Stock or built transmission

[Talipse96]

I have already read through a lot of transmission threads and they all pretty much cover the same thing over and over. I don't need any references to shops that you think are better. I might be contacting some to see what they say.

This is where I'm at right now. I want to make 400awhp or at least close to that with my Talon. I have a stock trans (5spd) right now with the syncros going out. I would like to re-build it so that it can handle the power that I want to run. I would be making a few sprinted runs down the track and some daily duties.

I know that the stock trans can hold that power as long as I don't beat the crap out of it, so please give me reasons why I should upgrade beyond stock.

For those of you making some good power on your stock trans, how have you made it last?

 

[woodnbronze24]

It really depends on if you have a back up vehicle in my opinion. A shep or tre trans will hold that power and give you peace of mind.

Also, you'll find the price difference between a local shop to do a rebuild vs a shep or tre build is quite small. I'd trust a Dsm trans specialist over a local shop any day.

 

[Talipse96]

It really depends on if you have a back up vehicle in my opinion. A shep or tre trans will hold that power and give you peace of mind.

Also, you'll find the price difference between a local shop to do a rebuild vs a shep or tre build is quite small. I'd trust a Dsm trans specialist over a local shop any day.

I have other vehicles that I can drive. I have no problem with "down time".

The issue I have with local shops is that I don't think I will get the quality out of them as I would with the DSM specific shop. I wouldn't have an issue with going with a local shop if all I would need to do is replace my syncros.

I use to want the stage 3 trans from shep. Then as I read that people made some pretty good power on a lighter built or stock trans.

I would just like to hear experiances from people with stock transmissions. How well do they hold up under moderate power?

 

[eclipsh]

Having spent some time talking to John at TRE about this very issue before I did my rebuild I'll pass on what he told me.

Every time you stress the gears in your transmission you're taking away from the life cycle of the gears. The harder you stress them the more you're taking away. He suggested shot peening my gears to extend that life cycle for minimal additional cost. It also raises the critical stress values much higher so you're much less likely to strip teeth off at your target power level.

If you haven't read his FAQ section you should. This one goes into lots of detail about what shot peening does:

SHOT PEENING INFO

I didn't get my gears detailed but if you have the extra here is what that does:

GEAR DETAIL INFO

The gist of if was that I probably could have run a stock rebuild but I'd be replacing the transmission
sooner. By doing that service it gave me peace of mind knowing that the extra couple hundred bucks was giving me a much longer service life.

For the nerds like me, here is some more good info on the process:

http://abrasivefinishingcompany.com/t-shot-peening.html

 

[raped]

In my opinion don't waste your money. Replace the worn parts, shim the trans tight (this makes the biggest difference), and be done with it. A trans with stock internals is just that....a stock trans. All of these gear treatments aren't worth the cash and only make you feel better. As far as being worried about fatigue of the gear...replace your intermediate shaft but at your power level I don't think its necessary. The only true "built trans" is a dog box.

Good luck

 

[eclipsh]

In my opinion don't waste your money. Replace the worn parts, shim the trans tight (this makes the biggest difference), and be done with it. A trans with stock internals is just that....a stock trans. All of these gear treatments aren't worth the cash and only make you feel better. As far as being worried about fatigue of the gear...replace your intermediate shaft but at your power level I don't think its necessary. The only true "built trans" is a dog box.

Good luck

You are entitled to your opinion but what knowledge is that opinion based on? What is your experience?

Improving the gears means they are no longer "stock." Shot peening is used for all sorts of industrial applications and is proven technology. So is removing stress risers. Jon has proof of the benefits from all the transmissions he has built using these methods. I've studied the materials science behind this and can tell you there are benefits.

 

[donniekak]

Shot peening does help, and is cheap enough to not really be an issue. The single most important thing you can do to make the transmission lees prone to catastrophic failure is welding the center diff. The next in line would be a stronger 3-4 hub/slider/gear, for any trans made after 92.5. After these weaknesses have been corrected, a hardening process like peening is a good idea. Now you have a solid gearbox to start making mods to correct the poor high rpm shifting issues. Double synchro 2nd, 3rd, and 4th, is a good idea for a drag trans. It's also advisable to shim the trans anywhere from 2-4x stock preload when assembled. After all this "stage 4" madness what do you have, a polished turd that is going to break anyway. The last incurable problem of any stock gear based dsm trans is the small physical size of the gears. The only way to prevent the eventual shearing off of the gear teeth is a straight cut gearset.

 

[raped]

You are entitled to your opinion but what knowledge is that opinion based on? What is your experience?

Improving the gears means they are no longer "stock." Shot peening is used for all sorts of industrial applications and is proven technology. So is removing stress risers. Jon has proof of the benefits from all the transmissions he has built using these methods. I've studied the materials science behind this and can tell you there are benefits.

I have rebuilt countless DSM transmissions for cars making stock power all the way to 900 whp. I have used gearsets that have been shotpeened, REMed and all other treatments from other shops, they are all going to break anyway if you make enough power. I just think that the whole "built transmission" thing is overhyped. You are welcome to spend your money on whatever you want I just think its better spent elsewhere.

I do recommend welding the diff, and I also like the evo 3 double synchro gearset. Most cars don't need the double synchro gearset but it will help you to shift at higher RPM with a single disk clutch (twin disk guys shouldn't have any problem shifting at higher RPMs with stock single synchros)

 

[eclipsh]

I have used gearsets that have been shotpeened, REMed and all other treatments from other shops, they are all going to break anyway if you make enough power.

I think your logic is a little flawed there. It is like saying you could rebuild your engine with forged pistons and rods but why bother because they're going to break if you make enough power anyway. At 400 WHP you are pushing the limits of the stock transmission. If he's already paying to have the transmission gone through it makes economic sense to pay a little extra to add strength and longevity so he doesn't have to repeat the process after he breaks his stock unit.

Also, unless this is a dedicated drag race or rally car I am not a fan of welded center differentials. If you're planning on going around turns without slipping wheels you're going to have binding issues. Ever done a tight turn in a 4wd truck on dry pavement with it in 4wd? The tires are forced to slip instead of the center differential since they have a non-slip center (like a welded unit). It makes the tires chirp and pop and sends stress back through your drive train. Mitsubishi put the LSD center in for that exact reason. A 4-spider conversion is much better for anything street driven or taken to tracks with turns in them.

 

[donniekak]

I think your logic is a little flawed there. It is like saying you could rebuild your engine with forged pistons and rods but why bother because they're going to break if you make enough power anyway. At 400 WHP you are pushing the limits of the stock transmission. If he's already paying to have the transmission gone through it makes economic sense to pay a little extra to add strength and longevity so he doesn't have to repeat the process after he breaks his stock unit.

Also, unless this is a dedicated drag race or rally car I am not a fan of welded center differentials. If you're planning on going around turns without slipping wheels you're going to have binding issues. Ever done a tight turn in a 4wd truck on dry pavement with it in 4wd? The tires are forced to slip instead of the center differential since they have a non-slip center (like a welded unit). It makes the tires chirp and pop and sends stress back through your drive train. Mitsubishi put the LSD center in for that exact reason. A 4-spider conversion is much better for anything street driven or taken to tracks with turns in them.

You missed what he's saying. Unless you have a ppg gearset, your "built" transmission is still stock mitsubishi gears. While i do differ on peening the gears, he is dead on about spending thousands on something that lasts a small fraction longer than something that only costs a few hundred bucks. Here is why you weld the diff.
This is a non welded
<iframe title="YouTube video player" width="480" height="390" src="http://www.youtube.com/embed/DBjDyKeL_dI" frameborder="0" allowfullscreen></iframe>


Here is a welded diff launch.
<iframe title="YouTube video player" width="480" height="390" src="http://www.youtube.com/embed/XKgml8rHIvs" frameborder="0" allowfullscreen></iframe>


The shifting of power rear, to front, and back and forth destroys drivetrain parts. A welded diff gives a much smoother launch. For all the people worried about streetability in a 500+ horsepower, 2.0 liter, 20 year old car, good luck.

 

[Calan]

Interesting. I've never seen a slow motion video that showed that so clearly.

Do you still see that back and forth power transfer with a 4-spider diff?

 

[donniekak]

Do you still see that back and forth power transfer with a 4-spider diff?

Yes. The only difference is the diff itself is stronger. It still behaves in the same manner.

I really notice the effects when running a 3 bolt rear. With an unwelded diff, i break rear axles much more frequently than with a welded diff.

