increasing the clamping force. Thus a full race disc may only have three pucks with a solid hub while and extreme use street/strip disc may have 8 or more pucks with a sprung hub.

The three puck disc will almost be unstreetable while the 8 puck will have a little judder but be driveable by a tolerant person. A three puck with a solid hub must be popped to get the car moving as slipping it will burn it out. Remember that if you are pumping lots of power through you clutch you have to put up with some compromises to contain that power. Your stock clutch was not designed to handle huge power increases that turbos or nos can put through it.

A 8-puck metal disc can handle 400+ hp with the right pressure plate and a three puck can hold even more. For drag racing with big slicks with a turbo or nos these types of disks are about the only choice.

As a compromise for street/strip or weekend warrior cars there are dual compound type clutches available. The Centerforce dual friction or the Clutchmasters stage III are examples of this type of clutch. These typically have an 8 or more puck metallic friction material on one side of the disc with a marcel and kevlar material on the other with a sprung center hub.

The kevlar side of the disc provides a smooth initial engagement while the puck side provides bite. These discs can contain up to 300 hp. There have been reports of the Clutchmasters version of this disk failing due to hub breakage but Clutchmasters has recently gone to a stronger hub section. I have put as much as 250 hp through my Clutchmasters stage III disc without any problems and I am very pleased with it’s very smooth engagement and near stock driveabilty in bumper-to -bumper traffic.

Here are some of my reviews of some popular clutches:

Stock Genuine Nissan
Really a pretty good clutch. If you have less than 50 more hp than stock, it should hold up pretty well unless you are a thrash. The smoothest and easiest on the drivetrain of any clutch. Beware of imitation stock clutches made in taiwan. These are very prone to have the hub spring fall out. The stock clutch is good for people with just the bolt on power adders. If you have a turbo or nos forget it.

Centerforce
Based on a resprung stock pressure plate. This clutch is prone to overcenter and has burst on many people I know. It is a little better than stock. Centerforce has a good reputation with domestic (USA) cars but there import stuff is so so. I recommend this as a stock replacement only. The dual friction disc which has some semi-metallic pucks on one side and kevlar on the other may be better, but I don’t know anyone who has tried this combo. Due to the overcentering problem one must be careful to adjust the clutch cable to minimize the pull. One must be careful while speedshifting as overcentering can cause overreving if the clutch sticks to the floor.

Clutchmasters
A very popular clutch on the list but somewhat problematic. The pressure plate has about 40% more clamping force than stock but still has a very light pedal effort. Clutchmasters does this by changing the motion ratio on the diaphragm spring so the clutch pedal can get more leverage. The only drawback to this is that the Clutchmasters clutch has a longer engagement travel which can make speed shifting a little more difficult. Speed shifting is not a very good practice anyway so this may be a small point. Most users will never notice the extra pedal travel. The longer pedal travel makes the clutch a little more sensitive to cable adjustment. If the cable is too tight the clutch will be left partially disengaged were it will slip and glaze over in no time. Several list members have done this to my knowledge.

The Clutchmasters clutches diaphragm spring is also lower in height than the stock diaphragm spring. This means that some slack might need to be taken out of the clutch cable for the clutch to fully disengage. If your clutch cable is old and stretched, you may need a new one. Also you may need to get rid of one of the clutch cable freeplay adjuster lock nuts to get more cable pull. If you don’t do this the clutch will engage near the floor and maybe not fully disengage. Grinding shifts will result.

The Clutchmasters clutch can overcenter if the cable is to tight also but it is not as sensitive to this as the Centerforce clutch.

Overall, the pressure plate design is very good but the discs have been know to fail both by bursting (two incidents that I am aware of) and more commonly, having the hub springs fall out. Clutch masters has recently redesigned their hub to be much stronger which should make their clutch a very, very good setup. Clutchmasters can also do a variety of stages of clutch. Clutchmasters can also do custom applications for very high horsepower cars.

Stage 1- CM pressure plate and stock disc- This works very well with no listmember complaints that I can recall so far. Can hold 250 or so hp. Very smooth and pleasant to use for daily driving.

