Tranny or TC issue?

[BC.K5.78]

New to the forum. I looked in previous threads did not find what I was looking for so here we go.
I have a K5 already and was looking for a parts truck. found one with the same tranny and TC ( th400, np205) he says the motor has little compression and barely moves in 4low. To me that sounds like a tranny or TC issue. and the main reason why I'm buying it is for the TC. ( mine got run over by a D6 cat ) anmy suggestions would be great.

Thanks

 

[76zimmer]

t/c is all gear drive, so if it moves at all the t/c should be good...the trans can obviously slip..burnt up clutch packs or other issues...fluid would be brown or black if that's the case.
Brakes froze up on it?
Pop a plug or two and do a quick compression test?

 

[6.2Blazer]

When he says it barely moves in 4 low, does that mean it drives fine in high range or 2wd, or you have to put it in 4 low just to get it to move? If the trans was slipping really bad it may not move in high range but may in low range simply because the trans does not have to output as much torque to move the truck.

 

[BC.K5.78]

Those are all questions i just asked. thanks. its 2 hours away so i don't want to make the trip pulling a trailer for nothing