My odometer stopped working. The speedometer works fine. I assumed that some of the gears are broken and ordered the second worm gear. I changed it today, but the speedo sticks when turned counter clockwise. It turns clockwise but needs tampering to turn the correct way. Apparently the first magnet/ worm gear is worn as well and jams the second gear.

I have not been able to find the part anywhere. Is the second gear only part that can be replaced? Are the other gears sold somewhere?

Any tips are welcome where to find the part. The dash is in pieces and I would not like to do this again anytime soon..

BR Pekka

 

http://repairs.willcoxcorvette.com/?...ive-gear-53-77

 

I think this is the link caskiguy was trying to post... but replacing the second worm gear would just be a band-aide.


http://repairs.willcoxcorvette.com/1...-stop-working/

 

Last Summer my speedometer did the exact same thing. I also purchased the "second" worm gear and had the exact same results, jams when turned.
I pressed out the first gear/magnet ***'y from the housing and the first gear was very worn, causing it's worm to ride out of the second gear groove.

I had no success in finding a new first gear. Also, if you did find a first gear/magnet, the speedometer would need to be calibrated again.

I purchased a new replacement speedometer.

Some additional information...
I believe that any late '60's early '70's GM speedometer likely uses the same first gear. The housing would not likely be the same, you would need to press out the first gear and use that only.
I found reference on the internet that the c3 corvette mechanical tach uses the same gear/magnet ***'y. (Obviously the gear would be good)

You can calibrate your own speedometer if you do find a replacement first gear..
Run the speedo cable under the door to inside of the car. Connect the repaired speedo to the cable, then go for a drive. Have a helper with a GPS establish the correct speed, adjust the speedometer to match.

If you find a source for the first gear, please post. I would still like to repair my original.
Barry

 

First worm and magnets are readily available from the fact that the tachometer used the same parts but they didn't drive the odometer so the first worm is always good on an old tach. So a good replacement first worm would be finding a decent tach to scavenge the first worm and magnet from. The issue is the cost... If the first worm bushing is bad in the speedo, (and we make this bushing from oylite) then you have to press out the first worm bushing, find a good first worm and then calibrate it to the head.. As bad as I hate to say it, the cost to do this exceeds the price of just buying a new speedo.... IMHO... -Willcox

 

Thanks! Excellent information. As it happens I have the old tachometer from the same car as spare so I can try to use the first gear. I would have never guessed that the parts are similar. If that is not working I will just order a replacement. I will post the result if I can make this work.

 

Found this on the internet, they may sell parts as well.
https://www.csofmdwest.com/speedomet...r-restoration/

 

Seems to be working now! Both meters have the same frame. I took the frame with the first gear from the old mechanical tachometer and used the rest of parts from the speedometer. Most probably the tachometer works as well with the speedometer frame and gear. I guess the calibration needs to be done somehow next. There is about three feet of snow outside so that needs to wait a bit..
Thanks!