so my old one was broke because when i took it off the cable came right out, so i got one from the junk yard and it dos work cus i hooked it all up and used my drill to turn it and it went to 40 mph but when i screw it into the T case and drive nothing happenes,,, so whats going on

 

My speedo cable was the same way, but I had to replace the whole speedometer cable housing because of cracking and rusting. One thing I noticed was the cable needed to go into the Tcase one way and one way only. if it isn't in properly that could be the problem.

 

there is a small plastic gear inside of the cactual unit that some times strips out i would check that

 

alright thats what i was thinking that there had to be some little gear thats missing but wasnt sure how common that was, do i have to take off that first plate on the Tcase