 

[twicks69]

I have already read through a lot of transmission threads and they all pretty much cover the same thing over and over. I don't need any references to shops that you think are better. I might be contacting some to see what they say.

This is where I'm at right now. I want to make 400awhp or at least close to that with my Talon. I have a stock trans (5spd) right now with the syncros going out. I would like to re-build it so that it can handle the power that I want to run. I would be making a few sprinted runs down the track and some daily duties.

I know that the stock trans can hold that power as long as I don't beat the crap out of it, so please give me reasons why I should upgrade beyond stock.

For those of you making some good power on your stock trans, how have you made it last?

The weakest parts in your 95-99 transmission (torque capacity wise) are the 3rd/4th hub and slider assembly and the stock center differential.

The 3rd/4th hub and slider assembly likes to either implode the hub or explode the slider after ~400TQ. It is only a matter of time if you do any sort of load in 3rd or 4th with this kind of torque. The fix to this is to use the late 91-early 92 3rd/4th gearset conversion which utilizes a late 91-early 92 3rd gear, 4th gear, hub and slider/keys/springs, shift fork and shift rail/rail end. You can always swap out the following parts for Evo 1/2/3 parts: 3rd gear, 4th gear, 3/4 shift fork, and 3/4 shift rail/rail end.

The Evo 1/2 OEM transmissions utilized single synchro versions of the Evo 3 3rd/4th gears that had the same gear ratio. The Evo 1/2/3 had a mixture of shift forks utilized from the factory including solid steel ones without shift pads, with plastic shift pads of varying sizes. The best ones were the Evo 1 solid steel shift forks, but they are non-existent unless you find an Evo 1 used transmission. The 1990-early 1992 transmissions used an aluminum version of this 3rd/4th shift fork design for wear life, at the cost of breaking under very hard shifting. The Evo 1/2 also used forged shift rail ends on all 1/2, 3/4 and 5/Rev shift rails and had to be used as a matched set with the Evo 1/2/3 shift selector or you needed to clearance the shift selector and rail ends to work properly. The Evo 1/2/3 shift rail ends worked best with late 1991-1999 shift selectors and still sometimes require a bit of clearance work to function properly. The late 1991-early 1992 3rd/4th shift rail had a heat-treated rail end that was stronger in design than the 1990-mid 1991 but is not interchangable unless you do a shift selector conversion and complete shift rail conversion with other parts involved. The late 1991-early 1992 and Evo 1/2/3 3rd/4th shift rail can be used in late 1991-1999 transmissions when used with a matching gearset from an Evo 1/2/3 or late 1991-early 1992 DSM.

The 1990-early 1992 DSM and Evo 1/2 utilize the same diameter 3rd/4th synchros and hub/slider assembly whereas the mid 1992-1999 used a larger diameter synchro with a substantially thinner and inherently weaker design hub and slider assembly. The Evo 3 used a very thick slider and the same hub as the Evo 1/2 and early DSM stuff and had a bit more clearance for oiling to the 4th gear synchro as the Evo 3 double synchro 3rd/4th assembly needed a bit more space to get proper oiling. You can use an Evo 3 3rd/4th double synchro gearset with a late 1991-early 1992 3rd/4th hub and slider but you will need to have the 4th gear and 3rd/4th hub machined for additional clearance and oiling, otherwise you will end up with a torched 4th gear synchro almost immediately due to lack of oiling.

The Evo 1/2/3 3rd/4th gears are "stronger" than the late 1991-early 1992 DSM gears only on the fact that they have a lower tooth count and more meat on the root radius of the gear teeth. The gear tooth angle is still the same as the late 1991-early 1992 DSM gears.

