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Discussion Starter #1
IM in the process of restoring a 67 Mustang. the speedometer gear was broke in half, so I replaced it with a new Scott Drake gear. Everything seems to work fine except when I back up the odometer starts lowering the number of miles? IM not sure but I don't think this should happen. Anyone know anything about this? Bob
 

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well your speedo cable is turning backwards when you are reversing, on my spare speedo if i turn the spinner the opposite direction the numbers go down as well.

most cable driven in the trans speedo's will turn backwards if you are going in reverse.

remember Ferris Bueller's day off they tried it with the Ferarri?
 

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Good question. I know with newer vehicles in the last decade or so they won't take the milage off in reverse (even non-electronic) but back in the 60s they may have.
 

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Every 60s mechanical speedo, and many from a whole lot later, when run in reverse will decrease the odometer mileage. I have 5 cars through '89 and they all do that. Its a direct gear drive; drive it backwards and it counts backwards. The needle would also display negative MPH if it weren't for a little peg inside that prevents the needle from going below zero. Used car crooks used to spend a lot of time with a reversible drill running the mileage backwards before selling a car. If they were smart, its easier and quicker to take the speedo apart and set the odometer manually to any mileage you want. Congress in the 70s spent a lot of time trying to figure out how to keep people from turning back odometers and is the main reason for the 'I have no idea what the mileage is' statements you now have to sign to sell a car.
 

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Discussion Starter #5
Ok, well Thanks for all the help and great input. Now I wont be crawling under the car to take it all apart again. :shigrin Bob
 

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I once won a local road rally in my '68 Cougar even though I overshot one turn and had about a half mile too much odometer reading. I backed my way until the extra mileage was erased.
 
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