I'm GMC, so am not allowed to play here
Hey wait Mr. Chevy Only Please, did you say you have an Izusaroo... I mean Isuzooka... er is it Isuzu? That's it, Isuzu! I guess maybe i can play after all. I am sure your truck has an ECM for that trans somewhere. In the earliest trucks, such as a '91 Suburban, it is under the dash behind the glovebox. I had a '91 with 6.2 diesel that was not computer controlled at all, but it had an ECM for the 4L80E because those are electronic transmissions. If you go with another engine that was available with 4L80E then you will need that ECM I would think. There are two VSSs on this transmission. It all matters since the trans reies on signals to work.