speedometer not working
 

Got a 71 chevy blazer and have no working speedometer. I have the cable spinning up tp the gauge. Is there a gear to replace or do I got to replace the whole speedometer?

Re: speedometer not working
 

If the needle doesn't move at all I would look for stripped teeth in the gears inside the transmission. Remove the driven gear housing (bullet). There is a plastic driven gear on the bullet and a plastic drive gear on the transmission shaft that turn the cable.

If they look good the next thing is to make sure the cable is inserted all the way into the back of the speedometer in the dash. Sometimes the part that screws in gets crossed threaded and the square end of the cable does sit all the way in and won't spin the speedometer. I check it by removing the speedometer bullet (drive gear housing) and with the transmission cable attached, spin it to see if the speedometer needle jumps (you will need someone to help you).

If those checks are good and it still won't move than the speedometer itself is bad and needs to be replaced.

Re: speedometer not working
 

Assuming that is up "TO' the gauge?

The steel square drive that pushes into the back of the speedo wears the plastic 'socket' in the speeedo. (some years are brass,, but more are plastic) Ya might try pushing the cable housing further into the speedo, and / or (if it's a replacement cable) moving the drive end just a tad longer to see if it engauges. Sometimes that works, sometimes not.

The aftermarket cables are crap to say the least, so try to keep your original if possible.