Internal transmission parts may be worn or broken. Shift linkages may need adjustment or may need to be replaced. The computer or sensors may be broken.

This is most often caused by an internal problem in the transmission, which will need to be replaced or rebuilt. It may also be caused by problems with the computer, a sensor or the linkages.

Common noises are buzzes, clicks or clunks. These indicate internal problems, and the transmission will likely have to be rebuilt or replaced.

A transmission can leak in several different places. If the pan on the bottom of the transmission is leaking, it is a simple matter of replacing a gasket. If the pan has become warped, you need to replace the pan and the gasket.

If the front seal is leaking, the transmission needs to be removed from the vehicle. This seal is often called the front pump seal. When this leaks, you will notice transmission fluid dripping between the transmission and the engine. The parts are not expensive, but the actual job is very labor intensive, as the transmission must be separated from the engine to replace the front pump seal. In this case, you should have the mechanic check the clutch and the rear main seal on the engine. The cost to replace these parts isn’t too high, and you’ll save the cost of having the transmission removed again should these parts fail.

There is a seal in the tail-shaft housing where the driveshaft enters the transmission. This is an inexpensive part and repair on rear-wheel-drive vehicles. In front-wheel-drive vehicles, there is no tail-shaft housing seal. Instead, you have two axle seals, one on each side of the transmission. Because the axles must be removed, this repair is a bit more expensive than replacing a tail-shaft housing seal.

Failure to move can be caused by slippage or by a bad torque converter. Check the transmission fluid level in an automatic transmission. If it is low, the transmission will slip and the vehicle will not move. If it is full, the torque converter or the clutches could be bad.