The center differential is the other weak link in all DSM's and Evo 1/2/3 at around the same power levels as the 3rd/4th hub and slider before the two spider gears either explode or the cross-shaft shatters. Common wear items that should be replaced are the spider gear shims, the lower pinion gear brass shim and the upper pinion gear oiling washer. The upper pinion gear oiling washer has a tendency of wearing out and then microwelding itself to the upper pinion gear and center diff cover causing catastrophic failure to the differential or at least the upper pinion gear and center diff cover. If the wear is excessive it will also place the spider gears and lower pinion gears into risk of failure from excessive gear lash, resulting in spider gear washer failure (and case damage) or splitting the lower pinion gear brass oiling shim. If the pinion gearset gets damaged in any way, you need to replace the entire pinion gearset as they are not available as separate pieces from Mitsubishi. I would recommend having the center differential serviced and upgraded to a minimum of a Torrington bearing upgrade for the upper pinion gear by having the center diff cover machined for the additional clearance required to run a Torrington bearing and oiling shim, and replace the spider gear washers and lower pinion gear brass oiling shim as a longevity upgrade. The 2-spider diff can only hold so much power and abuse before it fails, so upgrading to a 4-spider center diff is a must if you want to keep streetability while having increased torque capacity. Most vendors just machine down the stock crappy cross-shaft to incorporate 4 spider gears while TRE and myself have designs that utilize a better material custom machined 4-spider cross shaft that will be able to capacitate substantially more power without failure. To do the modification for a 4-spider center differential upgrade, you will need an additional pinion gearset (two more spider gears required), a 4-spider cross-shaft and a machined center differential housing to fit the 4 spider gears. The benefit to a 4-spider center differential is the ability to not sacrifice streetability while increasing torque capacity without failure. The benefit of a welded center differential is taking the spider gears and stock cross-shaft out of the equation and having a beefy "locked" differential at the sacrifice of streetability as the welded differential will bind the front/rear wheels during turning or unequal wheel speed causing substantially more wear on your other drivetrain parts.

A blown or damaged center diff and a welded center diff will put alot more wear on the output shaft splines and transfer case input sleeve splines causing premature failure of the parts. A blown or damaged center diff will also burn out your viscous coupler.

Other common wear items that should be replaced are the input shaft and intermediate shaft tapered roller bearings, 1/2 and 3/4 shift forks, 1/2 and 3/4 hub and slider assemblies, and synchros. 1st and 2nd gears also get worn out over time the most as they are the most-used gears for street cars. The dog engagement teeth for the synchros to engage with the associated slider will cause gear popout or grinding while engaging the gear; it is not just as simple as a worn synchro replacement if the gear is grinding in almost every circumstance. Gear popout is common with worn out gear dog engagement teeth or worn out slider engagement teeth. Gear grinding at any rpm is normally a worn out hub and slider or a severely worn synchro, while gear grinding at higher rpm is normally a worn out synchro with the potential for a worn out hub and slider from continuous grinding gear engagement.

Shifting issues can either be from worn out shift forks, worn out hub/sliders, worn out gear dog engagement teeth, worn out hub/slider keys, broken or popped out hub/slider springs, or excessive end play on the input and/or intermediate shafts.

With that said, it is very important to replace the input shaft and intermediate shaft tapered roller bearings on both ends of the shafts and then properly preloading the two shafts to tighter-than-OEM-spec tolerances. Each builder uses their own specs based upon power levels that the transmission will see. By increasing the preload on the input shaft you can also have the transmission slow down itself a bit to aid in high rpm shifting taking some of the load off the clutch and synchros to shift into gear as the input shaft will use friction to slow itself down a bit. By increasing the preload on the intermediate shaft you can allow for less deflection of the intermediate shaft under load or under increased temperatures which would cause case expansion resulting in the reduction of preload under increased temperature.

If you intend on doing alot of continuous load use in 3rd or 4th, it is imperative that you either service your transmission regularly, replace the 3rd/4th gearset/fork/rail for the heavy duty late 1991-early 1992 or Evo 1/2/3 parts along with tossing the aluminum shift fork as the expansion of aluminum will be greater than the steel parts under increased temperature resulting in substantially increasing the friction and potential binding of the 3rd/4th shift fork on the engagement surface of the 3rd/4th slider. This will result in permanent shifting issues and the potential for failure of the hub/slider or shift fork. If you are making ALOT of power or doing continuous load even with the heavier-duty 3rd/4th stuff, it would be wise to have an external transmission cooler fabricated up and have the return line spray onto the 3rd/4th hub and slider and 4th gear assembly to aide in cooling the parts down and maintaining lubrication to high-stress parts.



So....with that said, you can either take your chances with a stock transmission, or you can have it upgraded to suit your needs while having it gone through and inspected so you can replace the worn out parts before there is a failure that can easily cost alot more money than a rebuild.

