[C2] Speedometer Problem
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Le Mans Master
Joined: Apr 2013
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From: Arlington TX
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Speedometer Problem
After getting the right gear in the transmission for an accurate speedometer, the speedometer itself decides to act up. Pointer swings wildly and the odometer stopped working. Cable has been greased and plastic gear replaced. So is it time to pull the speedometer gauge and get it fixed & calibrated?
Drifting
Joined: Oct 2009
Posts: 1,728
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From: marietta, GA
After getting the right gear in the transmission for an accurate speedometer, the speedometer itself decides to act up. Pointer swings wildly and the odometer stopped working. Cable has been greased and plastic gear replaced. So is it time to pull the speedometer gauge and get it fixed & calibrated?
Thread Starter
Le Mans Master
Joined: Apr 2013
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From: Arlington TX
2024 C1 of the Year Finalist - Unmodified
2023 Restomod of the Year Finalist
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Yes, I’ve done all that. All new up to the speedometer housing. The reason I think it’s the speedometer itself is the pointer bounces around like it’s trying to work, but the odometer stays still.
Drifting
Joined: Dec 2014
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From: Chantilly Virginia
When you say "the right gear in the transmission" are you referring to the driven gear or the driving gear? If you are referring to the driven gear, was it working before you changed that gear? If the driving gear is the smaller diameter gear associated with higher rear end ratios, the correct driven gear may just tick the teeth of the driving gear enough to make the speedometer bounce around.
Thread Starter
Le Mans Master
Joined: Apr 2013
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From: Arlington TX
2024 C1 of the Year Finalist - Unmodified
2023 Restomod of the Year Finalist
2023 C1 of the Year Finalist - Unmodified
When you say "the right gear in the transmission" are you referring to the driven gear or the driving gear? If you are referring to the driven gear, was it working before you changed that gear? If the driving gear is the smaller diameter gear associated with higher rear end ratios, the correct driven gear may just tick the teeth of the driving gear enough to make the speedometer bounce around.
Le Mans Master
Joined: Nov 2015
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From: Really Central IL Illinois
Assuming the old driven gear you took out was working properly, and the new driven gear you put in are the same diameter, you should be correct. The only two things left are of course the ends of the cable and their connections. If the cable is properly seated on each end and the nuts are tight, it is no doubt in the speedometer. You could put the old gear back in to check the operation. What did you lube the cable with? Too much can be a bad thing as the lube travels up the cable to the speedometer head.
OOPS! I now see you changed the driver gear in the transmission to the larger diameter driver gear and thus needed the smaller diameter driven gear? I would still remove the new driven gear and look for evidence of incorrect mesh of the teeth or the cable spinning in the square hole before I pulled the speedometer.
OOPS! I now see you changed the driver gear in the transmission to the larger diameter driver gear and thus needed the smaller diameter driven gear? I would still remove the new driven gear and look for evidence of incorrect mesh of the teeth or the cable spinning in the square hole before I pulled the speedometer.
Last edited by R66; Aug 4, 2020 at 09:23 AM.
Melting Slicks
Joined: Sep 2005
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From: merritt island fl
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You can disconnect the cable at the trans, chuck it in a driill and spin it (drill in reverse) to verify.
Drifting
Joined: Aug 2004
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From: Galveston & Belton Texas
If the odometer Is not working you most likely have a bad second and/or third worm gear. Real common speedo issue. These two gears are available but require the internal head assembly to be taken apart. Wild needle swings are normally cable binding related. But, in your case the needle swing will probably go away with good worm gears.
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Thread Starter
Le Mans Master
Joined: Apr 2013
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From: Arlington TX
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Well, this morning I changed out the plastic gear in the tranny just to eliminate that variable and went for a drive. The speedometer went full sweep, back to 30, full sweep again, made a noise, then the pointer popped off and landed at the bottom of the gage. Think it was the speedometer head. Can it be repaired by a novice, professional, or buy new?