Stage 2- CM pressure plate with CM kevlar disk. The stage II disk features a kevlar lining with both a marcel spring and a sprung hub. This has been a problematic application for list members. Early versions were very sensitive to break-in and had busting problems. Hub spring fall out was also a problem. The latest CM disks have a segmented kevlar friction material and much stronger hubs. The segmented kevlar lining increases the per-unit clamp load over the old style full face kevlar lining. These should be fine but it seems like the list is running scared! For good reasons! This disc, like all kevlar and metal discs needs to be carefully broken in for 500 miles. Cleanliness is next to godliness during installation also, as any oil reside, even fingerprints can cause problems. Trouble will happen to those who ignore this. Once the installation and break-in hassles are overcome, the stage two clutch is very smooth, long lasting and streetable.

Stage 3- CM pressure plate with CM kevlar/metal dual compound disk. This disk has a marcel sprung, segmented kevlar lining on one side and an 8-puck metal lining on the other. The center hub is sprung. I have this in my car and love it. My car puts out about 250 hp on nos and this disk should be able to support close to 300 hp. There has been one failure of this disk to my knowledge. This disk will chatter if you try and make it do so but is amazingly streetable otherwise. This is probably the best all around disk for medium hp cars. This disk must be broken in for 500 miles. The neat thing is that the metal pucks are on the pressure plate side while the kevlar is on the flywheels side. That way the abrasive metal pucks only tear up the pressure ring which gets replaced during a clutch change anyway.

Stage 4- CM pressure plate with 8-puck disc and sprung hub. Pretty radical. Hub is real strong. This pup should never break. This is the strongest clutch that is streetable. Has some chatter and jerk but is manageable with a coordinated foot. Not recommended unless you have a turbo or a big nos shot.

Stage 5- Ditto but in 3 puck. This is a very hard hitting clutch for all out drag or road racing with slicks, etc. Not streetable unless you like a chattering jerky feel.

Beyond- solid hub and dual disc custom stuff for mega $$$ and no streetablity. Call for application.

CM has been pretty good for warrantying bad clutches as long as you speak to Chris Jewal, the owner of Clutchmasters. I think with the recent redesigns most of CM’s problems should be behind them.

Jim Wolf Technology
The JWT clutch is perhaps one of the most successful clutches used by listmembers. I have not heard of any failures of one. JWT uses a stock disk for applications up to 250 or so hp and a sprung full metal disk for special high horsepower applications. The JWT clutch is smooth and reliable and perhaps the favorite of the list. I have driven these and they feel very much like the Clutchmasters clutch with a light pedal and smooth engagement. The JWT clutch, like all their products, works as delivered. If I had no experience with Clutchmasters, the JWT unit would be my first choice.

JWT also offers other types of metal disks for higher horsepower applications. I have not tried any of these but if it is like typical JWT stuff, it should work well.

Stillen
The Stillen clutch has been somewhat problematic much like the early Clutchmasters clutches but I believe that they have solved all of the early problems and now work well. I do not have any personnel experience with them and am unsure of the construction details but I believe they presently work very well for applications of up to 250 hp.

Clutch Specialties
This is a stock Nissan pressure plate rebuilt with a heavier diaphragm spring. The pressure plate is much like the Centerforce unit but with a much heavier diaphragm spring instead of the problematic centrifugal weight ring. Clutch Specialties uses the same motion ratio as a stock diaphragm so the pedal effort ends up being about 25% higher than stock with about 40-50% more clamping force. Although the pedal is stiff, the engagement travel is much shorter making quicker shifts possible. Cable adjustment is much like a stock clutch with out the sensitivity to adjustment that the Clutchmasters units exhibit. This clutch is less sensitive to overcentering than any of the other clutches mentioned here also.

Clutch Specialties uses a stock Nissan disk, but other custom disc and dual disk options are available. This company seems like a new viable alternative. Speak to Brian Holtkamp for your needs there. The phone number is (714) 525-4272. These guys also make clutches for anything. If you want a full metal 3-puck for your model -T it can be done here!

