I have a 78 Ford with a 521 v8, making about 550hp and about 550 ft lbs. Its in front of a stock c6 other than a shift kit. It could make alot more torque, I am wondering if that c6 can handle 650 ft lbs? Id like to have it last a while...the tranny has a 109,000 miles on it.

add on: well drove it again, and its starting to wear out. its not unheard of that a c6 with a stock engine in front of it will last 200,000 miles...stock tranny is meant for 250 ft lbs input torque. im 55 to 60% over that, do the calculations and the transmission will start getting worn out around a 90,000-110,000 miles.

 

At that mileage, I'd rebuild it before expecting it to handle much more than a stock big block. A fresh stock C6 would handle that, but not for too long.

 

well its still seems to hold okay

 

Somewhere in the area you are talking, north of 500 horse, the case will flex. They used to put a girdle on them where the pan bolts up, but not sure if that "fix" worked or is still used today.

Check outfits like this for the list of parts they add for high power applications:

TCI Auto: Super StreetFighter™ Transmission; '66 & Later FE C6 13 1/2" Tailshaft (332/352/390, 406, 427, 428)

 

i put a TCI streetfighter in my truck... burnt up last summer, so i found heaver and put that in over winter.... second gears almost gone and its only april.. so im goin 2 a 4spd

 

I drove it again the other day, it is actually getting tired. When i drove it normally it shifted fine but when i got on it real hard it jumped from the 2-3 shift....couple hundred rpms...It did that for the past few thousand miles at all throttle positions when my brother had it, so i adjusted the band and it shifts fine at normal throttle, but when the pedal is in the fun position it slips a bit.