4spd High RPM in 3rd Gear?

I have a 4 speed A833 Transmission it seems whenever I shift from second to third the RPMS jump way up, and I have to immediatley shift to 4th, seems like I'm in 4th anything above 35mph. It seems to act fine in 1st and second, then when I hit third it acts completely different. Anything I should try looking at?