C3 Speedometer
Thread Starter
Cruising
Joined: Feb 2024
Posts: 14
Likes: 0
C3 Speedometer
Yesterday the temperature dropped to 25 degrees, guess I didn't move far enough south. In any case the speedometer in my old 120K mile C3 quit. When the temp got above freezing it worked for about 1/2 mile and quit again. Too cold to dig into it right now but I'm wondering if the cruise control transducer could be the culprit? Is there a way to bypass the transducer? Like connect the cable from the transmission to the cable to the speedometer? If it warms up a bit I'll disconnect the cable from the transducer and hook my hand drill to it and see if the speedometer is operative. Hmmm...wonder which way the cable should rotate, CW or CCW? Afraid if I run it backwards it will damage the speedometer.
Racer
Joined: Nov 2017
Posts: 319
Likes: 125
From: Midwest
Safety Car
Joined: May 2001
Posts: 4,747
Likes: 1,642
From: Fairfax Virginia
I had the same experience with my 1968 C3 in the cooler weather. It turned out to be the lubricants they used became hard and brittle with the colder weather and this led to damage to the speedometer. I had it repaired and it works fine today. Some times the 57 years will take their toll on the Corvette.
The window tracks used on the older C3's like mine had this white/grey lubricant on the tracks and it was hard as a rock. Using a Hot Air Gun I was able to heat it up and remove it completely before applying a new lubricant. The door lock hardware can get gummed up as well so with a hot air gun you should be able to clean that up as well. I used a lubricant that works when hot or cold and doesn't freeze up.
Now my Motorcycles Speedometer is starting to make a bit of noise as well. I might try and rebuild that one myself as I have spares for that system.
The window tracks used on the older C3's like mine had this white/grey lubricant on the tracks and it was hard as a rock. Using a Hot Air Gun I was able to heat it up and remove it completely before applying a new lubricant. The door lock hardware can get gummed up as well so with a hot air gun you should be able to clean that up as well. I used a lubricant that works when hot or cold and doesn't freeze up.
Now my Motorcycles Speedometer is starting to make a bit of noise as well. I might try and rebuild that one myself as I have spares for that system.
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,809
From: Cool Northern Michigan
Jimmy,
If you run your drill backwards, it's the same as driving backwards at high speeds. So, keep the RPMs down.
You did not mention if plan on using the Cruise anymore. Some of us did away with luxury options that quit working.
If you do bypass the transducer for good, you can purchase a longer cable from a Vette vendor.
Basically there are four lower cables to choose from.
4 -speed w/o cruise
4 -speed w/ cruise
Auto w/o cruise
Auto w/ cruise.
If you do swap out the lower cable to by-pass the transducer, have a helper near the firewall be ready with new cable end. As you remove the old cable from under the dash, the helper can hand you the new end. God awful place to work on lying on your back.
If you run your drill backwards, it's the same as driving backwards at high speeds. So, keep the RPMs down.
You did not mention if plan on using the Cruise anymore. Some of us did away with luxury options that quit working.
If you do bypass the transducer for good, you can purchase a longer cable from a Vette vendor.
Basically there are four lower cables to choose from.
4 -speed w/o cruise
4 -speed w/ cruise
Auto w/o cruise
Auto w/ cruise.
If you do swap out the lower cable to by-pass the transducer, have a helper near the firewall be ready with new cable end. As you remove the old cable from under the dash, the helper can hand you the new end. God awful place to work on lying on your back.
Racer
Joined: Nov 2017
Posts: 319
Likes: 125
From: Midwest
Strictly speaking, I believe there are only two lower speedometer cables to choose from, as cruise was only available with automatic transmission from the factory.
Auto w/o cruise
Auto w/ cruise
But, who knows? I could be wrong.
Having said that, I did purchase and fit a lower speedometer cable (Auto w/ cruise) to my car that has the M-21. The four speed is factory original. The car also has an original type cruise control setup, but I've always assumed a previous owner installed it since Chevrolet wouldn't. I really like the configuration of the two (upper and lower) speedometer cables joined by the transducer. I will probably get the cruise control working in the future.
--------------------------
1979 L82 M21 FE7
Classic White / Doeskin
Auto w/o cruise
Auto w/ cruise
But, who knows? I could be wrong.
Having said that, I did purchase and fit a lower speedometer cable (Auto w/ cruise) to my car that has the M-21. The four speed is factory original. The car also has an original type cruise control setup, but I've always assumed a previous owner installed it since Chevrolet wouldn't. I really like the configuration of the two (upper and lower) speedometer cables joined by the transducer. I will probably get the cruise control working in the future.
--------------------------
1979 L82 M21 FE7
Classic White / Doeskin
