Shifter or tranny?

[Lobo'74]

Just took the truck out for a spin. Coming back home the shifter wouldn't come out of first. When I forced it a bit (VERY stiff) I could get it to neutral, but it sounded like the grinding of a non-syncromesh trying to shift. I couldn't get it into second. I was in my neighborhood and got it home in first but had a little trouble parking since it wouldn't go into reverse either.

So, how can I tell if it is the shifter gone bad (that's gotta be rare) or tranny gone bad? Its an all syncro three speed fron a '79. The shifter is an old school Fenton.