Personally, if I was building it, I would recommend a stage 3 transmission that uses a custom chromoly steel 4-spider cross-shaft center differential, and a heavy-duty 3rd/4th gearset. If you are intending on shifting normal and not trying to put your hand through the stereo on 3rd gear shifts, go with the HD aluminum shift fork and have the 3rd/4th shift rail machined to incorporate a second roll pin (double-pinned 3rd/4th fork). If you don't know how to shift gently, then I would recommend getting an Evo 3 steel shift fork AND learning how to shift softer -- your transmission will last longer.

Along with all these things, don't forget to replace the clutch fork, clutch fork pivot ball, throwout bearing and have a properly functioning/bled/adjusted clutch hydraulic system to ensure that the clutch is properly disengaging, otherwise you will just put more wear on your transmission resulting in premature failure of more parts.


I hope that this long-winded tech response will give you more background into the workings of the AWD transmission so you make an informed decision in your purchase of an upgraded transmission. Like I said, you are playing with fire using a stock used transmission if it is not up to spec; especially if the bearings are worn on the input and intermediate shaft or the oiling shims in the center differential. It will only be a matter of when it fails, not if it fails.

 

[twicks69]

Also, regarding the PPG dogbox comment, if you have $9K in your back-pocket to waste on a transmission, then the PPG is the way to go. I still would not recommend this transmission with a single-disk clutch or in a street car. They still wear out over time, and substantially quicker if you are street-driving them and slow-shifting. Then, it will only cost thousands to replace used parts, instead of hundreds to replace used parts in a helical transmission.

Personally, some of the people here are looking at the upper limits fail points of these transmissions while you should focus on the sharp reality that less than 1% of the people here have ever produced a DSM with more than 500 AWHP. I think it is safe to say that less than 0.1% of the people are running a dogbox in a race car, and less than 0.05% in a street car.

I know alot more people running with more than 500AWHP that run stock/modified or built automatic DSM's and are more reliable. The weakest link they deal with in very high-HP/TQ applications are still transfer cases (which do have upgrades available).

So, take it with a grain of salt and do research (save money), or do it by trial/error (spend alot of money). I have done it by the latter, and only try to give DSM'ers the facts through experience so they can save money and make informed decisions.

 

[empie1]

Wow. That slo mo video is crazy!

 

[Calan]

Excellent info as always Tim.

 

[GRAVEDIGGER]

Wow. That slo mo video is crazy!

Yes, it is! It really shows how amazingly tough those viscous couplers are to hold up to that kind of abuse at all. This is why you just can't beat a welded center differential for drag racing IMHO.

 

[gofer]

The weakest parts in your 95-99 transmission (torque capacity wise) are the 3rd/4th hub and slider assembly and the stock center differential.

Yes it is...

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[empie1]

Yes it is...

hahahaha...what caused that?

 

[GRAVEDIGGER]

hahahaha...what caused that?

DSM Forums - View Profile: gofer

 

[gofer]

Shifting like a MFBA caused that, the worst part was when Shep called and said pieces of it also went into my center diff. case.

 

[twicks69]

Yup, been there done that. Sucks alot.

I should have learned after one broken before changing over to a different gearset. Instead, I tried a few more times and imploded a 3/4 hub, shattered synchros and exploded sliders from fast/hard shifting with the single disk clutch.

Modifying your driving style is the cheapest performance mod you can do to increase reliability of a transmission. Don't shift like a bad-ass, shift quick and light. I think I would recommend solid shifter base and shift linkage and shift linkage bracket bushings to increase shift feel so you can see how far you actually need to shift. It doesn't help that if the late 92-99 3rd/4th slider is notorious from exploding from shifting too hard into 3rd or from excessive torque under load. Heck, I have a 2G trans currently that the guy shifted so hard into 3rd he shattered the 3-hole late 92-99 shift fork at the same time, then continued to drive it with shrapnel destroying the rest of the transmission over time.

 

[gofer]

Heres another before I sent it off to Shep (sorry Tim)

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[empie1]

^ Hahahahahahahah holy shit...i thought my brothers trans was effed!!!

 

[gofer]

Mine was a 2-3 shift trying to get my NLTS setup for the track... I lost 3rd/4th gear but still had 1,2,5,R so I babied it to a buddies to take a look. After verifying the obvious... ...I left his house to baby it home and the trans. was locked in 1st, that was the longest 15 mile drive ever!

Thats not even half of the damage Empie, Shep is sending the rest of the damaged goods in a seperate box...