I've got this 1991 Chevy that's 4l80e has gone south. I'm lead to believe that the 91-93 style transmission with the Bosch force motor and cleaning cycle is inferior to the 94-96 style, and would like to install a Hughes 4l80e, which they list as fitting 1991-96, which I'm assuming means the later style transmission. TCI is in the same boat, lists one part number for that whole year range. After doing some research it looks like my easiest solution would be to install a later 7427 ECU with $31 code in place of the stock ECU and run the later transmission. I found this whole thread which made me decide to tackle the project at all. After a bunch of reading it looks like all I really need is the ECU, I've got a spare Moates adapter, programmer, and datalogging cable.

Other than swapping the ECU harness over, what else am I looking at changing on the 1991? I read that the VSS circuitry changed but is forwards compatible, but not backwards compatible, but that I should probably swap to a later style DRAC and that I'll probably need to change the knock sensor as well? Are there any other big gotchas that I'm not seeing on this project? Thanks for any help.