Drivetrain: AWD System

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Written by: Bret Brinkmann

The purpose of this topic is to inform members about the weak links, diagnosis, maintenance, and upgrades for 3/S manual AWD drivetrains. References to part suppliers, TC recall info, and rebuild instructions will be listed through out the topic and at the end. If you do not know how a transmission works, then I highly recommend you learn. A good web site (although a bit too technical for most newbies I feel) is It deals with our drivetrains specifically. If you know of any other sites to help people understand the basics of transmissions or find errors in this topic please let me know and I will fix it.

Which version do you have?[edit]

There are three versions of the 3/S drive train. The first is the 5-speed 18 spline output shaft, which came on 3/S's up to the production date (not to be confused with what year the car is) of 11/91. The transfer case (TC for short) has a cast aluminum front housing. The second drive train is the 5-speed 25 spline output shaft, which came on cars produced between 12/91 and 5/93. The TC for this drive train also has a cast aluminum front housing but the 25 spline output shaft is larger in diameter. The third and last drive train produced came on 3/S's manufactured from 6/93 to the end of production in 99. These drive trains had a 6 speed with the same 25 spline output shaft used in the 5 speed, however their TCs had a cast iron front housing.

It should be noted that even given these production date cut offs you may still have a transaxle that is not supposed to be in your car. This may be due to any number of reasons none of which make a difference to you now. But NEVER assume you know what you have until you check. Obviously you can easily tell if you have a 6-speed or not. If you have a 5-speed then you need to figure out which output shaft you have. The only way to do this is by removing your TC and counting the number of splines on the output shaft. It will be either 18 or 25. Don't think you know what you have, check it for your self.

J-spec gears[edit]

While the 5 speed drivetrains are the same around the world, the J-spec 6 speeds differ from the US and Euro spec 6 speeds in that the J-specs have a numerically higher (shorter) final drive ratio. These gears have been dubbed "MR gears" but they actually came on ALL Japanese 6 speeds. It should be noted that a lot of Euro 3/S's were imported from Japan and thus also have the J-spec gearing. Currently, track times suggest that the J-spec gears will actually slow you down in the 1/4 mile until you start to run in the low 11's high 10's, at which point you begin to break even. They will not make your car faster until you run mid 10’s or faster.

If you would like to convert to J-spec gears (these gears only work with 6 speeds), then you will need the front diff ring and pinion gears inside the J-spec 6 speed tranny as well as the rear diff ring and pinion gears from any 5 speed rear end. The J-spec front ring and pinion gears are unique to the J-spec VR-4s while the rear ring and pinion gears are the same as the 5 speeds. Most members just swap out the whole 6 speed rear end for that of a 5 speed. The front diff ring and pinion gears from a J-spec tranny can be purchased from Kormex. You may also be able to get a hold of these gears if you can locate a member from Japan or Europe who is parting out/selling a J-spec tranny. YOU MUST DO BOTH SETS OF GEARS AT THE SAME TIME OR VARIOUS DRIVETRAIN FAILURES WILL OCCURE. The tooth count on the J-spec ring gear is 51 teeth and the pinion gear has 15 teeth.

Weak links[edit]

The first weak link that has been found is in the 18 spline drive train. It is the 18 spline output shaft. People have been able to snap this shaft in two with just a few basic mods like MBC, gutted cats, and intake. Over time and repeated launches it will break. Either way you will need a new output shaft.

The second weakest link is for 5-speeds in general, the cast aluminum TC front housing. They will tend to break along the backside into two halves. The crack will originate at the bottom section near the Getrag cover. The spreading force between the TC gears during a hard launch is the cause of this failure. Shock loading due to your launch technique also plays a big roll in this. I have heard of even stock cars breaking their housing over time with repeated high RPM clutch dumps. This failure has been known to break a piece off of the bell housing also.

The third weak leak is also found in all 5-speeds. After the front housing is strengthened/reinforced the cast aluminum TC mid housing will begin to flex from shock loading and gear spreading forces. The resulting flex will lead to the mid housing cracking and trying to shoot out of the back of the front housing. While this failure does not usually result in bell housing damage, it almost always results in the TC gears striping their teeth. Keep in mind that if the amount of power your car is putting down requires you to eliminate the first two weak links, then you are probably not far from experiencing this kind of failure as well.

From this point on, the failures do not necessarily occur because the parts are weak, but more so due to your launch technique and your set up. One such weak link is for all versions of the 3/S drive train. It is the VCU in the center differential. With the higher powered cars, the front and rear axles tend to spin at different rates during a hard launch causing the VCU to try and kick in but is simply over powered and it heats up until it fails and pukes it's viscous goo out into your transaxle's gear oil.

