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I am driving along in the ’62 and as soon as I hit about 30 mph the speedometer goes crazy, starts making a loud grinding sound, and the needle starts jumping back and forth from 30 mph to 160 mph. I slow down to about 10 mph and the noise goes away and the needle returns to normal, speed up to about 25-30 and the noise and needle jump returns. I disconnect the speedo cable and finish the trip. Back home in the shop I hook up a drill to the speedo cable and get the same problem over an indicated 25 mph.Looks like I am going to have to remove the speedometer and get it repaired.
Any recommendations on a repair shop?
I used Corvette Specialties of Maryland about 15 years ago and was pleased with their work. I looked on the internet and found Corvette Specialties of MD West located in CA. Anyone know if this is the same company?
Is there such a thing as a repair manual or instructions on speedometer repair?
Thanks,
Charles
Last edited by cbernhardt; Oct 24, 2022 at 07:16 AM.
Before you do that try greasing the heck out of the cable
I lubed the cable about 5 months ago. When this problem occurred I pulled the cable and it was well lubricated, but I applied more lube, replaced the cable and the problem was still there.
I lubed the cable about 5 months ago. When this problem occurred I pulled the cable and it was well lubricated, but I applied more lube, replaced the cable and the problem was still there.
How is the drive gear in the trans? Always better to check the easy stuff first.
make sure you have no hard 90 degree kinks in the cable also.
mine did that... it was a '70 so your's may be different.. but eventually the speedo drive gear ( not the plastic driven gear) in the tailshaft of the tranny had to be replaced.. it was plastic, I put in a metal one.. problem solved.
but replace the plastic driven gear at the cable connection as a 1st try....
this ... or this
you can get a metal one, talk to paul from 5speeds.com , he's a genius.
Thanks for the suggestions, BUT I am not using a transmission drive gear. The speedo cable is driven by a Cable-X unit which converts the transmission electronic VSS signal to mechanical.
I checked the Corvette Specialties of MD West website and to repair the old speedometer is probably going to cost $350-&450. I have converted a C1 mechanical tachometer to electric so another thought - does anyone know if the mechanical speedo can be converted to electronic? I don't think converting the speedo part would be too difficult, but the odometer part might be a problem.
Charles
Your speedometer acts like there is something amiss in the unit itself. There is no physical connection between the needle and the cable. It's just a spinning magnet in a metal cup. The magnetism turns the cup/needle. Sounds like the magnet is in contact with the cup, or some debris has entered the area making a physical connection between the magnet and cup.
That particular area has not changed in a Corvette/chevrolet speedometer since 194x. The odometer gear (part of the magnet assembly) stripped on mine. After two Chinese speedometers and both failed, I decided to repair my original.
I'm currently using a magnet/shaft assembly from a 1947 chevy pickup speedometer, same as my 1970. A speedometer is not difficult to repair. Most don't want to go there.
You first need to determine where yours has failed. If you did want to attempt a repair yourself, I can assist if you wish.
Your speedometer acts like there is something amiss in the unit itself. There is no physical connection between the needle and the cable. It's just a spinning magnet in a metal cup. The magnetism turns the cup/needle. Sounds like the magnet is in contact with the cup, or some debris has entered the area making a physical connection between the magnet and cup.
That particular area has not changed in a Corvette/chevrolet speedometer since 194x. The odometer gear (part of the magnet assembly) stripped on mine. After two Chinese speedometers and both failed, I decided to repair my original.
I'm currently using a magnet/shaft assembly from a 1947 chevy pickup speedometer, same as my 1970. A speedometer is not difficult to repair. Most don't want to go there.
You first need to determine where yours has failed. If you did want to attempt a repair yourself, I can assist if you wish.
Barry
Thanks for the offer of assistance. I will not be able to remove the speedometer for several weeks, so I may contact you then.
Charles
I am driving along in the ’62 and as soon as I hit about 30 mph the speedometer goes crazy, starts making a loud grinding sound, and the needle starts jumping back and forth from 30 mph to 160 mph. I slow down to about 10 mph and the noise goes away and the needle returns to normal, speed up to about 25-30 and the noise and needle jump returns. I disconnect the speedo cable and finish the trip. Back home in the shop I hook up a drill to the speedo cable and get the same problem over an indicated 25 mph.Looks like I am going to have to remove the speedometer and get it repaired.
Any recommendations on a repair shop?
I used Corvette Specialties of Maryland about 15 years ago and was pleased with their work. I looked on the internet and found Corvette Specialties of MD West located in CA. Anyone know if this is the same company?
Is there such a thing as a repair manual or instructions on speedometer repair?
Thanks,
Charles
Yes Brian Tilles company..i used them for my 58 and 59.
Kind of a general question without a single answer.
I attached another photo from someone else. Most of the parts are not available. "B" is available, "A" (input shaft and magnet - cannot find any supplier)
The rest of the items 1 thru 6 don't seem to be able to be sourced, and don't seem to wear out often.
In my case, "A" & "B" had worn out gears. I replaced "A" from a doner speedometer, 1947 chevy pickup.
cbernhardt,
I have the guts from a 58-62 speedometer. Don't know if it works, but I can try to connect a drill motor and test if you are interested.
Charles
Mine did that for a while after I put the car on the road. I found out the cable end was too long going into the speedo head. It was going in too deep. Might be worth a look.
I sent my speedo/tach for my C2 to Joe Ray in Little Rock and he did a great job. I don’t know if he does C1’s but would think he could. Sorry, don’t have his contact info but you can do a search.
Mine did that for a while after I put the car on the road. I found out the cable end was too long going into the speedo head. It was going in too deep. Might be worth a look.
The speedometer has been working properly for over 20 years and 50,000 miles, so I don't think that is the problem, but I will check it after I get it out.
Charles
I had the same issue---what I discovered is that when it makes that kind of noise it needs to be repaired. Greaing wont do it.
I used the one you found---he was from MD but relocated to CA. His service is first class.
You buy a rebuilt one from him--off the shelf. he sends it to you free shipping and also includes a shipping label.
You use that label to send him your old unit which he will rebuild and re-sell BUT he BUYS it from you----and sends you a check. Think he gave me 150.00 for my old one.
With his system you get the new speedo within days as opposed to waiting weeks to have yours rebuilt.
I was extremely happy with the way it worked as well as the result.
Eddie
Speedometer problem
