Blackdog76

I have a 6.0 out of a 2002 Denali and bought an early model (1991) 4L80E without knowing there was a difference between the years. The first thing I noticed was the electical connector on the side wasn't going to work with my harness. TCI has replacement internal wiring harness that adapts the early model transmission like I have to the later model wiring and connector. I talked to the tech at TCI and they claim that when I swap this harness out, my 4L80E can work as a late model one. I would think that they are the experts but I still can't belive it. There were a number of changes according to the ATSG manual. They list the following:
Updated Electronics for 1994
Updated Center Lube Sustem for 1997
Updated Manual 2nd Band for 1999
Updated Overrun CLutch for 2001
And, someone else told me that the valve bodies are different also. Since I know nothing about transmissions, should I just sell this one and get a newer one or try to make this one work?

Blackdog76

Kind of a tough question, I'll try somewhere else.

whitt1

Are you going to run the transmission with the stock PCM or a TCI computer?I wouldn't even consider running the 91 transmission with the PCM,because you will have problems with the range switch,which is different on the 91 model.I'd go with the later model transmission.

Blackdog76

I was considering using the PCM. I think I might sell the transmission for a newer one. It would be far too much work to get this one going. Thanks for the input.