My buddy is using a 42r and has a stage 4 shep trans with an act 2900 and his trans is holding up fine; but interesting info nonetheless.

 

That clutch holds that kinda power? The ACT 2900 doesnt' beat up the trans?

 

There's a similar thread to this somewhere. What I basically got out of it was that the OP there thinks that only so much can be done with the stock components, that we aren't really getting "built" transmissions from places like TRE, Shep and Jack, just meticuously assembled stock ones. The weak stock gears are still there. You have to get a dogbox if you want something that's stronger, or just rebuild your transmission constantly.

 

There are different gearsets that can be used, some are stronger than others, but helical gears themselves are not that great.

If you want something that's going to hold up doxbox is the only way to go. That being said I have had no problems with my High-end build by Jack M.

 

There are different gearsets that can be used, some are stronger than others, but helical gears themselves are not that great.

Right, by stock I meant anything from Mitsubishi wether it be DSM or Evo3 gears. Even if the Evo3's are a little stronger, they still probably weren't engineered with the idea of 500+ ft/lb highway pulls in mind.

 

Agreed, 500+hp and you are in a World where you can break gears. The only gears I have personally broke in my cars were GVR4 1st gears. I have never broken any of the others. I can shift quickly but am smooth and gentle with my shifting and clutch engagement. I think not shock loading the system is key to long trans life out of a high powered car. Many that I see break 2nd-4th shock load their cars terribly and it really just makes them slower doing it that anyway, IMO. My brother has a few cars in the 500-700hp range and all we do for him is weld the center diff and tighten the preloads and they live forever as he has also learned how to not shock the system. You would be surprised how much power a 90-92 trans with a welded center can take before it lets go.

I also believe fluid is key. If you are using BG or Synchromesh garbage your gears and bearings will wear and break faster.

Jack

 

I remeber you telling me this before. You said running slicks actually helped those cars as spinning tires shock loads the gears. Does the technique used with shifting matter for gear teeth holding up? And your specifically saying 500 hp and up is were the damage is, but I was always told to go by the torque number not the hp. I hear the torque is what to look for, and I was told 400 ft/lbs is as far as you'd want to go "safely" and you enter a gray area with anything over that. ( Meaning anything can happen.)

Jack I think you do a awesome job on dsm trannys, and I know your only limited to your experience and the experience around you, which is good, Im also looking for other tranny builders and regular joes with regular trannys making these high numbers to chime in on their experiences also. Just trying to gather as many opinions and info as possible, as it will be useful to a lot of people.

As far as fluid Ive read that EVO Mr fluid on that one thread was good.
I was looking forward to trying that despite cost if its really cracked up how they say it is.

 

Jack what Fluid do you recommend?

 

I ran a stock 156K mile 90 GST transmission to 11.80 at 126mph. I had been racing it for 5 years prior to that at lower power levels. The last 2.5 years of that transmissions life were 120+ mph passes. I did about 50-60 passes a year back then. Never broke it.

I am now running a shep stage 2 fwd in my 90' that was rebuilt from a 92 core. It shifts better and again has not failed since I put it in late spring of 2006. It has seen probably 100-120+ passes and 15,000 miles of street driving. Much of the street driving includes many dyno pulls and many street tuning pulls. So once again lots of load on third and 4th gear. The car goes 130 in the quarter but unfortunately spins on the dyno but torque is extremely high considering it has stock cams and sees 36psi boost spikes. I've gotten my life out of this transmission and it should have probably failed a year ago, its just seen too much abuse. I'll run it till it breaks and then give john a 92 AWD core to rebuild.

My friend has similliar success with a stock 90 awd trans and same luck with shep rebuilding that trans. He has gone as fast as 11.80 at 122mph in a damm near full weight car.

I think driving is key. I also think that fluids are also key. We utilize shockproof with a little synchromesh, just enough to be able to shift well.

 

Keep in mind your FWD , and I think there is less stress on your transmission than a AWD. But good to hear of your success, and nice times. Was that on slicks or drag radials?

Does anyone feel that vehicle weight ( in regards to weight reduction ) helps prolong transmission life?

I felt it should help some with most of the drivetrain parts, but I didnt think it would have a significant affect on gear life since the initial torque hit on the engine to the gear is the same regardless of vehicle weight. I dont know.

Also Im running shockproof blue in the tranny right now, I used to run syncromesh, I wont run it anymore though, its too thin, I think the MT90 is too thin also. Royal purple was good i hear.
The shockproof definitely would help deal with the torque, but the reason Im not going to run it again in the tranny ( only tcase/rear diff) is because I hear the shock proof friction modifyers or whatevers in that fluid is thick and can cause clogging and blockages of flow to certain components in the tranny.

