Speedometer jumpy and odometer doesn't work. The speedometer needle seems accurate but seems jumpy and the odometer numbers don't move.

Do I need a new or rebuilt speedometer and/or speedometer cable?

 

Mine did that it was a worn out gear in the odometer

 

Have you checked if the odometer reset **** is stuck in the up position?

 

That reset cable gets sticky and sometimes is in "limbo" where it does nothing. Push it UP to see if it can move further and re-engage the odometer drive gears.

As far as "needle jumping" on the speedo.... that is usually due to a sticky cable, rubbing on the inside of the cable sheath. NOW is the time to pull that cable and TRY to fix it with some lube. Depress the retaining clip on the rear of the speedo to pull the cable loose from it. You can pull the entire cable out from that end you removed... BUT place a throw-away shop towel around the cable and cable end as you draw it out, using the towel to wipe off any dry or wet lube AND keep that lube from dropping on your floor mat or carpeting!!

If you see any unwinding of strands on the cable or areas where it has obviously been rubbing inside the sheath, consider replacing the entire cable. Once the inside of that sheath starts to deteriorate, its only a matter of time till 'cable-whipping' causes damage to the speedo head.

If the cable had any grease or wet lube on it, clean it ALL off well with lacquer thinner or other non-greasy solvent. Then put a squirt (?) of DRY graphite lube in a shop towel and drag the cable thru it so that there is a fine layer of graphite on the whole length. Insert it back in the sheath and make sure that it goes completely in (it has to engage in the square-drive socket in the trans speedo driven gear). Depress that clip and install the end of the cable into the speedo. Test it out to see if you resolved the issue. If not, replace the whole cable set.

 

My odometer stopped working a few years ago. (Trip & Main odometer) The #2 gear in the speedometer stripped. ( Where the main shaft comes in from the speedo cable is the # 1 gear. #2 is the driven gear from # 1)

My needle also was jumpy, this was a result of the stripped gear catching and jamming for a second causing the needle to bounce.

I ordered a new #2 gear, however the main gear (#1) was too warn and the new gear would not mesh properly with the #1 gear. It would jam and seize the cable. You can try a new #2 gear and see if it works. Check it by hand before installing. If it seems well, then try with electric drill. If good then install.

The #1 main gear, as far as I know, is not available. However, GM did not change internal workings of speedometers over the years, so i was able to source a good #1 shaft/gear from a 1943 Chevy pickup, it was in perfect condition and was exactly the same dimensions as my 1970 speedo gear.

You may not want to this much work into fixing your speedo, however I fixed mine for less than $10.00 A speedo repair shop would be much easier, however I live in Canada, so no such place.