For 6 speeds, many members with around 350 AWHP or high 12 second quarter mile times or faster, have been breaking their bell housings during a launch over 5000 RPMs. This can also result in a broken transaxle mid housing, end cover, and several chipped teeth off of the input shaft, counter shaft, and 1st through 3rd gears. If this happens to you, then you may be financially better off getting a whole new 6 speed rather than rebuilding. A combination of shock loading and gear spreading forces are to blame for this. It is important to remember however that many members have ran 10s with 6 speeds countless times with no failures of this nature. Launch technique has a lot to do with weather or not you will experience this kind of failure and when you experience it.

There have also been a few reports of members snapping their front diff carriers in two on high RPM (think 5K and up) clutch dumps on both 5 and 6 speeds. Again, shock loading is the cause of this failure and your launch technique plays a big roll in when it will happen as members have been running countless 10 second quarter miles with out their front diffs snapping. There are two versions of the front diffs. One is a cast iron carrier and the other is a steel unit. All of the failures are on the cast iron units.

It should also be noted that both 18 and 25 spline shafts are subject to rust and corrosion of the splines over time as are the TC input spools. This will weaken the splines and will eventually result in the splines being striped. Applying some grease or other rust inhibiter to the splines of the shaft whenever you remove your TC can prevent this. (Like when you go and check which output shaft you have.)

Launch technique[edit]

With so many drivetrain failures occurring during or just after the launch, it is important to take your launch technique into consideration as to how much unnecessary stress you may be putting your drivetrain though. I see and hear of a lot of members launching their cars above 5000 RPMs but very few of them actually NEED to. I would highly encourage members to experiment with how low of an RPM they can launch their car with out bogging. I know a lot of members don’t want to risk bogging at the line, which could cost them the race, but at some point you need to learn to launch your car with out the risk of breaking some thing. More importantly to members on a budget, “abusive” launches can break your drivetrain resulting in an automatic loss of the race in addition to you needing to spend a lot of money to fix your car.

Any member with the stock 9b TD04 turbos should not need to rev past 3000-4000 RPMs on a launch to get good 60' times at the track. To help you find out your best launching RPM, start launching at lower RPMs and work your way higher. This will help you prevent any drivetrain failures as you learn. You should also experiment with how fast you let up on your clutch, as each clutch is a little different. As a basic guide line for how fast/slow you should let up on your clutch, most members get good results by letting up slowly at first until they can feel the clutch just starting to engage, and then letting it up faster as they feel the car begin to roll forward. Letting the clutch slip a little just before/during the launch to pre-load the drivetrain will also help take up the slack to reduce or even prevent shock loading which will help prevent a failure even further. Before you purchase an aftermarket clutch however, I advise you to do some research not only on it’s holding power but also what kind of launch technique members are getting good results with and buy one that can handle slipping as some clutches can fail relatively fast if subjected to slipping for even a small amount of time.

Another product to carefully consider before purchasing is a light weight flywheel. Light weight flywheels are good for enabling a car to put down more power however you should know about the give and take relationship that comes with a light weight flywheel. With the reduced flywheel mass, your engine will also be able to increase its RPMs at a faster rate. The “take” part of this relationship however, is that it’s reduced mass also means it is easier to slow down. What this means for you is that at the drag strip, your engine will be more sensitive and more likely to bog. You can compensate for this by raising your launching RPMs but keep in mind that higher RPM launches are more likely to break parts. Members wanting a lightweight flywheel should seriously take this into consideration before purchasing a flywheel for their car if it will see a lot of time at the drag strip.

Beefing up the drive train[edit]

Output shafts[edit]

You can replace the 18 spline output shaft with a new OEM 18 spline shaft but that will fail also. Especially with increased power, which you know you want because, that is why you are a member of 3Si. Kormex sells a hardened 18 spline shaft but it is not enough of a strength increase to prevent future failures. Many members have converted their transaxles and TCs to the stronger 25 spline set up. (The output shaft goes into the TC and thus the TC would also have to be converted to a 25 spline.)

The parts that will need to be swapped out include the 25 spline output shaft, output shaft seal, TC input spool, sun gear, VCU, pinion shaft, and transaxle bell housing. If you have an 18 spline TC with out the bolt near the center of the “Getrag” cover, then the front TC housing, passenger side bearing and input gear will also need to be swapped out along with the TC spool as one of the bearing bores in the housing is a larger diameter for the 25 spline spool and the hole in the gear for the spool is also larger in diameter. (More info is bellow on TC housings/spools.)

