Your automatic transmission relies on high hydraulic fluid pressure to shift gears. This pressure is produced by your transmission pump built into the front of the transmission assembly. Driven by your torque converter, it draws fluid from the oil pan and forces it through the filter and different passages inside the transmission to create high fluid pressure needed for proper lubrication and shifting.
Depending on the design of your transmission, it can be equipped with a gear-type or vane-type pump. The first one provides the same fluid flow regardless of an engine speed, while the other one can be adjusted using a special slider valve. Whichever the type, your pump is an integral part of your transmission, which is why its failure will cause a number of transmission related problems. Here are the most common of them:
If your transmission pump is not able to produce enough pressure to engage a required gear, you may experience transmission slippage and other shifting problems.
If you notice a whining noise coming from your transmission, it may be caused by a failing transmission pump. The sound should be especially noticeable at higher speeds.
Your vehicle doesn’t move
A faulty pump can’t produce enough pressure, which means your transmission can’t shift into any gear. As a result, your vehicle won’t move.
Transmission fluid leaks
This is a sign of a poor gasket between the pump and the torque converter. If you notice fluid leaks at the front of your transmission, you might have a faulty seal.
Illuminated check engine light
Your transmission control unit or powertrain control module monitors transmission operation. If it detects any problem caused by a bad pump, the computer will turn on the check engine light.
Is it possible to fix a bad transmission pump?
In case the source of the problem is a poor seal or a faulty pump, it can be fixed without an expensive transmission rebuilt if addressed quickly. If you drive with a failing pump for a long time, there is a real possibility you’ll need to replace or rebuild the transmission.
The repair cost will depend on the labor involved and the price of replacement parts. To provide you with the final calculations, your mechanic will need to test the transmission and visually inspect its parts. In many cases, the mechanic will recommend you to replace the torque converter if the transmission is rebuilt. Besides, your cooler lines should be flushed and the transmission should be refilled with fresh fluid once the repair is done.