1971 Econoline E-100

I have a 4-bbl Ford 302 that runs alright now. My tranny, however, isn't in the best condition. If put in "D" it will start out in 2nd, and shift to 3rd waaaay up in the RPM's. If I pull the column down to 1st, I can shift up to 2nd manually, but it won't go into 3rd.

What could be my problem?

EDIT-I think it's a C4 transmission, but don't know for sure, as it's a ways away and I'm at school.