All I know is that the gearing is different in the two different trannies, but is there a difference between longevity and what the trannies are rated for in torque?......

Thanks.

 

There are several stock t56's and the aftermarket version. The transmissions are like a four speed with two overdrives. Fourth gear is always one to one. The most common trannies are 94 and later with a 2.66 first gear. This is .12 deeper that a muncie four speed so you dont need a real deep rearend ratio. Most guys in here are going with 3.73 The factory used a 3.42 with these boxes which isnt deep at all. a 3.30 to a 3.73 would work good for street use. The first year they made the t56 was 93. trannies came with a 2.97 or 3.36 first gear, and an overdrive of .62. These trannies are weaker than the 94 and later trannies . The t56 with the 3.36 is rated somwhere around 350 lbs of torque. The tranny with the 2.97 is rated at 400 lbs of torque. the aftermarket t56 has the 2.97 first gear and .62 overdrive. It is rated at 400 lbs of torque. Most people go with a 94 or later t56 because they are more common and they are rated at 450 lbs of torque. Any T56 from 94 to the time they started using the ls1 would be a good choice.