What would cause the speedometer to be off on a 96 Chevy S-10?

* Incorrect tire size: If your tires are not the same size as the ones that were originally installed on your truck, your speedometer will be off. For example, if your truck came with 225/75R15 tires and you install 235/75R15 tires, your speedometer will read about 3.6% faster than your actual speed.

* Faulty vehicle speed sensor: The vehicle speed sensor is responsible for sending a signal to the speedometer that tells it how fast the vehicle is moving. If the vehicle speed sensor is faulty, the speedometer will not be able to receive the correct signal and will be inaccurate.

* Faulty speedometer: The speedometer itself may be faulty. If this is the case, the speedometer will not be able to display the correct speed regardless of the input it receives from the vehicle speed sensor.

* Worn speedometer cable: If your truck has a mechanical speedometer, the speedometer cable may be worn out. This can cause the speedometer to be inaccurate or jumpy.

* Odometer gear: The odometer gear may be worn or damaged. This can also cause the speedometer to be inaccurate or jumpy.