Dynamic Autosports / Redline
The Double D clutch is basically a stock type pressure plate with two diaphragm springs. This is one hard hitting, mean griping clutch, especially with a 3-puck disc. It has a high pedal effort and may not be too good for your motors thrust bearing for long term street use.

For full race use the DD should be pretty good. Manny Gonzales has used this clutch on his mega nos, slicked up 12 second SE-R which may be the fastest SE-R in the country. I personally have no experience with this clutch but Manny swears by it.

ACT, RPS and others
I have no data or experience with these. I am not even sure if they make SR-20 clutches. Hopefully the tech information I listed here should help you make a decision with these brands.

Lightweight Flywheels

Lightweight flywheels are an easy way to gain some acceleration. Normally the flywheels job is to store some potential energy to help the car get underway off of a standing start. However once the clutch is out and the car is moving, the flywheel is dead weight inhibiting acceleration because of it’s rotating mass. Contrary to popular belief a lightweight flywheel does not give you more horsepower, but improves acceleration. This could possibly register as a gain on an inertial dynamometer like a dynojet. A general rule of thumb is that one lb. off of the flywheel is like 20 off of the car. I have never bothered to calculate to see if this is really true, but a light flywheel is a very feelable difference in 1 &2 gear. For normal driving you have to rev your motor slightly higher than normal and slip the clutch a little more when getting underway as the car will be slightly easier to stall but you will get used to it quickly and it soon becomes a non-issue.

Most of the aftermarket light flywheels available for our cars fall into the 9-12 lb range. The stock SE-R flywheel is about 18 lbs. In my experience you do not want to go much lighter than 9 lbs in a car that is driven on the street or drag raced. One of my cars had a 5 lb. Tilton flywheel and that car was impossible to drive smoothly. Excessively light flywheels will bog out of the hole in a drag race start also. You will probably need to raise your launch rpm somewhat with a light flywheel to prevent bogging out of the hole. Road racing cars need as light of a flywheel that is possible to make to get the most throttle response and acceleration out of turns.

Autocrossers have told me that a Light flywheel can be worth as much as 1-2 seconds on a minute course. I am not sure than SE-R will respond so well but I guess it is possible on some cars.

Lighter weight flywheels lose there momentum faster when the clutch is pushed in and the gas is let off, this makes the syncros in the transmission’s job easier. Slightly smoother shifting and longer syncro life can be expected with a light flywheel.

Currently there are two types of flywheels available, steel and aluminum. JWT, Stillen, Clutchmasters and Mueller Fabrication all have trick aluminum flywheels that are just about identical in construction and quality. I have no preference between these units and would just order the one which is priced the best. My current flywheel is an 11 lb. Clutchmasters but any of the other companies offerings should perform well. JUN’s offering is quite different than the others being made from a high quality steel forging.

The aluminum flywheels are all very high quality and look pretty identical to me. With the exception of the Stillen unit, they are machined of 6061-T6 aluminum billet which is a very high grade of heat treated aircraft aluminum. The Stillen flywheel is machined from 7075-T6 which is a non-weldable aluminum which is of even higher strength than 6061. These flywheels use the stock steel starter ring for durability. All of the aluminum flywheels have a replaceable steel friction surface for the clutch disc to rub on. I believe all of the aluminum flywheels are close to 11 lbs but Mueller and Clutchmasters are willing to make custom weight flywheels to order. The major advantage to the aluminum flywheels is that you can change the steel friction surface and starter ring, effectively rebuilding the flywheel if necessary. This is an important feature if you are running an abrasive all metal clutch disc.

The JUN unit is a totally different design of flywheel. The JUN flywheel is a beautiful work of art, forged from 4340 hi-nickel chrome -molly steel. 4340 is a highly ductile, tough steel alloy that is used for things like axles and gears. It is not weldable which makes it an excellent candidate for this application. Forging is mashing a hot billet of this metal into a die at very high pressures. Forging causes good grain compacting and orients the grain of the metal in the proper direction for ultimate strength. A good advantage is that the starter ring gear is forged in place and hence, much stronger than the stock type ring gears used on the aluminum flywheels. Overall the JUN unit is probably much stronger and can take more abuse that the aluminum units.