Drifting
Joined: Aug 2004
Posts: 1,294
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From: Galveston & Belton Texas
If you have a lot of patience, methodical and take lots of photos, then I would say you can take one apart and get it back together. The key is having the experience to be able to visually inspect before, during and after taking it apart and then also knowing what all is entailed for each fix. When you send to a qualified gauge restorer the last item will be properly calibrating by over charging and demagetizing the magnet/first worm gear. Pure guess but doubt that there are more than five members on this forum who have the knowledge and tools (electromagnet) to correctly calibrate. My recommendation is contact a qualified shop, briefly describe what happened and get a best case and worst case estimate.
Drifting
Joined: Aug 2004
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From: Galveston & Belton Texas
Appears you going to have to remove the speedo so one last thing. If your needle fluctuation was initially caused by the pointer not being firmly pressed on the needle stem, put your pointer back on and test spin rear of the unit with your fingers. You should get a half scale needle deflectIon and quick return to zero/or rest (you can adjust the pointer if it doesn’t rest exactly on zero later). This simple test let’s you know if the shaft freely spins and the pointer responds or the shaft is dirty or seizing. If it responded with a freewheeling finger spin then you may be able to replace the two worm gears I initially described. Additionally, you can rotate this rear shaft by hand to see if the odometer works. If they do not move at all I am sure you have a worm gear problem.
The speed cup, needle stem and hairspring are delicate so just hand them with care. Let me know if you need help on how to install/remove the needle. It is a simple procedure. Good luck!
The speed cup, needle stem and hairspring are delicate so just hand them with care. Let me know if you need help on how to install/remove the needle. It is a simple procedure. Good luck!
Last edited by tgtexas02; Aug 4, 2020 at 02:58 PM.
Thread Starter
Le Mans Master
Joined: Apr 2013
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From: Arlington TX
2024 C1 of the Year Finalist - Unmodified
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Do you know, TGTexas or anyone, where to send it for repair & recalibration?
Melting Slicks
Joined: Sep 2005
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From: merritt island fl
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I had my '64 done by Corvette Specialties of MD
www.csofmdwest.com
Pricey for me since Bubba had tried to fix it some time in the past.
www.csofmdwest.com
Pricey for me since Bubba had tried to fix it some time in the past.
Burning Brakes
Joined: Mar 2010
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I had my '64 done by Corvette Specialties of MD
www.csofmdwest.com
Pricey for me since Bubba had tried to fix it some time in the past.
www.csofmdwest.com
Pricey for me since Bubba had tried to fix it some time in the past.
Drifting
Joined: Aug 2004
Posts: 1,294
Likes: 295
From: Galveston & Belton Texas
I suggest you check the tri-five forum too if you are not sure where you want to send. The w-series speedo and tach assemblies were used from the 40’s into the 70’s in Chevy, Buick, pont, olds, and cad. The design never really changed in all those years. Point is, if the gauge repair shop can fix an old El Camino or Buick unit then they can fix a Corvette unit. Have to believe in the Dallas/Fort Worth/Austin area there is some one?
Drifting
Joined: Oct 2009
Posts: 1,728
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From: marietta, GA
Make sure you have the correct driven gear. If you go to LICS website, they will list the gear ratio and the color/tooth count.If you go to Joe Ray's corvette parts (ebay), he sells a fully reconditioned speedometer for $300 and will buy you old one for $100. He replaces the magnet, gears (metal not plastic), new face etc.
Thread Starter
Le Mans Master
Joined: Apr 2013
Posts: 5,003
Likes: 1,056
From: Arlington TX
2024 C1 of the Year Finalist - Unmodified
2023 Restomod of the Year Finalist
2023 C1 of the Year Finalist - Unmodified
I suggest you check the tri-five forum too if you are not sure where you want to send. The w-series speedo and tach assemblies were used from the 40’s into the 70’s in Chevy, Buick, pont, olds, and cad. The design never really changed in all those years. Point is, if the gauge repair shop can fix an old El Camino or Buick unit then they can fix a Corvette unit. Have to believe in the Dallas/Fort Worth/Austin area there is some one?