Possible reasons why the automatic transmission stalls after replacing the engine:
1. Incorrect connection or damaged wiring:
* Make sure that the wiring connecting the automatic transmission to the engine and transmission control module (TCM) is connected correctly and is not damaged.
* Check for loose or damaged contacts.
2. Problems with the transmission control module (TCM):
* The TCM may be reprogrammed or damaged when the engine is replaced.
*Make sure the TCM is properly installed and flashed to work properly with the new engine.
3. Problems with sensors:
*Sensors such as the speed sensor, throttle position sensor and pressure sensor may be damaged or incorrectly connected.
* Check the sensors to ensure they are securely attached and not damaged.
4. Problems with the torque converter:
* The torque converter may be damaged or incorrectly installed during engine replacement.
* Check that the torque converter is installed correctly and does not interfere with other components.
5. Transmission fluid leaks:
*Transmission fluid leaks can cause problems with automatic transmission operation.
* Check the vehicle for leaks and repair them if necessary.
6. Wrong gearbox oil:
* The automatic transmission may be filled with the wrong type or amount of oil.
* Drain the old oil and refill with the correct type and volume specified in the owner’s manual.
7. Malfunction of the engine itself:
* Even though the engine has been replaced, it may still have problems that affect the operation of the automatic transmission.
* Check the engine for other problems that may be causing sluggishness.
Recommended actions:
* Scan the vehicle for trouble codes that may indicate a specific cause.
* Check wiring, sensors and torque converter.
*Consult a qualified mechanic for further diagnosis and repair.