Speedometer and odometer refurb
Thread Starter
Drifting
Joined: Jul 2012
Posts: 1,255
Likes: 297
From: Slovenia, EU
2017 C3 of Year Finalist
Speedometer and odometer refurb
Hi,
my odometer stopped working plus my speedometer started to making a ticking noise. It works but is ticking.
What parts do I need to refurbish this?
Cable to the tranny or just the gears in the tachs itself?
Anybody did this already?
my odometer stopped working plus my speedometer started to making a ticking noise. It works but is ticking.
What parts do I need to refurbish this?
Cable to the tranny or just the gears in the tachs itself?
Anybody did this already?
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,851
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
On any speedometer.. 1953-1977....
If the odometer is not working.. the speedometer needs to come out and be serviced.
When the first worm bushing wears out.. it puts the first worm (A) in a bind with the second worm (B). The first, second, third and fourth gears are what drive the odometer and the trip odometer. When the first worm binds with the second worm it eats the teeth off the gear. This stops the function of the odometer.
Once the bushing gets worn enough the first worm magnet will start hitting (scrapping) the speed cup... This cause erratic needle jumping and moving. The speed cup has a shaft on it that the needle attaches to and when the first worm bushing gets bad enough it will eventually grab the speed cup slamming the needle and in most cases breaking it and the speed cup.
Replacing (and they are available) the second worm gear with the plastic replacement is only a band-aide and actually a huge waste of time considering how hard it is to remove the speedometer from the car.
Other items that can cause a speedometer to be jumpy would include: Defective or binding speedometer cable, worn driven gear in the transmission, cruse control transducer(on equipped cars). The previous items can cause bouncing but anytime you have a working speedo with a non working odometer you know there is a first worm issue in the head.
I'd also like to remind everyone to NEVER put grease, wd-40 or other types of grease (lube) on a speedo cable. The cables are reverse wound and this will pack the grease in the speedo head.. The firstworm bushing is made from oylite and the lube will cause premature failure.
If you decide to remove the speedometer, here is a great page on how to get the dash pad out of the car... the easy way.
1968-1977 Corvette Left Hand Dash Pad Removal
If the odometer is not working.. the speedometer needs to come out and be serviced.
When the first worm bushing wears out.. it puts the first worm (A) in a bind with the second worm (B). The first, second, third and fourth gears are what drive the odometer and the trip odometer. When the first worm binds with the second worm it eats the teeth off the gear. This stops the function of the odometer.
Once the bushing gets worn enough the first worm magnet will start hitting (scrapping) the speed cup... This cause erratic needle jumping and moving. The speed cup has a shaft on it that the needle attaches to and when the first worm bushing gets bad enough it will eventually grab the speed cup slamming the needle and in most cases breaking it and the speed cup.
Replacing (and they are available) the second worm gear with the plastic replacement is only a band-aide and actually a huge waste of time considering how hard it is to remove the speedometer from the car.
Other items that can cause a speedometer to be jumpy would include: Defective or binding speedometer cable, worn driven gear in the transmission, cruse control transducer(on equipped cars). The previous items can cause bouncing but anytime you have a working speedo with a non working odometer you know there is a first worm issue in the head.
I'd also like to remind everyone to NEVER put grease, wd-40 or other types of grease (lube) on a speedo cable. The cables are reverse wound and this will pack the grease in the speedo head.. The firstworm bushing is made from oylite and the lube will cause premature failure.
If you decide to remove the speedometer, here is a great page on how to get the dash pad out of the car... the easy way.
1968-1977 Corvette Left Hand Dash Pad Removal
Thread Starter
Drifting
Joined: Jul 2012
Posts: 1,255
Likes: 297
From: Slovenia, EU
2017 C3 of Year Finalist
Quite some work to be done then.
Is it meaningful then to do some other stuff while I do that?
Maybe change steering column parts? Steering coupler and so on?
Is it meaningful then to do some other stuff while I do that?
Maybe change steering column parts? Steering coupler and so on?
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,116
From: Crossville TN
Yes. If you get that far into dash disassembly, you need to carefully consider what else might be "do good" actions to take at the same time. Considerations are changing bulbs (incandescent or LED's); repairing or refurbishing the components for the wiper door (if you have one), 'ram' air door (if you have one), headlamp switch, and sealing ductwork for the A/C system; dash speaker replacement/exchange along with any audio system updating, if desired; installing electronic cruise control if desired.
And, with the left dash pad out, it's a good time to redo any gauge work and/or clock repair in the center bezel area.
If you have a copy of the A.I.M. for your car, carefully scan all the relevant drawings for those areas to see what all is in there. That will spur some thoughts on what you might want done for those components (repair/refurb/replacement/additions). Make sure to take notes as you are thinking about this stuff; otherwise you will lose train of thought and miss some opportunities.
And, with the left dash pad out, it's a good time to redo any gauge work and/or clock repair in the center bezel area.
If you have a copy of the A.I.M. for your car, carefully scan all the relevant drawings for those areas to see what all is in there. That will spur some thoughts on what you might want done for those components (repair/refurb/replacement/additions). Make sure to take notes as you are thinking about this stuff; otherwise you will lose train of thought and miss some opportunities.
Last edited by 7T1vette; Nov 1, 2016 at 04:55 AM.
Thread Starter
Drifting
Joined: Jul 2012
Posts: 1,255
Likes: 297
From: Slovenia, EU
2017 C3 of Year Finalist
Yes. If you get that far into dash disassembly, you need to carefully consider what else might be "do good" actions to take at the same time. Considerations are changing bulbs (incandescent or LED's); repairing or refurbishing the components for the wiper door (if you have one), 'ram' air door (if you have one), headlamp switch, and sealing ductwork for the A/C system; dash speaker replacement/exchange along with any audio system updating, if desired; installing electronic cruise control if desired.
And, with the left dash pad out, it's a good time to redo any gauge work and/or clock repair in the center bezel area.
If you have a copy of the A.I.M. for your car, carefully scan all the relevant drawings for those areas to see what all is in there. That will spur some thoughts on what you might want done for those components (repair/refurb/replacement/additions). Make sure to take notes as you are thinking about this stuff; otherwise you will lose train of thought and miss some opportunities.
And, with the left dash pad out, it's a good time to redo any gauge work and/or clock repair in the center bezel area.
If you have a copy of the A.I.M. for your car, carefully scan all the relevant drawings for those areas to see what all is in there. That will spur some thoughts on what you might want done for those components (repair/refurb/replacement/additions). Make sure to take notes as you are thinking about this stuff; otherwise you will lose train of thought and miss some opportunities.
I have some plans for this winter and they just might get done.