Ultimately my end goal for my car is mid 400awhp with torque around the 400ft/lbs area, on a 2800lb awd car w/ driver and cage, plus tires good enough for 1.6 60fts with the welded diff. Assuming that would make a high 10 sec car with high 120mph traps which is plenty, and just at the limit before constant drivetrain worries.

 

Keep in mind your FWD , and I think there is less stress on your transmission than a AWD.

I understand in drag racing an AWD trans would see more stress then a FWD even with slicks while launching, but the OP mentioned highway pulls in 3rd and 4th causing failures. Would an AWD trans still take more punishment in those conditions, or would it be about the same?

 

Not to hijack this thread, but are you not recommending syncromesh? I was under the assumption that it was good for our trannys...I'm no expert, but that's just what I had gathered from the forum.

 

I used to run it because I figured I could shift much better with it, but turns out when I put in the thick ass shockproof in the trans the shifting really didnt change much after the fluid was warmed up. It was a little difficult when it was cold though with the thicker fluids.
I think a lot of people up north like to use the thin fluids since it gets so cold, but honestly in the summer I think the syncromesh is too thin, and you WILL be changing it more often. I mean as often as every 4-5k because it breaks down quickly. Id only recommend syncromesh on dsms that have really old notchy syncros with light mods, (stockish) and/or not making more than 300whp. Get a 2nd opinion though.

I understand in drag racing an AWD trans would see more stress then a FWD even with slicks while launching, but the OP mentioned highway pulls in 3rd and 4th causing failures. Would an AWD trans still take more punishment in those conditions, or would it be about the same?

Right, I was just saying because he was telling us about all his good luck with consistent fast track times without breaking. I know the gearing is different from awd to fwd, I dont know if the gear size or strength is any different.
That would be interesting to know. The main concern with the 3rd and 4th gears being weak in our transmissions is because of the physical size. 1st and 2nd gear doesnt seem to have the same problems, and I dont think 5th gear is used enough in any type of racing situation to develop a issue.

I still think that even the gears of the awd are under more stress than the gears in the fwd. When I opened a transmission not too long ago I remember noticing that either our 3rd or 4th gear teeth are also connected to the main gear teeth of the center diff, so when your driving its always turning that. In addition the AWD tranny has more drag due to the other drivetrain components ( tcase, rear end etc.)
This is just my speculation, someone else might want to jump in.

During my build, all I think I will necessarily need to do for my transmission is install a new oem 3rd and 4th gear, with new syncros, and maybe the hub and slider stuff too depending on condition. My 3rd gear is badly beaten up, it grinds if its not shifted a certain way, and the gear is surely fatigued from xxxx number of miles on it. Having fresh gears is key in making it hold up to high numbers of torque. Ive thought about cryotreating but I was told that it might not be worth the effort or money for what Im trying to do, and it usually wont save you if you over power the gear teeth.
The guys making a lot of power around here have told me that every time they do a high powered pull on those gears , that every pull is like a number, and you can only do it so many times before it fails. That must suck to have that in the back of your head every time you go to have fun with your car ...

 

Jack also warned me before about using the NLTS, and it has to be done a certain way.

I used to NLTS all the time when doing pulls because it actually felt smoother to shift like that, and I got it into the next gear quicker and easier, not to mention the fact that I didnt blow off any of my boost.

I will use it less now, once I start making the kind of power to worry about causing damage. I also hear you can shock load gears pretty badly when your making enough power to spin the tires on rolling pulls in a awd.

 

I dont have a lot of experience whit high power dsm,but im sure about one thing,a power shift whit NLTS is the best way to destroy your trans.

Last summer i just got my new chip, then i discover how fun it was to get in third gears in full boost (NLTS) and smoke those street tire until the end of the third...For sure it was fun but it dont last long,after barely 10 time i got no more third gear.

All this only on evo3 16g @19psi whit syock trans an 225/45/18 steet tire

 

What fluid were you running, what yr trans and how many miles.

In your case I dont think that is soley what messed your 3rd gear up.
Ive ran more psi with probably more mods than you have on my e316g setup while NLTS'ing all the time in every gear when Im on it and never experienced any issues or damage, and this transmission has seen many abusive passes and freeway runs.

Im not saying it isnt bad as I mentioned earlier, but I dont think you nor I are at the power level to worry about it with everything else in proper working order/condition. Your gear must've already been on its way out.

