Ford: 5 speed will not go into Reverse, rebuilder, quick test

Question
I have a 5 speed manual in my 1989 F150. I think it's the Mazda transmission. It was installed 2 years ago, off the shelf from a large rebuilder. It began being difficult to place in OD and after a few days won't go into OD and only half way into Reverse.

Answer
Do you mean the shifter is difficult to place into gear?

If so, then there is most likely a propblem with the shifter cable or linkage and not the transmission.

Quick test: disconnect the linkage at the transmission and , with thruck e-brake on and wheels blocked truck engine off, try to shift the transmission through the gears.