A few other members have swapped out for the entire 6 speed drive train. This is by far the most expensive way to beef up the drive train as you will need the entire transaxle, TC, front third of the drive shaft, and rear differential assembly. Some people need the shifter cables and some do not. If you wanted, you may be able to save money on the 6 speed conversion by swapping out the front diff ring and pinion gears for those from a J-spec 6 speed. This way you could still use your 5 speed rear end.

The most cost effective 18 spline up grade, even though it cost $600, is a shaft made out of a different material called the Mark Williams 18 spline 300m shaft. The 25 spline versions are also available. Even though it is still an 18 spline shaft it is made out of a much stronger alloy of steel. (Rockwell hardness of 55.) Thus far, it has proven to be just as strong as the 25 spline output shafts. (No 300m Shaft failures have been brought to my attention.)

When upgrading to a 300m shaft you should be aware that 300m has a higher tendency to rust than the OEM steel and therefore it is a good idea to keep the splines of your 300m shaft thoroughly covered in grease to help prevent rust which can lead to even a 300m shaft striping. Also keep in mind that when an output shaft fails it can take out the VCU with it. So if you have a snapped or stripped output shaft, then check the condition of your VCU when you swap out the shaft.

North Bend Tech also sells a 25 spline output shaft made of a different and stronger material than the stock shaft called quadco XR. While it has the same Rockwell hardness rating of 55, it is slightly stronger than 300m. It also comes with an anti-rust/corrosion coating to help prevent the splines from striping.

TC spools[edit]

Usually when an output shaft breaks or the splines strip, the splines on the TC spool will be damaged also. While in some cases you can get away with replacing the output shaft only, you will be better off in the long run to replace the output shaft and TC spool at the same time. Worn splines on either the shaft or spool can quickly wear out the new splines of your new spool or shaft even if they are made of a stronger than stock material.

Kormex sells replacements for all versions of TC spools. They used to sell a custom spool to convert your 18 spline small bearing TC into a 25 spline TC. However it is no longer available. So if your TC has a 25 spool it could still be a small bearing housing. So look for that check plug on the cover and if you are still not sure, then check the numbers on both of the bearing races on the spool. North Bend Tech sells quadco XR spools for the 25 spline 5 speeds and the 6 speeds. The North Bend Tech spools also come with the anti-rust/corrosion coating that their output shafts have. Mark Williams also sells 300m TC spools for 25 splines.

TC housings[edit]

All members who own an AWD 3/S should read the TC recall it self. It is available with the rebuild manual that is linked further down.

There is a gear oil made by Red Line called Shock Proof. It is supposed to help cushion the lash between gears and thus reduce the stress on the TC housing so it won't crack open. I have seen several pics of member’s busted TC housings with this fluid. It doesn't seem to make a noticeable difference when it comes to safing the hosuings. Using too thin of a fluid can result in premature teeth failure though.

Some cast aluminum TCs will have a little metal bracket on the back bottom portion of the front housing. This bracket appears to be a brace to help prevent housing failure but isn't very effective. One member (Ray Pampena) made an additional bracket for the top portion of the TC housing. I was also told that he has busted seven of them. Still in the cast aluminum TCs defense, Ray's car is very powerful. Other members have attempted to make an upgraded bracket and have had varying degrees of success. If you would like to make your own bracket then I recommend checking out the links bellow. Post 106 will give some good info as to the effectiveness of various bracket designs. Post 1 has excellent pics of how the aluminum TC housings break.

A TC bracket is available through EK2 manufacturing. It is know as the TC “cage”. The quality is very nice (powder coat finish) and from the track results I have heard of, it helps prevent housing failures down to low 11’s. It is important to remember that this bracket is not an excuse to subject your TC to abusive launches. Contact 3Si member ek2mfg for info on pricing.

Maximal Performance makes both 5 and 6 speed TC braces. It should be noted that there have been no reports of 6 speed TC housing failures. The 5 speed TC brace is much less expencive than the EK2 cage but the design suggest they will not protect the TC as well. I have not heard of any track test with the product yet, but the quality is very good. They have a powder coat finish.

Nelson Performance Pro has 5 speed TC baces available. They have proven to get the same results as the EK2 cage but the quality is low. Most of them require "modification" to make them fit such as grinding at certain random places and enlargening of bolt holes. Each one is a little different than the previous. They come painted in various colors.

