Here's one to chomp on. 2005 ccsb Z-71 5.3, 4l60E, G80....Wondering about the difficulty level and/or possibility of a bolting in a newer 6L60E in place of the 4L? Thinking it would have to have the '11+tune for shift points, but will that work with the engine? What kind of wiring issues, t-case issues?
Its been done but its not easy. You would need wiring PCM for the 6L60E since the PCM is faster. I think the 6L80E is a more durable trans for the truck. GM has never used the 6L60E in a truck only the 6L80E or 6L90E.
Also the tranny is longer so you will need a new drive shaft for the front and back.