I just bought this 1997 ford F450 and the reverse dosn't work. The shifter will go into the reverse position but nothing happens when you release the clutch. 5th gear also grinds a little but nothing serious.

Any ides as to what might be wrong and is it worth repairing or should I get a used trans from the junk yard. Are gas zf5s and diesels zf5s the same?