WTH happened with my speedo?

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sixtyorso

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1968 Road Runner. Car sat 35 years and I just got it running. Speedo needle will bounce a little bit now and then but it's getting better (yes I did install a new cable assembly) The thing that has me and several others baffled is the odometer now runs backwards as I drive forward. I'm taking miles off the car as I drive it! Anybody know why this happened? Any ideas?
 
With a thread title like that, I was afraid to look. :lmao:

I would put another gauge cluster in it. They are not that expensive and not that hard to change.
 
Well, the first thing I thought was you put the cable backwards, but honestly I never heard of a similar problem.n
 
I've read about this happening. The odometer is interchangeable between car models except for one key feature...

Chances are that someone switched out the odometer to show lower miles (like taking your car through the Peabody's wayback machine)

Here's a pic I snagged off the web... See if you can spot the difference. I'm told one is used when the odometer is above the speedometer center and one is for below the speedometer center.

7000691-DSCN4789-1.jpg

7000691-DSCN4789-1.jpg
 
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Brackets (no idea what those are called) by the gears seem to be mounted at different heights allowing for a different pinion gear...?
 
I am assume that it is mechanical. I have had some problem's in past with tractor's and motor cycle odometer's A long with car's. tore them apart to fix them the magnet bell broken and worm gear worn out for mile indicator. Some I was able to oil and clean up to work but most were just plain shot and had to replace them. Sorry that is all I know unless you take it to a speedo shop but most work with electrical one's because of new car's are that way. Hope you find the problem may be a bug in it or peace of trash. Glad she is running hope you enjoy the ride mine is going to full restoration 1969 Runner.
 
Looks to me that on the right unit the input shaft is off center to the left, while the other one is off center to the right. So assuming the input shaft rotates in the same direction on each one then each unit would rotate in different directions depending on which side it is off center.
 
Thanks for the ideas and encouragement, i'll pull the instrument cluster this winter and see what I can see.
Thanks again
 
Kind of goofy, Did this work right 35 years ago? If the speedo is working then the cable is going the right direction. Then problem has to be in the speedo head. In the above pics, they both will be the same as then numbers are backwards on the rollers....
 
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