The powertrain control module (PCM) is responsible for controlling the engine and transmission. When the PCM receives signals indicating a drop in vehicle speed and a increase in engine RPMs it takes this as a sign there is a need for a gear shift. If the PCM is damaged, it may not be able to properly control the transmission, resulting in hard shifts.
Below are other potential causes of hard shifting:
- Low transmission fluid
- Transmission solenoid or valve body failure
- Torque converter issues
- Transmission mount failure
- Faulty wiring or connectors