It should be noted that there are two different cast aluminum TC front housings that were produced. One can be converted to 25 spline and one cannot. There is one with a bolt off center on the side cover that says Getrag and one that doesn’t have this bolt at all. The one WITH the bolt can be converted by swapping out the 18 spline input spool for that of a 25 spline spool. The differences between these front housings (the middle and tail housings are the same for all 5 speeds) are the bearing diameters for the input spool and gear. The earlier 18 spline TC (without the bolt on the Getrag cover) use smaller diameter bearings than the later model 18 spline TCs (ones with the bolt on the Getrag cover). The later model 18 spline front housings are identical with the 25 spline 5 speed front housings and thus interchangeable. The earlier housings are known as the “small bearing” housings and the later ones are known as the “big bearing” housing.

To convert a small bearing 18 spline TC to 25 spline you would need a big bearing front housing and an adaptor ring so the big bearing housing will accept the smaller diameter bearing. You can also use these adaptor rings on the front SS TC housings. This will allow you to use your small bearing 18 spline gear, spool, and side cover with the big bearing housings instead of needing to buy their bearing counter parts.

The differences between the bid and small bearing gears and spools is the input gears are press fit (0.004-0.005 inch press fit) over the spools. The diameter of the hole in the gear and the outer diameter of the spool are a smaller diameter for the small bearing TCs. Thus, a big bearing spool cannot be installed into a small bearing gear and vise versa. However you may be able to get a trust worthy machine shop to machine the small bearing gear to accept the big bearing spool.

You should also know that some times when the TC housing breaks it may take a chunk of the transaxle bell housing with it. If your output shaft striped then you should replace the TC input spool also as it is usually weakened as a result. Some members swap out to a 6 speed because they get the stronger cast iron TC housing in addition to this conversion. Swapping to the J spec gearing also becomes a possibility with this conversion.

There are two different 5 speed front TC housings available to replace the stock cast aluminum one. The first is a billet aluminum housing and the second is a cast stainless steel housing. The billet housing is only available in the big bearing version. The SS housings are available in big and small versions. But if you want to switch to a 25 spline set up, then you will need a big bearing spool, gear, and the bearings on both sides of the spool. If you have a small bearing spool and need a replacement, now would be a good time to upgrade the housing as well.

The billet aluminum housings are made by a 3Si member whose user name is NoCar and are available with an optional brace. Do to the dimensions of this housing, after market braces will not fit and your only option will be the optional bracket that is sold with it. With out this brace your TC will be able to hold up to low 11 second runs but with the brace it can with stand at least low 10 second runs. The reason behind this is that the cast aluminum mid section of the housing begins to flex and then break just like the OEM front housings do. When installing the brace on the billet aluminum housing, you should take extra precautions to ensure that the nuts and bolts holding the brace on do not back off. Having personally installed one myself, I highly recommend using nuts with nylon threads and/or loctite yellow as they are more resistant to backing out and the use of blue thread locker has proven to be unsuccessful on many members’ braces. An added feature to this housing is that the fluid capacity of the TC is increased slightly adding a little more protection against TC lock up should you have a TC leak and not know about it. It should be noted that the fill plug is a smaller diameter yet the fill plug center is still at the OEM height. What this means for you is that you will be more likely to over fill your TC. This will result in a temporary leak around your breather and/or output seal until enough has leaked out so the fluid is at the correct level.

Here is a link to view the NoCar case. See post 128.

The cast stainless steel (SS) housings are made by LIPP performance. This housing will also allow you to run low 11s with out a TC housing failure but just like the billet aluminum one, the mid section will start to flex and then break. LIPP also sells a SS mid housing. With both housings installed, no one has experienced a TC failure. Again, this is not an excusse to abuse your drivetrain.

Here is a link to where the SS housings are sold.

Here is a link to a thread with good pictures on a mid housing TC failure.

Front, Center, and Rear Differentials[edit]

As the car is launched the weight transfers to the rear wheels. The reduced weight on the front axle results in less friction between the front tires and the road making it easier to spin the front tires than the rear. The OEM front diff is an open type diff. During the event of a slipping wheel the open diff will not be able to send more of the power to the wheel that is slipping than to the wheel with grip unlike an LSD can. So more accurately, you won't spin both of your front tires faster than the rear axle; you will spin ONE of your front tires faster than the rear axle. This will ultimately lead to the VCU in the center diff working at speeds faster and longer than it was designed to and it ends up over heating and failing.

