It is an electric speedo so it can be the speed sensor or in the speedo itself.
If the speedo works and the odometer doesn't, it neeeds to go to the speedo shop as the problem is inside the spedo. GoodluckJoe
Actually, there is no way to repair a tear in any suit and restore its hydro-dynamics
confirm gearbox isn't overfilled! Failing this replace speedo cable.
Disconnecting the speed sensor stops the speedo and odometer. The odometer has to be changed by a certified speedo repair shop.
May have to take the car to a certified speedometer repair shop
Probably will have to change out the speedo.
More info would help here. There is a cable that runs from the back of the speedo, to the trans. There is a cable running through the outer case of the cable. The core spins, which activates the speedo head. Disconnect the cable at the trans, and spin the core with your fingers, while someone whatches the speedo. It should jump, when you spin it. No jump, bad cable, or speedo. If it jumps, then the plastic gear it connects to inside the trans, is bad. Chevy dealer has them. They are color coded according to rear gear ratios. If the speedo is bad, a speedo shop, or, a reproduction company like Classic ind., or Year 1, will help you.
Depending on what you mean by "repair", the common issue for a speedo not working in an 80s Monte, is due to a bad cable, which would just need replacing. Your question needs a little more detail.
Originally, "speed on in your speedo."
if you have changed the tires to a different size than what was factory size this will throw the speedo out if your car is computerized this can be corrected at mechanic shop if tires are not the problem and no computer, i would say it is more likely to be the speedo head or the actual speedo cable
Garret T25