T56's like to break?

**570SX** · 07-20-2008, 05:07 AM

okay, when i first purchased my T56 out of a wrecked '01 Z, i figured i was buying the end-all, be-all of transmissions. hey, vipers and 'vettes use the same gearbox, how could i go wrong? well, i know now that there are some differences in them. but i see people upgrading the internal parts sometimes to Viper or aftermarket items. i've been searching and haven't found anybody actually exploding a gear or snapping a shaft. maybe this isn't that big of a forum or i'm just not searching for the right thing, i don't know. i know it's rated for 400ft*lb of torque, but that's irrelevant. i want to know what it can do, not what it was meant to do. i mean, that's why we all modify out cars, isn't it?

i don't drag race the car; it's for road racing. to that end, given the lack of weight, it will likely be ultimately limited to 450whp, maybe 500whp if i'm really stupid, but it will need to hold up to track abuse, hoosiers, and 500whp, and some standing starts, and whatnot. rear of the gearbox is all aces - my AL driveshaft is rated for 550ft*lb, and the stock 240SX rear end and axles will handle the power just fine with my current helical LSD. i just want to know if i'm going to be calling a tow truck on a very low race car w/ aero on it. i don't tow to the track, i drive it.

**squee** · 07-20-2008, 07:26 PM

I'd be willing to bet it would give out after some abuse. I think a Viper output shaft, new yoke (30 spline Mopar), steel shift fork, and upgraded keys should be plenty. Not many snap something. Most just start grinding or have trouble with the shift fork.

**570SX** · 07-21-2008, 05:38 PM

thanks for the info. i have more questions, if you don't mind.

so the 1-2 fork is already steel? i see the steel 3-4 fork is pretty darned cheap. the viper output, not so much. all of the bearings for the shaft, gears, etc. are all the same, just swap the output shaft itself? is the 5-6 fork steel as well? i don't see a replacement listed at all . . .

i'm sure as long as i'm pulling it open i'll hit the basics, too. synchro set, fork pads, full set of seals, maybe take my little shaping tool to the engagement teeth on the gears if they really need it, and check clearances and order shims if necc. you recommend replacing the output shaft, but the input is okay? or just harder to replace due to length/spline?

**squee** · 07-21-2008, 06:21 PM

Originally Posted by 570SX

thanks for the info. i have more questions, if you don't mind.

so the 1-2 fork is already steel? i see the steel 3-4 fork is pretty darned cheap. the viper output, not so much. all of the bearings for the shaft, gears, etc. are all the same, just swap the output shaft itself? is the 5-6 fork steel as well? i don't see a replacement listed at all . . .

i'm sure as long as i'm pulling it open i'll hit the basics, too. synchro set, fork pads, full set of seals, maybe take my little shaping tool to the engagement teeth on the gears if they really need it, and check clearances and order shims if necc. you recommend replacing the output shaft, but the input is okay? or just harder to replace due to length/spline?

I'm gonna try and answer all your questions to the best of my knowledge.

From what research I've seen, the 3-4 is the one to go, so I would assume its the only one not steel. The 5-6 might not be as well, but those are overdrives and should be a problem because you don't hit those often on a track. From what I know, the only major differences with the Viper tranny is the input and output shafts. The output is a common upgrade, the input, not so much because the length of it and the splines, like you said. The Viper can be used, but needs to be machined and your gonna need a new clutch. Both of which why I didn't recommend it. You can get a rebuild kit off of Ebay with syncros, upgraded bearings, etc. I've also seen them with upgrade options such as the fork and pads.

**570SX** · 07-21-2008, 06:40 PM

wow, i like the ebay prices. save some green. i don't know how the keys function, so here's another. is it better to get billet keys, or go with new stamped ones? if they're designed to be a wear part, i'd rather have them wear out instead of something more expensive, you know?

**squee** · 07-21-2008, 07:38 PM

Yea, I understand about the wearing. From what I've seen, billet is the choice of most.

**dwnshft82** · 07-30-2008, 06:09 PM

i have briken 2 street driving is harder than track all tho's 4 to 2 drops and itcanttake it i dont think you need to change the shafts inless theay break and that isent the problem common with t56 the gears are degined verry well and all the shift forks are not steel the main problem i have run into is the gears 1 buy 1 going and not being able touse theam i say fix the problem at hand with stronger shift forks and harder parts so theay dont wear out yes outher things can break after that but that is cous you fixed the week link and you are stronger and on to the next so that is my thout

**Danger731** · 07-30-2008, 06:20 PM

^ someone needs to go to sleep

**Spaz** · 07-31-2008, 06:48 AM

f-body t56's are different from vettes and vipers... they put cheap paper blocker rings in ours...

http://www.gmhightechperformance.com...ild/index.html

**570SX** · 08-04-2008, 01:27 PM

thanks! good article. :bookmarked: not that i didn't already have a nice exploded diagram, but the commentary is very nice when you're wondering what you really need and what isn't so necessary.

**ssweet99ss** · 08-04-2008, 03:20 PM

That is a very good article, Is there a place where you can buy all the heavy duty parts all as a kit ( all the upgrade parts)?

**blackbirdturbod** · 08-17-2008, 01:28 PM

Each tranny is diff. Mine gave out stock. My buddy has been running the same stock tranny with a built motor with spray right a round 800 hp running low tens. still hasn't broke!!! hes lucky...