Preventing wheel spin in the first place is easier than trying to correct it once it has already occurred. This will help your drivetrain last longer and result in quicker launches. Here are a few things that can help prevent and limit front wheel spin. The first is a good suspension set up. Keeping enough weight on the front axle will help prevent traction loss in the first place. Another thing you can do that is often over looked is to use stickier tires. Even basic power upgrades like a boost controller and gutted cats can lead to front wheel spin on a launch if the tires do not have at least an AA traction rating and some descent tread left. Bald tires do not give good traction no matter what the traction rating is. Stickier rubber will drop your 60' times as well as help prevent front wheel spin.

There are three options available for the front diff. Both Kormex and Super Car Engineering (SCE) offer a torsen type front LSD made by Quafe and Speed Freaks Racing has an LSD “insert”.

The Kormex front LSD, made by Quafe, replaces the whole OEM open diff assembly and looks to be significantly stronger. I have heard of several of the cast iron OEM front diff carriers snapping in two. Again, they both occurred on 5K or high RPM launches with the clutch dumped (the kind that may not be necessary for good 60’ times). I have heard of a couple of the Kormex LSD housing bolts backing out resulting in tranny damage. To prevent this I recommend you remove the housing bolts one at a time, apply some thread locker to the bolts, and torque them down to 18 ft-lbs. The Super Car front LSDs come with loctite already on the bolts and the bolts looks to be torque to yeild bolts. If they need to be removed on the SUper Car unit, they should be replaced. Another thing I noticed on the Kormex unit is that if you have to remove the ring gear bolts, they will come out slightly striped looking. For this reason I recommend that you replace the ring gear bolts should they ever be removed from the Kormex front LSD.

The Speed Freaks insert is significantly cheaper than the LSD units but does not replace the OEM front differential assembly. The “insert” consists of two thick rectangular plates with several stiff springs sandwiched between and pushing them away from each other. The plates are held together for installation by two sets of locking pins on opposite sides. To install the insert you remove the spider gear pin, insert the spring loaded plates (held together with locking pins for installation) between the side gears (thus the term LSD “insert”), reinstall the spider gear pin, and then remove the locking pins. This allows the spring force to push the two plates against each other pressing the side gears against the differential carrier which makes it harder for the OEM open diff to transmit all of it’s torque to only one wheel. Although much cheaper than the LSD units, these inserts have not proven to be durable enough to handle the stress that a hard core street car, drag racer, or track racer can dish out. After a moderate amount of time the inserts rubbing against the side gears will polish the contact surfaces between them smooth so that they loose their effectiveness completely. Some one who races their car frequently or can afford it would be better of with an LSD while some one who occasionally races and is on a tight budget would be better of with the insert.

The problem with the OEM front diff is that once you get one wheel spinning all the power to the front axle wants to go to that wheel. That in turn makes it harder on the VCU to limit the speed difference between the front and rear axles. With the addition of a front LSD, sticky tires, and a suspension set up intended for drag racing you make it harder for only one front wheel to spin thus the VCU doesn't have to work as hard and it won’t fail.

SCE also has a torsen type center diff for all cars and it comes with it's own 300m output shaft. The torque split is an asymmetrical 40/60 and makes the car easier to rotate while cornering as opposed to under steering while hitting the gas mid corner. The torque split can range between 20/80 and 60/40 depending on traction conditions. If you install one of these make sure any chasis dyno you use can support this asymmetrical torque split or you will damage your drivetrain. The torque capacity of this unit is 3789 ft-lbs for 5 speeds and 4008 ft-lbs for 6 speeds taking gear ratios into consideration.

Additionally, SCE offers a clutch type rear diff. It is a 1.5 way rear diff and comes with it's own gear oil. It is important to remember to use this specific gear oil as other fluids can damage it and/or cause additional problems.

6 Speed Bell Housing[edit]

As mentioned earlier, a 6 speed bell housing can crack during a launch with RPMs of 5000 or higher. However if you have turbos that require you to launch at these RPMs to prevent bogging, then reinforcement becomes necessary. One company that can weld a reinforcement plate to your housing to help prevent this failure is PO Machine. Here is a link to a thread with pictures and contact info.

Having installed one of these reinforced housings I would highly recommend that you double check your bearing preload and test fit your input shaft into the input shaft bearing before final assembly. Warping of the housing while welding this plate on can occur. As a result, you may find that you need to readjust your bearing preload and “modify” the bore in the housing for the input shaft bearing. If you experience any unusual problems feel free to send me an e-mail or PM and/or even call me at the shop for assistance.

Ray Pampena Motorsports offers a reinforcement rings for both 5 and 6 speeds that is not as large as the PO Machine plate but will not warp the housing. You can either send them your housing and they will weld it in or you can buy the brace and have someone else weld it in.

