i look at a 86 pick up today , everything was good during the test drive until it went into 4 wheel drive. it sounded like the drive shaft was binding up and making the whole truck bump. what could this be from

 

Were you on pavement, did it occur when turning if so thats normal and dont do it again. Other words you might have different tire sizes or even gear ratios.

 

I tried it on pavement and gravel going straight and it has stock gears and 33's and it only happens when the hubs are locked

 

i had a problem like that and it was bad cv shaft, but if the u joints are bad that could cause it too.

 

4-low always binds up just a little bit at full turn, But going straight there shouldn't be a problem.
Either there are different gear sizes front and rear, or your cv's could be bad.
(Assuming its something small)

 

could the cv's go bad from sitting the guy hasnt driven it for a year or two

 

and he said everything worked when he parked it