What kind of 4 spd? If you have a car transmission or one with an external linkage, it sounds like the linkage is hung in 2 gears. Obviously if it's a truck trans, that's not the case. The old 3 on the tree was bad for that, too. I've not seen a truck trans do it but it might be possible.
I've seen other posts for this same problem, I'd like for someone to tell us what they found.
Looks like I answered too quick, being a 1 1/2 ton it must be a truck trans.

Last edited by Mearl; 01/08/2011 8:50 PM. Reason: didn't have all the facts
'65 C-10, 65 L-60, 65 C-80, 72 C-60 & and a bunch of old Chevy cars.
Never time to do it right, always time to do it over.