The JUN flywheel is available in 9.5 and 10.5 lb. weights. The lighter of the two is milled around the periphery to get the additional one lb. less weight. About the only disadvantages of the JUN unit is that it cannot be resurfaced much more than one time which is an issue for those that run a full metal disc. The ring gear of the JUN flywheel is also non-replaceable. On the other hand, due to the forged in place ring gear teeth, they are more durable.

Contrary to popular belief, streetable light flywheels will not affect your engines idle quality. Super-light button, full race units may have some idle stability issues but these types of flywheels are found on things like Indy cars, not your typical speed shop.

Other Drivetrain Modifications

JWT motor mounts
The stock Nissan motor mounts on our cars are seriously lacking in the performance department. Designed to cancel engine vibration and drivetrain snatch, they seriously fail to contain the drivetrain gyrations that hard driving and/or modified motors puts through them. An almost universal failure on our car is the motor mounts. Almost everyone I know with a built SE-R has had problems with them. The ones on my car failed after just a few dragstrip launches. When the motor mounts begin to fail the engine really starts to flop about in the engine compartment, producing incredible wheel hop. This wheel hop is very damaging to other driveline components such as halfshafts, the clutch and worse still, is the main cause of the dreaded transmission case cracking that plagues high powered SE-R’s. The flexing motor mounts literally let the transmission pound on the crossmember until the case cracks. Wheel hop also ruins 60 foot times as the car cannot get traction well.

The stock motor mounts are made of a soft rubber with window cutouts designed to let the motor have additional movement. These soft squishy mounts are one of the main reasons that the SR-20 seems so silky smooth. Unfortunately these soft mounts were not designed to withstand high-revving, clutch -dumping dragstrip like starts. With a modified motor the flexing mounts are overstressed to the point where the can induce wheelhop even while cornering. When watching my car with the hood open on the dynojet, I was surprised to see the motor move at least 3 inches under load! The stock torque retaining strap allows about inch of movement before it’s internal bumpers even come into contact with anything to begin to restrict fore and aft motion.

So far there is only one solution. JWT makes a set of heavy duty mounts. These mounts are made of a very hard, high durometer rubber. The JWT mounts are also solid with no flex-inducing cutout windows. The JWT torque retaining strap is also solid rubber internally so it resists motion from the get go.

The JWT mounts eliminate wheel hop and improve throttle response by getting all the lash out of the drive train. All the crashing and banging of the engine and exhaust system under hard launches is eliminated also. I believe the JWT mounts can greatly reduce the chances of the transmission case cracking and even reduce the chances of the headers cracking.

The main drawback of the JWT mounts is that they let a lot of vibration through into the cabin. The silky smooth idle of the SR-20 will be replaced with a more truck-like vibration. Once underway the vibration difference is not so noticeable but idle vibration is definitely rougher. You can mostly feel the difference through the steering wheel.

Some list members have complained that the increase in vibrations make their cars rattle. I have not experienced that but I do notice that loose change in the ashtray or CD cases in the glovebox can rattle at idle. The level of vibration is probably not acceptable to the average driver but the enthusiast driver will probably like the improvements in throttle response, the elimination of wheel hop and the reduced possibility of breaking stuff enough to put up with the vibration.

I’d say that for those with heavily modified engines or drag racers the JWT mounts are mandatory.

Nismo Viscous Limited Slip Differential
Nissan Motorsports sells an improved viscous limited slip differential for pre 97 SE-R’s. Unfortunately it will not retrofit into the 98 non viscous transaxles as the viscous units have much bigger side case bearings requiring a different transmission case.

