The reason why the automatic transmission only goes backwards and not forwards may be due to various factors:
Mechanical problems:
*Damaged input or output shaft: This may prevent power from being transferred to the forward gears.
* Stripped or broken gear teeth: This can result in a lack of mesh between the gears needed for forward movement.
* Damaged torque converter: A faulty torque converter may not provide enough oil pressure to engage forward gears.
Electrical problems:
* Faulty Shift Solenoid: The solenoid that controls the forward gears may be faulty or have a wiring problem.
* Damaged Transmission Control Module (TCM): The TCM may be faulty in sending signals to the shift solenoids, resulting in a lack of forward gears.
Hydraulic problems:
*Low Automatic Transmission Fluid Level: Too low a fluid level may cause insufficient hydraulic pressure to engage forward gears.
* Clogged Transmission Filter: A clogged transmission filter can restrict transmission fluid flow, which also results in low hydraulic pressure.
*Faulty Oil Pump: A faulty oil pump cannot provide enough fluid pressure to operate the transmission.
Other possible reasons:
*Faulty Speed Sensor: A faulty speed sensor may provide incorrect data to the TCM, resulting in incorrect gear shifting.
* Damaged wiring: Damaged wiring can interfere with communication between the TCM and the shift solenoids.
*Software Issues: Issues with the TCM software may cause transmission to shift poorly.
To determine the exact cause, it is recommended that you have the automatic transmission diagnosed and repaired by a qualified mechanic.