Info and help Re: wiper transmission

I have a 67 Dart. When I got it all was disassembeled. It came with a 3 speed wiper motor but 2 speed switch? I got a 2 speed motor and all works. I believe my problem now is the transmission. Ive been reading and searching but still unsure. Is there a difference in the 2 speed and 3 speed wiper transmission? Is it just the piece that goes to the W/motor crank? I have like said,2speed motor,switch and bushing but the bushing and transmission arm don't want to work at wiper motor crank. Thanks for any clarification....:coffee2: