Anytime a transmission shows signs of a problem, such as harsh shifting or slipping, the repairs can be a minor fix. Other times the transmission will need a complete rebuild, if the problem is caused by a major defect. Whether you should replace the front pump at the same time as you perform a rebuild is determined by the condition of the connecting components.
The automatic transmission has two pumps that work with the transmission. One of those pumps is the front pump that pushes transmission fluid through the valve body. The front pump is responsible for providing all the oil pressure the transmission requires. The front shaft of the transmission works in conjunction with the front pump. If you replace the reaction shaft, you must replace the front pump. If the reaction shaft can be cleaned and reused, it is best to rebuild the old front pump and reinstall the component.
The torque converter takes the place of the clutch in an automatic transmission. It is like pressing the clutch when you stop the vehicle. The torque converter allows the vehicle to continue running while at a stop. Three different components make up the inside of a torque converter: the pump, stator and turbine. If the torque converter was not the cause for the transmission rebuild, then you can reuse the converter without replacing the pump. If you replace the torque converter, the new component will come with a pump. Lastly, if you rebuild the torque converter and decide to replace the stator or turbine, then you must replace the pump.
Every transmission rebuild must have certain parts replaced. Those parts include the filter, band or bands, bushings, washers, modulator and gaskets. A master rebuild kit will include a set of the friction clutch plates or a set of steel clutch plates, which must also be replaced in a basic transmission rebuild. Most of the time, you can reuse many of the existing transmission parts during a rebuild, including the pumps.
During a basic transmission rebuild, you may encounter problems with certain components that will require replacement. Any damaged part must be replaced, such as the sprag, bearings, solenoids and switches, torque converter -- and any other hard part. If the torque converter requires replacement, one of the pumps will automatically be replaced, as mentioned earlier. If the front pump was the cause of the transmission problems, then it will require replacement.
