today i was tightening down my speedometer cable where it meets the transmission and the plastic piece with the threads broke off and it's part of the tranny not the cable.. i tried taking the part off, there is jsut one bolt holding it but fluid starting coming out so i left it there.. anyone know the name for this piece?? it's the part that the speedometer cable screws onto on the tranny.. THANKS

i have a 1983 auto 4speed

 

I broke mine also, and have problems since. I also broke the plastic gear inside .
I have the digital guages on my Iroc-Z and the speedometer is the only thing not working because of that. I tried 91Z tranny plastic gears and electronic speedo sender but I cant get it to work? Any help on this matter would be greatly appreciated.

 

You can get the new speedo gear hosuing thing at the dealer. In fact, a new one will be steel; an altogether better part than what was in there before, which is made of unbelievably crappy soft material. It wasn't plastic, actually, it was chinesium.