So i got this 92 GMC Sierra 4x4 350 thorttle body when i bought it I new she needed some work like its got a bad exsust from the cat back hell the cat may not even be concted and it had a rusted out fuel line that the guy cut out and put a rubber hose on with hose clamps and its leaking alittle stil and the temp gage dont work for some reason, now the trany sounds like its going when shes cold she dont want to shift and even when shes wamed up on the hiway it losses power and dorps speed fast going 70 to 50 mph and if I try to give it gas it reves like its in nutral i have to ease the pedal till it picks up agian when im in town she dont shift al that bad, so any input on this would be nice I hate to put in a new tranny if that ant the problem but Im sure it is

 

I am assuming from the way you say it wont shift that either a standard with a bad clutch or an automatic with a transmission that is headed south as in junk and slipping needing a rebuild or replacement