The Nismo VLSD is identical to the stock one except it has 20% more lock up than the stock differential. This is important if you have a high horsepower car. On my SE-R the inside wheel still spins pretty bad coming out of turns even with the stock limited slip. The VLSD should also help for drag racing when you want the maximum torque going to both wheels. On our IMSA SE-R, we gained two seconds a lap when we went to this differential.

The stock VLSD also wears out. If you are a serious road racer or autocrossers, the viscous fluid breaks down after a while and the stock diff works less well. When rebuilding the tranny, it might be a good idea to add this unit.

The only drawback is the price which is about $700. I will be adding this unit to project SE-R soon and Searl’s turbo monster will be getting one.

Case Welding
The pounding the transmission case gets from the stock motor mounts allowing it to beat on the crossmember during drag racing launches often causes the transmission case to crack. Typically the case cracks from the shift linkage hole to the axle hole. The case can be rewelded and reinforced in this area. JWT rewelds the case from the inside by cutting a piece of aluminum to bridge some internal webbing inside the case and TIG welding it in place. John Davis of "Orange Krush" fame does the same thing except he welds the reinforcement on the outside of the case.

Either way one should weld slowly to prevent any chance of the case warping. This mod is not necessary except for very high horsepower cars with slicks. Using the JWT mounts can reduce or eliminate the chances of this happening in the first place.

Quick Shifter or Short Shifter
Although the SE-R has a direct rod, slick-shifting shifter from the factory, it still falls short of the excellent shifting action exhibited by Hondas and Acuras. The SE-R suffers from a fairly long shifter throw and a slightly vague feel. With the help of the aftermarket this can be corrected. Basically there are two types of short shifters on the market for our cars, the SMC / Pacesetter and the Stillen. Both of these shifters work by eliminating the stock rubber shifter bushings, replacing them with hard plastic and by altering the motion ratio, allowing for a crisper feel and shorter throw.

The Stillen short shifter is an impressive piece of work. The shift ball and retainer is machined from a solid piece of billet aluminum. It is smooth and precise. The best thing about the Stillen shifter is that it is easy to install. Being a complete unit, it simply drops in place of the stock shifter. The Stillen shifter has been known to have a slight rattle which can be cured by liberally greasing the shifter ball occasionally.

The SMC/Pacesetter shifter is basically the same unit. It was designed by Steve Christensen of SMC and manufactured by Pacesetter. SMC packages the shifter with a weighted leather knob and Pacesetter features a machined aluminum knob.

The cool thing about these shifters are that the throw can be adjusted by changing the shifter motion ratio. This is accomplished by screwing the pivot ball up and down the shifter shaft. The SMC/Pacesetter is not known to rattle either. The drawback to this shifter is that the installation is more difficult. This shifter uses the stock shifter socket so the stock shifter must be completely removed from the car, disassembled and the socket must be reused.

Despite the difficulty installation, the SMC shifter is slightly smoother in operation once all is said and done.

Lubricants
The proper lubricant selection for your transaxle can make a huge difference in shifting ability and component life. Basically in my experience synthetic lubricants are the best for the gearbox. The transaxle of the SE-R has some different lubrication requirements from the typical differential/transmission combo that RWD cars run. RWD cars can run a different lubrication sump for the transmission and the gearbox. This is good because the sliding hypoid gears of the ring and pinion require an oil that is as slippery as possible for long life. The transmission however has some unique requirements. Since the gears of the transmission are pushed into and out of mesh, sometimes violently, it is important that transmission fluid have cushioning properties. Transmissions also have syncromesh cones that spin the selected gears up to matching speed so they can mesh without grinding. It is important for these cones to be able to grip each other for positive synchronization and quick shifts. To work properly, a transmission lube must have the diametric properties of preventing metal-to-metal contact in the gears and bearings, but allow metal to metal grip in the syncros.

Typically gear oils like the ones used in differential cases of RWD cars have lots of what is called extreme pressure additives. These are Zinc, Sulfur and phosphate bearing compounds that actually form a sacrificial layer on metal parts under high pressures and temperatures, preventing metal to metal contact. Extreme pressure additives are the stuff that makes gear oil smell so bad.