Shift forks[edit]

SCE offers billet aluminum 1/2 and 3/4 shift forks for the 6 speeds only. It should be noted that the OEM forks are not a weak point in these transaxles. Forks break as a result of dragging clutches, improper fluid usage, and/or poor driving skills. If the fork didn't break during a bad enough mis-shift (for what ever reason), then either other linkage components would become damaged, the dog teeth on the gears and synchro sleeve could wear out or even break, or the synchro ring could over heat and become damaged in one mis-shift event. When the dog teeth on the gear fail a new gear and synchro collar must be installed which cost more than replacing the OEM forks. As long as your clutch isn't dragging, your fluid provides good shift quality, and you don't mis-shift you will not have to worry about breaking a fork. I have mentioned the billet forks here because some members would prefer a billet fork and the OEM forks might not be available when some one needs them.

Synchro Rings[edit]

Kormex has a middle friction ring for 1st and 2nd gear for both the 5 and 6 speeds (they are interchangeable). They reportedly work just as good as an OEM ring. The design is slightly different than OEM but the friction material used appears to be the same. The differences are in the tangs and the oil grooves. The Kormex rings have a slightly deeper oil groove than the OEM rings. The Kormex tangs are square shaped while the OEM rings have rounded edges where they join to the main body of the ring. The Kormex rings have the friction coating on the tangs unlike the OEM rings but the tangs on the OEM rings appear to be heat-treated. The tangs on the OEM rings look stronger than the Kormex rings however it is important to keep in mind that the tangs on these rings, weather OEM or Kormex, are not known to break.

There are sets of non-OEM rings being installed in some transaxles that are made entirely of brass (believed to be from a Hyundai application). These rings are used in 3rd through 6th gears but not 1st or 2nd as those two gears have a different synchronizer design. It has been my and several other member’s experiences that these rings do not last much longer than a year at best, no matter what your driving style is like. This is mainly due to the fact that these rings are designed for use with a different type of fluid (probably an automatic transmission fluid of some sort) other than our OEM rings and different cones on the gears than our OEM rings. While you may get more life out of these rings by switching to a different fluid, you will still have the OEM style 1st and 2nd rings, which are not designed to be used with that type of fluid. Due to the different fluid demands of these rings compared to the OEM rings there is no fluid that will meet the demands of both styles of rings and you will be better off in the long run to avoid these non-OEM solid brass rings.

Maintenance and diagnosis[edit]

Most of you know the symptoms of a slipping clutch. If you don't then you will eventually. A broken output shaft, stripped output shaft/TC input spool, popped center VCU, striped VCU/sun gear/pinion shaft splines, broken or popped out front CV axle, broken rear third section of the OEM drive shaft, and/or a busted TC housing will give similar symptoms. The difference is that a clutch usually goes out gradually while these parts usually go out all at once. The only exception is if you are using a puck style clutch, which can also go out all at once. These failures are often misdiagnosed as failed clutches and members end up spending time and money for a part that won't correct the problem. Listed bellow are symptoms of these failures.

TC failure[edit]

You will usually know when your TC housing explodes because they literally go out with a "bang" during a hard launch. Most members report that they felt a thud by their feet when it happened. Of course with the case busted wide open all the fluid inside will spill out on the road. At the least, the front housing will have to be replaced. The extent of the damage will very on a case-by-case basis and can include the bell housing, TC middle casing, and the TC gears. Most members just buy a new TC from Kormex or another member and put new seals in it. The part number for the reseal kit from Mitsubishi is MN156006. Be sure to use the metal washer to press in your TC input spool seal so that the washer is flush with the housing. Failure to do so will result in the seal being flush with the housing (not recessed in the housing like it should be) and it may pop out, leak out all of the fluid, and cause your TC to lock up potentially causing an accident.

Output shaft and TC spool failures[edit]

If you are pretty sure that your clutch is good and your TC housing is intact then the next step is to remove the TC from the car and inspect the condition of the output shaft and the TC input spool. You should be able to tell right a way if the output shaft has broken or if some thing is striped. The splines on the shaft and spool should be trapezoid shaped not triangular. Usually the splines on the shaft will strip but they can damage the spool in the process. If you striped something then it is a good idea to replace the spool and the shaft at the same time. If you broke an 18 spline shaft then the most cost effective repair (and upgrade) is to get a Mark Williams 300m 18 spline shaft an 18 spline spool from Kormex. In either case, inspect the splines on the shaft and the spool to be safe. If they are triangular shaped then they are worn and about to strip. It they are trapezoid shaped then they should be good to go. Be sure to clean the splines and then apply grease or another rust inhibitor to the splines to help keep them rust/corrosion free.

