Diagnostics
*Read trouble codes from the Transmission Control Module (TCM).
* Check the transmission fluid level and condition.
* Check the condition of the TCM wiring and connectors.
* Carry out a test drive to evaluate the behavior of the transmission.
Common problems and repairs
Slippage
* Replace friction discs and steel plates.
* Check the valve body for leaks and contamination.
* Replace solenoids and shift sensors.
Jerks
* Replace brake bands and friction linings.
* Clean the valve body and solenoids.
* Reprogram TCM for improved shifting.
Torque converter malfunction
* Replace the torque converter with a new or remanufactured one.
* Check the condition of the drive and turbine shafts.
* Check the condition of the pump gears and bearings.
Transmission fluid leaks
* Replace worn or damaged seals and gaskets.
* Check the integrity of the transmission housing and coolant line.
* Repair or replace the failed input shaft oil seal.
Burnt out solenoids
* Replace faulty solenoids.
* Check the wiring and solenoid connectors.
* Diagnose TCM solenoids for faults.
Valve body malfunction
* Clean or replace valve body.
* Check solenoids and sensors for leaks and binding.
* Make sure valve body hydraulic passages are clean and not blocked.
Overheat
* Check the condition of the radiator and cooling lines.
* Replace the transmission cooling thermostat.
* Troubleshoot the TCM for overheating.
Repair cost
The cost of repairing a Hyundai Sonata automatic transmission may vary depending on the problem and location of the repair. It usually ranges from $1,500 to $5,000. However, the cost can increase significantly depending on the complexity of the repair.
Recommendations
* Maintain your automatic transmission regularly, including changing the transmission fluid and filter.
* Avoid aggressive gear changes.
* Watch for any signs of transmission problems and seek professional help.
* Consider purchasing an extended warranty for your automatic transmission.