Unfortunately EP additives alone or super slippery synthetics can prevent the syncros from gripping, causing balky shifting and grinding. Thus good transmission lubes contain, in addition to EP additives stuff called friction modifiers. Friction modifiers are fatty acids that somehow allow the fluid to have metal-to-metal contact under the differential in speed shear conditions that syncros experience. I don’t understand the chemical mechanism exactly but it may have something to do with thixotropic (which means thins out under agitation) properties of fatty acids.

The best transmission lubes have a synthetic base. Synthetics have very stable viscosity for consistent shifting even in very cold weather. Instead of being made of refined crude oil, synthetics are made of esters. Esters are heavy long chain molecule alcohols. The strong, stable organic bonds with the long chain molecule is what contribute to synthetics high film strength and long life. Synthetics also have a very high film strength and resist degradation. A good Synthetic lube will actually help shifting and reduce wear.

Many list members like Redline MTL. Redline MTL is very light bodied for minimal viscous drag. It could save a horsepower or two. Because of it’s low viscous drag, MTL has been a showroom Stock racers trick for years. MTL has a good friction modifier package for excellent syncro action. I have found that a transmission with worn syncros and crunchy shifting can sometimes be restored to slick shifting with a change of fluid to MTL. I have found accelerated gearbox wear on race cars using MTL. Sometimes an old worn transmission can start to rattle on MTL because of it’s light body.

The guys at Nissan Motorsports have used Redline Shock Proof gear oil with good results. It is similar to MTL but with a heavier body. The shock proof has helped cure some chronic transmission breakage problems for them.

On my street cars I used to run Mobil One gear oil but have found that the shifting action is not quite as good as the MTL.

Recently, I have discovered Motul gear oil. Motul seems to work extremely well. It is heavier bodied than MTL and seems to shift just as well. Gearboxes seem to hold up better in race conditions with Motul also. We have tested Motul in our Speedvision 240SX and it seems to hold up well. The Motul that works the best is Motul Gear 300 which is an all synthetic 75-90 weight oil. Some other listmembers have had good luck with Motul 80-90 gearbox which is a mineral oil that is highly fortified with EP additives and Friction Modifiers. Other listmembers have had good luck with Motul gear 75-90 which is a semi-synthetic.

To get the minimum in viscous drag NEO makes a ZERO weight synthetic gear oil. This was designed to be used for showroom stock racing where every little bit of power is important. I am afraid to even try this stuff so I have no opinion of it.

Shotpeening and Cryo treatment
SE-Rs are not known to break their transmission parts but as the development curve rises it is inevitable that it will happen. Shotpeening is the bombardment of a metal part with steel spheres at a controlled velocity. Shotpeening mircoforges the grainstructure of metal in the first few thousands of an inch on the surface. This creates a tough skin on the parts that cracks cannot propagate in. Shotpeening can improve the fatigue strength of a part by over 100%. I have used shotpeening to solve many drivetrain breakage problems. Shotpeening has cured axle and gear breakage in cars that I have been involved with. Shotpeening is cheap. All of the shafts and gears in a tranny can be shotpeened for under $100. It works really well for halfshafts also. A place that is aircraft certified is the best place to get your shotpeening done.

Cryo treatment involves soaking metal parts in liquid nitrogen and letting them slowly return to room temperature. It is supposed to make a big difference in abrasive wear and toughness of parts. It’s cheap but I have never tried it before.

Troubleshooting

Here are some common problems with the drivetrain and some trouble shooting tips.

Clutch Slips
Well, its probably wearing out. Sometimes this can be caused by cable adjustment. Go to the arm where the clutch cable connects to the throwout fork of the transmission. Wiggle the cable, it should feel slightly loose. If it is drum tight loosen the lock nuts and put a little play in it. If the clutch stops slipping you are most likely ok for a while. Otherwise you need a new clutch. A few listmembers have destroyed there new Clutchmasters clutches by having the cable too tight and driving around with it slipping. A too tight cable also promotes overcentering where the pedal sticks to the floor at high RPM’s. If your car has more than 150 wheel horsepower, it probably needs a HD clutch!