 

Meh, I just blew mine apart two weeks ago. Running at 19 psi, and speed shifting into 2nd and 3rd, tore apart everything. Apparently, badly adjusted clutches can cause gear bind, since they keep the transmission under load during shifting. I'm pretty sure, aftermarket clutches without proper adjusting kills more transmissions than just about anything else.

 

Word... All these worn pedals, and all these stiff clutches, mixed with everyone and their cousin doin tranny rebuilds.... Nothing like wiping out a fresh set of syncs, with the first test drive...

 

Anyone else with high H.P. that would like to jump in and share their experiences?

 

I mentioned earlier about my friends 42r and regarding that i think the right clutch definitely plays a part in transmission life his twin disk tore up his transmission TWICE! But after he went back to the act 2900 he's had no problems

 

The biggest problem I find is the lack of extra trannies when yours blows.

 

Or the lack of money^

The setups that I think are eating up gears and drivetrain parts easier are the medium sized turbo'd fast spooling ones with mild cams and maybe no intake mani upgrade, thus they are making most of the peak power in the lower rpms ( i.e. stroker, or nitrous fed setup) I used to be one who wanted a hard hitting torquey setup but now days I am aiming my setup for a more higher rpm, laggy, less peak torque type of setup. The only thing that sucks about high rpm is more motor stress, and hard to shift.

If what I heard is true that the HP doesnt really matter so much, and its all about the torque then hell that would mean you can make 650awhp with 400 ft/lbs of torque safer than say a setup that was making 500 awhp and 500 ft/lbs of torque? Flow-Bro, perhaps why your friends huge laggy 42r setup hasnt butt fucked the tranny yet?

I do plan to throw a jmf drag mani and hx40 on the car after the motor is built, I know the holsets spool fast, but I think that setup max out on pump gas will be fast enough for my goals and vehicle weight, and yet still able to be made reliable.

 

Flow-Bro, perhaps why your friends huge laggy 42r setup hasnt butt fucked the tranny yet?

I forgot to mention he tore up his trannies on a 35r

 

Well what about the fluid? I had been running aprox 2 quarts of syncromesh with 1 quart of mobil 1 and changing it every 20,000 miles. (Stock trans)
Should I be doing something diffrent?

 

Well what about the fluid? I had been running aprox 2 quarts of syncromesh with 1 quart of mobil 1 and changing it every 20,000 miles. (Stock trans)
Should I be doing something diffrent?

I don't care if you don't like them, nobody knows more about the dsm trans than TRE

http://teamrip.com/manual_transmission_gear_oil_recommendation_info.html

 

Some people say mixing is ok, and others wouldnt advise doing that.
I think your def at the power level that you should avoid syncromesh at all, especially if your dragging it out 20k. Thats a lot of miles. I dont have any experience with the Mobil 1.

 

The big thing that we sometimes forget to think about, is the condition of the stock trannies when we start beating on them. The tranny that I just blew apart had 100k miles on it, on a T25, then I throw it in a car with 200 more HP, and it lasts 15 drag passes. If it was, say, a brand new stock replacement, I might have gotten the same 15 out of it, or I could have gotten 100, who knows. What we need to do, is get a freshly rebuilt stock tranny, put 400 ft/lbs on it, and constantly drag it till it breaks, rinse and repeat, until we get an average number of passes per transmission.

 

Rinse and repeat lol ^ I wish it was that easy.

Though you can only abuse the tranny so many times, even on a low powered car, I wish you shouldnt have to start counting your passes until you get into some serious power. ( 500-550 ft/lbs+)
Ive always considered the input shafts weak on these cars. Even just looking at its physical size and thickness compared to that of say a Camaro's input shaft you can see its weak.

Something else I was recently talking about with my friend Drew at Darkside performance, he is utilizing a nice transmission fluid cooler setup that he is customizing into his and another dsm'er's tranny, and he believe this will allow it to last much longer.
He said he's spoken with a tech at shep's and they were telling him another reason why the trannies fail quickly on high powered cars is because the fluid breaks down after a matter of pulls, and then there is hardly any protection on the gears.
He was saying if you have a fluid temp gauge on the tranny you would see that one pass makes the tranny temp sky rocket, so hot lapping is really bad for it.
There are a lot of car circles that have been doing tranny coolers for this exact reason, especially road race and drift cars. I believe there is definitely some truth behind it. Whenever he's done setting it up on his tranny I will try to get permission from him to post pics of it. He is going to be using it on his fully built 1g awd, with HP goal of 700.

 

Interesting info B.B. thanks for sharing, I'll change my fluid every other trip to the track, about twice a month. We'll see how long it holds. I have aprox 10 passes on it now, no for than 12 1/4 pulls on her.

