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Speedometer Problems

1975 - Speedometer works, trip meter works, odometer doesn't. :wtf: What's up with that?

The speedometer has a steel worm gear that drives the odometer and trip meter. As the steel worm gear is located between the plastic odometer and trip meter gears it's entirely possible for the odometer to quit while the trip meter continues to work. The original speedometers used a nylon drive gear (to drive the worm gear) and now steel drive gears are being used because the nylon drive gears wore so much. You can either buy a new speedometer (around $320) or have yours rebuilt ($165 plus parts).
 

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Discussion Starter · #3 ·
The speedometer has a steel worm gear that drives the odometer and trip meter. As the steel worm gear is located between the plastic odometer and trip meter gears it's entirely possible for the odometer to quit while the trip meter continues to work. The original speedometers used a nylon drive gear (to drive the worm gear) and now steel drive gears are being used because the nylon drive gears wore so much. You can either buy a new speedometer (around $320) or have yours rebuilt ($165 plus parts).
Thanks for that. I google-searched and found the OD gear you mention, and it sells for a couple of bucks. Is it a big deal changing that out?
 

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Thanks for that. I google-searched and found the OD gear you mention, and it sells for a couple of bucks. Is it a big deal changing that out?

Give me that link so I can see if that's the gear I'm talking about. As long as your trip meter works the main drive gear at the bottom is still working. The only way your odometer can quit working is if it's gear is stripped.

As far as changing the gear goes it's easy to do but you have to be real careful pulling the aluminum indicator needle off so you don't destroy it.
 

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Give me that link so I can see if that's the gear I'm talking about. As long as your trip meter works the main drive gear at the bottom is still working. The only way your odometer can quit working is if it's gear is stripped.

As far as changing the gear goes it's easy to do but you have to be real careful pulling the aluminum indicator needle off so you don't destroy it.
Here's the link of the odometer gear in question. Let me know what you think. Thanks. http://willcoxcorvette.com/product_info.php?cPath=1810&products_id=979
 

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Here's the link of the odometer gear in question. Let me know what you think. Thanks. http://willcoxcorvette.com/product_info.php?cPath=1810&products_id=979

As your trip meter is still working that indicates that main drive gear isn't stripped. But as the originals were made out of nylon yours might be damaged. I suspect the driven gear that drives your odometer is stripped and I don't know how you could get one other than from Instrument Sales And Service (they are the folks who do all of the speedometer rebuilding).

Here's an AutoCad picture I drew of my new speedometer to show how it's constructed. Notice how it has a worm gear (standing upright in the middle) that drives the odometer and the trip meter.



Seeing how the odometer driven gear wasn't in line with the upright worm gear I put an additional two washers on the end to move the odometer over and into alignment with the worm gear. The main drive gear you found a link for is located under the odometer and trip meter and can't be seen.
 
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