Incorrect TC installed[edit]

On several occasions I have heard of people going in for a recall or they swap out their TC and then their car will have/still have these symptoms. If this is the case then pull off your TC and make sure you don't have an 18 spline output shaft going into a 25 spline TC. The 25 spline TC will fit over the 18 spline shaft due to the smaller diameter of the 18 spline shaft compared to the 25 spline shaft. In such a case the 18 spline shaft will spin freely inside the 25 spline TC input spool and the car will not move. You can usually hear a faint grinding noise coming from the floorboards.

VCU failure[edit]

Usually when the VCU in the center diff pops, it pukes the viscous goo out into the transaxle's gear oil. If you drain you tranny fluid, then look to see if it is blackish/brownish in color. The VCU goo will usually separate from the gear oil if it is sitting for a couple of hours. If you found goo in your gear oil, then you have a failed VCU. The car will still be able to move but members have reported that they get a lot of front wheel spin on a launch and their 60’ times increase as much as half a second or more.

Another more rare VCU failure is that the splines that mesh with the sun gear and/or the pinion shaft will strip. You will usually hear a clicking/ratcheting type of sound along with the usual slipping clutch like symptoms. You do not experience any wheel spin however. These symptoms are most prevalent in the lower gears.

Front CV axle failure[edit]

A front CV axle failure or a front CV axle that has popped out of the tranny can be easily diagnosed by looking at your speedometer when the “slipping” symptom occurs. If your speedometer registers an increase in speed, then inspect your front CV axles first. The reason your speedometer registers more speed is because the front diff carrier drives the vehicle speed sensor. The carrier will spin if an axle popped out or if an axle broke and thus drive the speed sensor faster. A front axle failure/popping out puts a lot of stress on the VCU also. So drain and inspect your tranny’s gear oil if this happens to you.

Drive shaft failure[edit]

The OEM drive shaft is made of three shorter drive shafts splined and bolted together. The rear third section is made up of three parts. There is a smaller diameter tube inside a larger diameter tube with a layer of rubber in between that holds them together. With enough power (estimated around 500 AWHP) or enough age to dry rot the rubber, the outer tube will separate from the layer of rubber that holds it to the inner tube and the tubes will slip against each other. This will heat up the rubber in between the tubes and partially melt it. It will then cool and hold the tubes together again but it will never hold them as strongly as it once did. It will hold them together strong enough so you can’t turn the tubes against each other by hand but the engine will be able to get them to slip with the greatest of ease. Here are two things to look for if you suspect this failure. First, it will be easier to induce slipping in the lower gears. Secondly, when slipping occurs it will feel like you are in a RWD vehicle that is stuck in the mud. You can feel the drive shaft spinning but you are not going any faster. You may hear a grinding sound from the rear during slipping but this symptom is not always present. This type of failure is also very hard on the center VCU and you should inspect the tranny’s gear oil for signs of VCU goo.

Rebuild manual and recommendations[edit]

To replace the output shaft and/or VCU you have to open up the tranny. I recommend you remove it from the car and put in new seals, synchros (if needed), and a clutch (if needed or stock) while you are at it. I highly recommend against pulling the end cover with the tranny in the car. I have had way too many members calling me up or sending me PMs/e-mails for advise about shifting problems, grinding noises, leaks, and cracked housings as a result of this practice. These tranny’s were designed to be taken apart bell housing first while out of the vehicle. Any other disassembly method can (and often does) result in further damage. The Getrag 440 (five speed) and 446 (six speed) rebuild manual can be downloaded from the thread linked bellow. Special thanks to Gatecrasher and all who helped in the translation for the hard work in making this information available to all 3Si members.

The torque spec for the input shaft lock bolt is for the 12 mm hex bolts only. It does not list a torque spec for the 7 mm hex bolt found on earlier 5 speeds. I have been torqueing them to down to about 20 ft-lbs with thread locker myself with out any problems.

Other commonly and not so commonly failed parts include the synchros, seals, and the occasional bearing and shift fork. These are almost always related to previous owners neglecting to change the gear oil on a regular basis and/or the clutch dragging for any number of reasons. The driver’s inability to properly shift gears fast will also cause a burned synchro or a broken fork (I know even I am guilty of poor driving abilities). While fluid and clutch issues will be addressed in other threads/topics I would like to caution members about tranny installation. When attempting to line up the input shaft with the clutch hub, DO NOT VIOLENTLY JIGGLE THE TRANNY. This will result in the input shaft beating against the clutch hub and warping the disk. A warped disk will drag and greatly increase the chances of synchro and shift fork failure.