 

In between those drag passes, I'm pretty sure I've changed the fluid in my tranny/tcase about... 4 times? I put the tranny in, around October, dropped it the next day, since I blew the clutch apart that night during tuning. Dropped it again, about a month later when I found a ripped seal in the right side output shaft, and I changed it about a month ago, when I did my "Hey, this thing has been sitting for a month or two, so I should make sure it holds together" Check.

 

Yea I saw that before, good shit ^

 

Thanks for the link loki, I knew gl4 was the only way to roll, I'm going to have to track down some shockproof and give that a try. My trans right as of now is 100% so I don't need syncromesh in order for it not to grind.

My tre rant is for another thread.

 

http://www.dsmtalk.com/forums/showthread.php?t=207430

 

WOW. My case cracked as well but nowhere near like that!

 

Well, speaking from experience, I had the best results with the DSM AWD transmission up to 350-400whp/350tq before anything past that would find a way to fail. My last setup put down 766AWHP/~700TQ at all 4 wheels. The new setup is going to be around 900AWHP (that is the goal) conservatively on the S374R. I am still expecting near 650-725TQ at the wheels.

I am now on my 16th transmission (15 of them being a wide range of fully built transmissions over the years 2003-2008). I have been building them now for the last 2 years with good learning experiences.

There are several weaknesses in the DSM transmission; the main ones are the following:
*Gear face size, shaft size, etc.
*Center differential
*3rd/4th gearset and 3/4 hub and slider assembly (late 91-early 92 is the best).
*Input shaft and 1st gear.

With these flaws in mind, the first thing would be to run a straight-cut dogbox gearset to take care of the gears. The next is to run a welded center diff, a spool, or a 4-post Chromoly 4-spider gear center differential (NOT a machined down cross shaft -- there is also the necessity for better oiling to the spider gears, so oiling grooves in the chromoly cross shaft is key). If you are going to be banging gears (with a dogbox), then the chromoly shift forks should be used, but if you are running a helical transmission, it is in your best interests to properly, softly shift the gears using the aluminum shift forks as they will put less wear on the hub and sliders.

If you are on a real-world budget, then the most important things would be to use a new Input shaft (and corresponding 1st gear), Intermediate shaft, and 3rd/4th gear assembly. All of these parts should be deburred and detailed to remove all rough/sharp edges. As well, surface treatments such as cryo-treatment (helps with having more structurally uniform material and surfaces along wih deburring/detailing a gearset), REM polishing (reduces friction and stress on a deburred shaft/gearset), and shot-peening (helps with strength and oiling surface adhesion) are all useful treatments to help increase longevity, reduce wear, and increase oiling surface adhesion/lubrication.

A quality center differential should be used -- a well-built 4-spider center diff with an upgraded cross shaft and a machined cover with Torrington bearing modification can handle quite a bit of abuse and live. I have had machined stock cross-shafts, BM transmission cross-shafts, Speed-design cross-shafts, and Beyond Redline Chromoly cross-shafts in my transmissions over the years. The best one for my power levels that has survived with minimal wear characteristics has been the Beyond Redline hardened chromoly cross-shaft with machined oiling grooves. This one has lasted the last 6 transmissions and looks great everytime I inspect it -- I have not broken one of these to this day, whereas I have shattered the other ones tested over the years.

The late 91-early 92 3rd/4th gears and hub/slider assembly is the strongest OEM part for our transmissions, along with its corresponding 3/4 shift fork and 3/4 shift rail (having it milled to accept a second roll pin to properly hold the 3/4 shift fork better and preventing it from snapping off its lower mounting point under hard shifting). If you are using a late 92-1999 3rd/4th gearset, you WILL eventually shatter your 3rd/4th hub/slider assembly either through imploding the hub, or shattering the slider -- they are just too thin and weak to handle anything over 350tq reliably. Sure, it may have better/bigger synchros, but it is extremely fragile. The late 91-early 92 conversion is the way to go -- it is also the same hub and slider that is used with the Evo 3 3rd and 4th gearset, along with taking the same springs and keys for the hub/slider assembly. Jon at TRE does use better spring steel for the hub/slider springs that helps in preventing the springs from failing, and are worth the additional cost as the springs are necessary parts. Also, the Evo 3 3rd/4th gears do come heat-treated (like all the mitsu gears) AND shot-peened from the factory. The Evo 3 1st gear/input shaft is NOT shot-peened from the factory, so it is a good option to add, including deburring/detailing. I also like to use REM or cryotreatment on the 3rd/4th hub and slider as this part can see a heck of alot of heat and load on a high-power car. I still regularly burn out a 3/4 hub and slider on the dyno, resulting in destroying the slider and the 3/4 shift fork == it will get overheated and cause shifting problems. Oiling is key, so the less friction, and the more oiling adhesion is extremely important for this key part. The 3rd and 4th gears also are small, and have a tendency of shearing all the teeth off past 450+TQ; The last one that I exploded lasted the longest with cryo-treatment and deburring/detailing of the gears and the intermediate shaft, but still exploded around 700TQ at the wheels on the dyno.

