Okay so my old 76 GMC truck has speedometer issues. Specifically the needle doesn’t move at all.
I pulled the cable off the back of the speedo, and pulled the core. However it is still square on both ends, and gave the exact kind of resistance over the last couple inches I would expect while I was putting it back; so I don’t think the core broke. While the cable was off I played with the reciever spindle thing, and I could make the needle jump, so the meter doesn’t seem broken.
What kinds of fun things might I be looking at at the tranny end?
ALso I could turn the cable pretty easily in my fingers, with it seeminglycorrectly in place, from the speedometer end. Is that normal or a problem?
By far the most likely problem is that the inner speedo cable is broken. To verify, disconnect the cable from the driven gear housing on the tranny. If you turn one end of the inner cable, and the other doesn’t turn, it’s broken.
A less common problem is the speedo driven gear being stripped. If the cable is not broken, remove the driven gear housing from the tranny and inspect the gear. Expect to see some teeth worn nearly flat.
Rarely, the speedo drive gear might be stripped, if it’s made of plastic. The tranny rear housing has to be separated from the main body of the tranny to access this.