3.9L Cummins/Isuzu diesel swap in 89 Suburban

[79c25]

Originally Posted by 87Skier

Why not use the 4L80? Personal preference? I was thinking of using it because of the cost of finding a manual transmission and having to convert my auto to manual. I really like driving manual transmissions though.

I don't feel that it's a reliable choice behind a 12 valve UNLESS you get it built to handle it. First generation 12s put out 400 lb ft of torque and if I remember right the 2nd generation put out 450+, the 4L80E is rated for ~350 lb ft stock. It might last a while if you are extremely nice to it though.it should do ok behind a 3.9, but once again,you have to be easy on it unless you get a built one.