Here are a few tips that have made mounting the tranny to the engine much easier for me. When installing a new clutch, you will notice that the clutch alignment tool has some up and down play in it when holding the disk against the flywheel. If you hold the alignment tool midway in it’s range of up and down play before tightening the pressure plate bolts, then it will better align with the tranny input shaft so you will not have to fight the shaft into the clutch hub.

The easiest way to get the tranny into position to mount it to the engine is with an engine hoist if available. Bolt the chain of the hoist to the shift cable bracket holes in the bell housing. This will balance the tranny and generally only requires you to slightly push it side to side to clear the cross member and any hoses or splash shields. The closer you get the tranny to it’s final position on the engine, the more it will naturally align it self to the engine. You should find that the tranny will slide easily against the engine once the input shaft splines are aligned.

When trying to line up the input shaft splines with the clutch hub splines, shift the tranny into any gear and rotate the output shaft with a pair of pliers (place rags over the splines first). This will spin the input shaft so the splines will align. Then all you have to do is align the bell housing so it is parallel to the back of the engine block so you can slide the input shaft into the clutch hub. If the bell housing is not perfectly parallel to the back of the block, then you will not be able to slide the tranny into place even if the splines are perfectly aligned. Once everything is aligned the tranny will pop into place with almost no effort. For more tips on making tranny instillation easier if you do not have an engine hoist, please refer to . I highly recommend that you read the tranny install page if you have not done so yet.

Contact and reference info[edit]

For the most up to date info on parts please see the first post of the thread linked bellow.

Maximal Performance

Supplies 5 and 6 speed TC braces and front LSDs.

Ray Pampena Motorsports

Makes and installs the 5 and 6 speed reinforement rings. They rebuild trannys and TCs.

Nelson Performance Pro

Supplies 5 speed TC braces.


Supplies rebuilds, used and some new parts, torsen front LSD, as well as 6 speed JMD gears. They rebuild trannys and TCs.

Kormex on 3Si


Speed Freak Racing

Contact them for the LSD insert.

Applied Industries

Locate a dealer near you using this link.

All of our roller bearings can be found at Applied Industrial Technologies. They will be able to get the roller bearings in the transaxles and TCs so long as you have a number off of the race for them. The only exception is the bell housing side input shaft bearing. These have proven to be very difficult to locate. Find a dealer near you. They were much cheaper than most vendors and are an authorized distributor for Timken and Torrington bearings. Here are the numbers for the roller bearings. All are the same for both 5 speeds (440) and 6 speeds (446) except for the counter shaft bearing on the end cover side.

Bell housing side / End cover side

Input shaft 308-410 / 57497

Counter shaft 30209 / 30207(440) or 30208(446)

Center diff 32010 / 32009

Pinion shaft 32009 / 32009

Front diff 32008 / 32009

Mark Williams Enterprises

18/25 spline 300m output shafts and 25 spline 300m TC spools

Contact Travis @ MW enterprises 800-525-1963

EK2 Manufacturing

5 speed TC cage

PM Bob, his user name is ek2mfg.

Super Car Engineering

Billet 6 speed 1/2 and 3/4 shift forks, front, center, and rear LSDs. New and used parts available.

LSE Performance

They carry the cast stainless steel TC housings.


North Bend Tech

NBT produces the 25 spline quadco XR steel output shafts and TC spools with anti-rust/corrosion coating on the splines.

PM DarkHelmet for possible rebuild services and/or parts.

PO Machine

Contact John Redgate for 6 speed bell housing reinforcement.


3SX Performance

Carries new and used trany parts, used TC parts, all of the SS housings, and 300m shafts and spools.

Contact the service department for tranny and TC rebuilds as well as used tranny and TC parts.


Contact the parts department for new tranny parts.


Stealth 316 by Jeff Lucius

Great source for learning more about your 3S.

Don't forget about your fellow 3/S members. Many of us have a lot of experience with these cars. I will leave it up to the members to speak up about doing any work on the side. But this thread isn't for finding work. It is for providing info. However, if you would like a recommendation on some one or a shop to do the work, feel free to PM me.

If you have experienced a drive train failure or have some other useful information, then I encourage you make a post on the forums. Or if you know of any one please ask them to post their experiences (hopefully with pics) on the forums. The members of 3Si are always interested in knowing who is breaking what and under which conditions.