Wakko

A friend of the family is currently incarcerated and likely will be for a while. His '07 Avalanche is under my care and we are trying to decide what to do with it. He bought the truck new and souped it up a bit but when the drug monster came he trashed the truck. Truck has about 130k on it with a replacement motor from Chevy and original tranny. Before he got locked up his girlfriend was driving it and somehow grenaded the rearend at highway speed, so of course the driveshaft popped out and much of the tranny fluid came out before she shut the motor down. We put a junkyard rearend in it and the truck runs/drives fine now, but reverse is slipping and just about shot. I did some searching and found this thread:

https://chevroletforum.com/forum/sil...reverse-57358/

Does that apply to the Avalanche? I don't want to put $2,000 into the truck to sell it but know if it's fixed it will bring in more money. What's the best way to diagnose it so that the local tranny shop doesn't say "Tranny's shot...$2,000 rebuild." when it may just be a more simple repair?