I've searched here and elsewhere and can't seem to find a definite answer. I'm looking at buying a 99 sierra 1500 for a beater, however it has no reverse or overdrive. The guy says that it is a common problem with these transmissions and he wants to sell it as is. It has around 175k on it. Any ideas what it could be, or if it really is even a common problem with them? Worse case is it would need a full rebuild I'm assuming, how does rebuilding one of these compare to an allison? What parts would you recommend I go with? Thanks for the help