Automatic Transmission Car Will Not Shift Gears

Possible Causes

Low Transmission Fluid Level

One of the most common reasons why an automatic transmission will not shift gears is because the transmission fluid level is low. When the fluid level is low, the transmission cannot properly circulate the fluid and lubricate the gears. This can cause the gears to slip and not engage properly.

Dirty Transmission Fluid

Another possible cause of transmission problems is dirty transmission fluid. Over time, the transmission fluid can become contaminated with dirt, metal shavings, and other debris. This can clog the transmission filter and restrict the flow of fluid. This can also cause the gears to slip and not engage properly.

Faulty Solenoids

Solenoids are electrical components that control the flow of fluid in the transmission. If a solenoid fails, it can cause the transmission to shift erratically or not at all.

Faulty Torque Converter

The torque converter is a hydraulic component that connects the engine to the transmission. If the torque converter fails, it can cause the transmission to slip and not engage properly.

Faulty Transmission Control Module (TCM)

The TCM is the computer that controls the transmission. If the TCM fails, it can cause the transmission to shift erratically or not at all.

Troubleshooting

Check the Transmission Fluid Level

The first step in troubleshooting a transmission problem is to check the transmission fluid level. The transmission fluid level should be checked with the engine running and the transmission in park. If the fluid level is low, add fluid until it reaches the full mark on the dipstick.

Change the Transmission Fluid

If the transmission fluid is dirty, it should be changed. The transmission fluid should be changed every 30,000 to 60,000 miles.

Check the Solenoids

If the transmission is shifting erratically, it is possible that one or more of the solenoids has failed. The solenoids can be tested using a diagnostic scanner.

Check the Torque Converter

If the transmission is slipping, it is possible that the torque converter has failed. The torque converter can be tested by a transmission specialist.

Check the TCM

If the transmission is not shifting at all, it is possible that the TCM has failed. The TCM can be tested by a transmission specialist.

Repair

Repairing a transmission can be a complex and expensive process. The cost of repair will vary depending on the severity of the problem.

If the transmission fluid level is low, simply adding fluid may solve the problem. However, if the transmission fluid is dirty, it will need to be changed.

If a solenoid has failed, it will need to be replaced. Solenoids are relatively inexpensive to replace.

If the torque converter has failed, it will need to be replaced. Torque converters are more expensive to replace than solenoids.

If the TCM has failed, it will need to be replaced. TCMs are the most expensive component of the transmission to replace.

Conclusion

If your automatic transmission car is not shifting gears, it is important to have it diagnosed and repaired as soon as possible. Ignoring a transmission problem can lead to more serious damage and more expensive repairs.