Q: Mustang engine swap. The speedometer doesn't work now. Why? Mustang

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Have a mustang that my son put an engine from another car in it. The speedometer doesn't work now. What if the engine speed sensor is not the same? Will this cause the speedometer to bu out of calibration with the speed sensor? How do I remedy this problem?

Hello - the speedometer is driven by a sensor on the transmission. Perhaps this problem is because the sensor was not re-connected after the swap? If the transmission was also swapped, it is possible the sensor on the donor transmission is not compatible with the wiring and speedometer gauge on the vehicle. I would recommend an inspection of the speedometer components by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, diagnose this problem, give you an accurate assessment of damage and cost estimate for repairs.

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