Next, the 1991-1999 intermediate shaft does have better oiling passages than the 1990-early 1991 shaft. Just know that it is not directly interchangable with 1990 shafts in the 1990 transmissions, as it uses a different gear pitch and gear tooth root thickness. You must use a corresponding input shaft and gears (91-99 DSM OR Evo 3 parts are interchangable with the corresponding hub/slider/rail/fork assembly). The intermediate shaft is still weak, though it may be the beefiest shaft in your transmission, it has a very small gearface for the 3rd and 4th gears, so it is imperative that you properly debur/detail the shaft, and use some sort of beneficial surface hardening/treatment. It is very common to shear the teeth off the 3rd gear face of the intermediate shaft, as it sees all the load, all of the time, since it shares the drive force with the center differential/output shaft/etc. I have had the best luck with deburring/detailing and cryo-treatment in conjunction, but I am going to try shot-peening on the next one as it will help in keeping a bit more oiling adhesion on the shaft. If you are making serious torque numbers, this should be a required replacement part when doing a transmission buildup.

The input shaft is strong enough for most setups -- EXCEPT when running a GVR4 input shaft/1st gear -- I have popped these with less than 400whp/360tq, shearing the 1st gear teeth to oblivion. If you want a taller-than-stock 1st gear, go with an Evo 3 1st gear and input shaft. It is also imperative that you keep an eye on the shaft for runout (making sure that the shaft is not bent), and that the shaft splines are perfectly straight with NO wear (if possible, use no grease on the shaft splines for the clutch; it will only cause a wear surface; use only a tiny, tiny bit of synthetic high-temp grease on the splines of the clutch disk if you are using a single-disk setup; use NONE if you are running a multi-disk clutch). I have bent input shafts around 600+whp, and I have twisted the splines completely on my input shaft with my last twin-disk at 700TQ at the wheels (it also sheared the splines off of both my QM clutch disks). Shot-peening and cryo-treatment for the input shaft is definitely beneficial.

One of the most important things for these transmissions is properly shimming the gearshafts (center diff, output shaft, input shaft, intermediate shaft and front differential. With the front diff, follow the specs since they are standard roller bearings, it doesn't need preload. I usually have the output shaft at specs for preload, and slightly more on the center diff than spec, and then more preload than stock on the input shaft and intermediate shaft. From the forces going on inside your transmission under load, it makes your input shaft and intermediate shaft want to thrust away from each other. As well, once the transmission heats up, the aluminum case will expand. So, this is the reason for increased preloads on the two main shafts, so that it will keep its preload under high temperatures and high load without allowing the shafts to separate. This is usually the key reason for gear failure.

Personally, if you are intending on making crazy torque, you better know how to make your vehicle respond smoothly -- slicks, good center diff, twin-disk clutch, good motor mounts and axles, along with utilizing a hand brake or e-brake to properly pre-load the vehicle to launch it without causing shockloads on the transmission. I also use Redline Lightweight Shockproof in my transmission, and regularly flush it (or fully disassemble the transmission regularly for rebuilding/refreshing/cleaning oiling passages, etc.).

Finally, if you want a transmission that is going to last, then you are either going to have to pony up for an IPT race transmission, or a race-transmission. At extremely high power levels, I would only recommend a dogbox or an IPT automatic.

See, I am crazy for the fact that I still run a 5-speed helical transmission with modifications at my power levels. They will not last long -- it is just a matter of design. They were only designed to handle around 200-400TQ before failing based on which parts you use. Anything past that level, you are playing with a hand grenade that doesn't have a safety pin in it. It WILL fail sooner or later. Your driving characteristics and power levels will be the deciding factors in how long it lives before it dies.

If you don't like what I have to say about transmissions, or my experiences, fine. Go and buy a Supra or a T56 transmission car with a Viper output shaft. Both of these transmissions are beefy and can handle nearly everything you want to throw at it without failing. If you cannot afford to be replacing/rebuilding transmissions regularly, then I would suggest staying under 400whp/400tq. Your driveline will like you a whole lot more!