Clutch Pedal is suddenly real stiff
The clutch cable is wearing out and is about to break or needs lubrication. Try removing your cable and shooting break-free or dri-slide into one end until it drips out of the other. If this doesn’t help , you need a new cable.

My clutch pedal sticks to the floor when I speed shift
Your clutch is overcentering. You need to reduce the cable pull so the clutch pedal will only pull enough cable to disengage the clutch.

My car grinds when I shift
Several things can cause this. If it grinds or shifts real stiffly in every gear, I would investigate to see if the clutch cable adjustment is allowing full disengagement of the clutch. If that is ok, the pilot bushing in the crank may be wearing out. If it grinds when only going into one or two particular gears which can be prevented by double-clutching, the syncros may need to be replaced. Sometimes marginal syncros can me stretched a while by going to Redline MTL. A long shot but a sometimes occurrence is that your throwout bearing arm or pivot has bent, check it.

My clutch won’t disengage even when I push the clutch pedal in
If the pedal feels slightly stiff but otherwise normal, a disc hub spring has probably broken out and is wedged in the pressure plate. Suspect this if you have an early Clutchmasters clutch or a stock clutch. In extreme cases the diaphragm spring has broken. If this is the case the pedal gets real soft. This failure is not very common. Sometimes the throwout bearing arm or pivot bends or breaks.

The clutch pedal offer resistance to pushing but the car won’t move, like it’s in neutral
Bad news, your clutch disc has burst. Replace disc and any other damaged parts.

My transmission makes a whirring or rough rumbling noise that goes away or changes when I push in the clutch pedal
The input shaft bearing is beginning to wear out. The transmission is in need of a rebuild.

My car pops out of fifth gear
The baulk ring and syncros for fifth gear are worn out. These are prone to wear out at around 80-100k miles depending on your driving habits. This usually only happens on 91-93 cars. Later cars have improved parts in these areas. Replace these parts with the latest service parts. Badly worn motor mounts can cause this problem also. Click here for more info.

My short shifter rattles
Check to see if the shift linkage is contacting the catalytic converter heat shield. Bend the shield for clearance. If you have a SMC shifter adjusted for minimum throw, you may have to cut the shield away for clearance. A SMC shifter at minimum throw may contact the front antisway bar. You may have to adjust it higher so it won’t hit. A Stillen shifter may contact the side of the hole cut in the floor for the shifter. Grind away the contact area with a dremal tool, file or die grinder. A dry Stillen shifter can rattle. Reapply some heavy duty grease.

There is not enough thread on the clutch cable free-play adjuster to get the clutch to fully disengage
This is common on Clutchmasters clutches due to a slightly lower diaphragm spring. The secret is to lose one of the lock nuts on the freeplay adjuster on the transmission end of the clutch cable so you can get another inch or so of cable pull. If you want to get sano, you can make a spacer to go on the clutch cable bracket to take up some excess freeplay and put the cable adjuster smack in the center of it’s travel. Really worn clutch cables stretch quite a bit too. You may need to replace the clutch cable. Be careful and leave about of an inch of freeplay in the cable or you may run into overcentering.

My tranny is leaking gear oil, all the seals look ok
Check to see if the case cracked. Look at the area from the shift linkage hole to the axle hole. This is the place where it usually cracks.

My car shifts sort of stiff, especially in cold weather
The trans fluid is shearing down, try one of the synthetics mentioned previously, Redline or Motul.

My brand new kevlar disc judders
You either did not resurface the flywheel correctly or contaminated the disk with fingerprints, oil or grease. Remember kevlar and metal disks must be carefully resurfaced and broken in with easy driving for 500 miles. Any fingerprints or oil must be carefully cleaned off with contact cleaner or brake cleaner before installation.

My metal disc judders
This is normal, metal discs have no marcel spring. Metal discs must be carefully broken in for 500 miles of easy driving.

