I recently bought a 75 Highboy from a family friend. It sat for 19 years and the owner would start it up once a year. I got running pretty good and changed all the fluids but when I drive it the tranny will slip. The owner said he'd never had problems with the transmission before. He had swapped the motor and tranny from a 77 f-250 into it from a 4 speed and out an automatic tranny in it, I'm not too familiar with fords so I have no clue what transmission is in it. But he put a B&M ratchet shifter in it. The shifter is super loose and is hard to get into gear. I think the linkage could be messed up on it. Could this be what's causing the slip? Any other ideas?