How much does the stock T56 hold up (like rwhp wise). Considering one would istall like a Mcleod twin, 9 inch or 12 bolt rear, aftermarket DS,etc.And the car maybe doin 700-850 rwhp (just examples).. thanks......

 

horsepower is not what kills transmissions. Torque and traction is.

They are rated at 450 ft lbs. 500 ft lbs of torque on sticky tires is about all a stock T56 will take. The weakest link (providing the trans has good bearings and no play in the shafts) is the output shaft. If you're making more power, you'll want to upgrade to the viper shaft. There are a lot more upgraded parts as well.

 

damm! Guess I will be converting to auto. Thanks

 

I make the power in my sig with a stock t56 it tend to brake clutches and my 12 bolt also my wheel spin inside et streets. but the tranny has held up.

 

Do you spray off the line? The launch is really what will get to the transmission. Things like clutch burning and tire spin are also softening the blow on the trans.

They'll take the abuse of 600rwtq for a while, but eventually something will break or twist. You may even twist splines and not know it for weeks or months... Several launches later you just might snap the output shaft in half. Every one is different, but they all have their limits.

 

The other factor is your shifting technique. If you power shift, the 3rd gear fork will fail. I still have my original stock T56 running strong after 145K miles; 40K of those miles has been on a blown motor that puts out 593 rwhp. I don't speed shift and the car has seen 40 1/4 mile passes with sticky tires.

 

Ok, if I wanted to make my T56 more stout what upgrades I need? Like....
http://www.ddperformance.com/t56_partsupgrades.htm

 

LOL whats funny is that the auto is weaker than the manual and u want to switch to the weaker

 

FWIW, those torque readings are taken at a constant rate over a long period of time (like 12 or 24 hours). The T56 will take shock loadings of a lot more torque than that rating. I personally know of a few guys running bone-stock T56s in LT1 f-bodies with over 600rwtq for many, many track passes.

But like Roadie and OBE1 95Z28 said, you must treat it with some decent manners at those power levels. Once you begin yanking that shifter with all your might, the stock forks and synrco teeth will fail. I think that's what killed my transplanted '97-model T56 late last year... and i'm putting out 290rwhp/320rwtq at the most (never dyno'd, projecting from what others with close to my setup have dyno'd). I took it apart this summer and the teeth on the 2nd gear syncro were ground off; the other syncros looked almost new. I'll never powershift this trans again (or any other for that matter, after seeing many people with well over 600rwhp/rwtq nail a stock T56 over and over i thought it would strong enough to take any kind of abuse i could throw at it at my power level... oh well).