My solid hub, all metal, three puck disc clutch judders and jerks real bad
This is normal. A race disc in not streetable.


Well, I hope this answers all of the clutch and drivetrain questions that keep popping up on se-r.net. Drive safely and keep the pedal to the metal!

Reader's Contributions

red_triangle.gif (202 bytes) Pat Griffith writes:

I had a Centerforce clutch on my old SE-R for 48,000 miles (sadly, the car didn't outlast the clutch). I had 200+ drag strip passes on it, 2+ hours on a road course and 7-8 autocrosses, and it always clamped hard.  I think one of the reasons I had such good luck with it -- compared with some other SE-R pilots' experiences -- was that I *always* did lift throttle shifts at the drag strip, and I never rode the clutch too much when launching the car. And no burnouts either.  I was always pretty smooth with the shifts whether it be on the track or on the street.

However, Mike did mention overcentering on the Centerforce and how adjusting the clutch cable was necessary to combat this. Every couple months or after 25 or so runs at the drag strip, the engagment points would be "off" slightly. I became an expert at removing the POP charger and moving the MAF out of the way so that I could adjust the clutch cable. :) So if you have this clutch or are thinking about getting it, you'll have to be sensitive to any sudden changes to clutch pedal feel.

I'm going to replace the stock clutch on my new SE-R and have again opted for a Centerforce. This time, I'm throwing a lightened flywheel (JUN) into the mix (not to mention launching with drag radials at the strip), so we'll see how this clutch holds up.


red_triangle.gif (202 bytes) Manny Gonzalez writes:

I happen to like ACT's kits. Everyone who orders one already knows more about them than I do. It seems that the customers have already done all the research. A few things that set the ACT kits apart from the rest are... 1. All new parts are used. 2. The pressure plates for SR20DE's have a 42% increase in pressure, without any increase in pedal feel. 3. Release clearance is an important issue in order to maintain fast clean shifting. 4. The Extreme puck discs contain a copper ceramic lining that holds approximately 28% more torque capacity than an organic lining. 5. The Extreme discs themselves are made of lightweight aluminum for quick shifts. 6. The Extreme 4 puck discs engage smoother than most of the competitions 6 pucks and 9 pucks. 7. The same can be said of the Extreme 6 puck,..real smooth engagement.

Basically for a daily driven vehicle that is running a 50 shot or more of NOS, I would recommend the 6 puck ACT kit. I wouldn't do this for other clutch kits.....the 4 puck is more for the individual looking for a smooth engaging kit capable of handling 300ft lbs of torque. All the ACT kits are unsprung, except for the street disc, so no worries of broken center sections or springs. Just in case you're wondering, I will be going with an ACT kit in my 400 HP DSM. The reason that I sell both the ACT kits and the Redline PRO kits, is because I wanted to give people an option. The Redline PRO kits will outlast the ACT kits by far due to the lining material that is used (100% woven Kevlar AKA "Clutchtechs") as long as they are matched for the right application, the Redline PRO kits are heavier also, but the ACT kits are for the no nonsense person looking for the ultimate lightweight, fast shifting, high performance clutch.


red_triangle.gif (202 bytes) John Davis Writes:

Here are instructions on how to reinforce your transmission case to prevent the infamous transmission cracking problem that seems to plague high powered se-r's.  JWT Mounts help immensely and this case welding tip from John Davis AKA Mr. Orange Crush should make for a bullet proof transmission.  JWT Performs a similar mod on local cars.

You need to find someone who can tig weld aluminum well first.   If you look at pass axle side of the case by the seal there are lots of casting gaps and ribs in the case there.  This is where cracking occurs.  Fill in gaps around seal and the gap on the bottom of case.  Also weld a thick aluminum bar across bottom.  It worked for me even w/o JWT mounts.  One other thing, welding should be done slowly to prevent it from warping.  I also did it with the trans still assembled b/c I thought if I got the bell hosing welded separately that it'd get warped.   All I did was to remove passenger side axle seal. Worked really good, never had one crack again.