i recently bought a 1994 chevy 1500 4x4 with a 350 in it the trans is bad it doesnt shift into 3rd or 4rth
i am goin 2 put a trans in it but the truck runs fine but when u put it in gear or underload the rpm drops and stalls
it idles fine and at the rpms it should

 

When you say underload do you mean you can get it in to gear part of the time?

 

Have you checked your filters? If not do a mild tune up and change your air and fuel filters.

 

my filters fine new plugs and wires some one toll me the trans being bad is a censor the jus off the truck if somthings wrong i
dont know if i beleave that but what do i know when i mean under load like in drive or reverse maybe the fuel filter i did not think about that

 

If you haven't changed your fuel filter it wouldnt hurt anythig, what your friend say sounds like the torque converter lockup switch (not sure it that's what it's called).
It will kill it when you try to drive. That is like popping the clutch with your foot on the brake.