I am running an E38 from a 2008 Yukon OS1250216 and a T42 computer and harness from what I believe to be a 2007 Silverado OS24239927. I had an older 4L60e in it that lost 3rd and 4th gear (possibly from wrong tune settings?). I just picked up another 4L60e from a 2009 Silverado and installed it.
The problem is that the trans is going into 2nd gear only. I believe it has communications, as the scanner tool showed trans temp and gear selector position. I can't even get it to take a command for a different gear or lock the TCC with Scanner. Is it possible that I need a T42 from a newer vehicle with this trans? If so would I have to add the additional wires and repin my TCU connection?
Thanks,
Joe