The transmission on a Pontiac Grand Prix is technically called a transaxle, though the usage of the word "transmission" is common. The transaxle combines the differential gears with the transmission in one housing, instead of two separate housings (as is done with rear-drive vehicles). The transmission in a Grand Prix is an automatic transmission and should be trouble-free for the life of the car. However, on rare occasions, gear teeth do chip or wear down to a point where the transmission will not shift properly. When this happens, it's best to replace the transmission.
Disconnect the cables running to the positive and negative battery terminals by loosening the nut on the cable clamps and sliding the clamps off the battery terminals.
Remove the nuts holding the battery tie down in place. Then remove the battery from the engine and battery tray underneath the battery.
Remove the bolts holding the air intake system in place. Remove the hose clamp connecting the intake to the throttle body. Mark and remove all electrical connections to the intake assembly using masking tape and a marker.
Remove the four bolts that hold the power distributor to the engine block on the left side of the engine. Mark the location and orientation of the spark plug wires with masking tape and marker. Pull the wires off of the distributor and remove the distributor.
Mark all hoses running to the transmission with masking tape and marker and disconnect all of the hoses.
Mark all of the electrical wiring running to the transmission with masking tape and marker. Then remove all of the electrical wires.
Detach the power and ground leads running to the starter motor and remove the upper mounting bolt from the starter motor.
Pull the cooler hoses running to the transmission and plug the hoses with a clean rag to prevent fluid leaks.
Push down on the tensioner for the throttle valve and remove the pin on the end of the throttle cable from the cable pin guide by sliding it out of the cable pin guide. Then, slide the throttle cable out of the cable guide.
Loosen the front wheel lug nuts with a tire wrench by giving them a quarter turn counterclockwise with a tire wrench.
Raise the Grand Prix onto jack stands by lifting up on the front jack point with a floor jack. The front jack point is located behind the radiator.
Continue to remove the lug nuts and pull the wheels off the wheel hub.
Remove the engine splash pan and inner fender lining that is secured by plastic rivets. Prying the rivets up with a flat head screwdriver.
Place a catch pan under the Grand Prix's transmission and remove the drain bolt by turning it counterclockwise with a socket wrench. Drain all of the oil into the catch pan.
Remove the exhaust pipe bracket and cable holder from the torque converter cover.
Remove the bolts that hold the torque converter cover in place and then remove the torque converter cover.
Disconnect the shift cable from the transmission by removing the pin holding the cable in place.
Mark the relationship of the torque converter to the driveplate with masking tape and a marker. When you reinstall this component, you'll need to have the orientation correct.
Remove the bolts holding the torque converter to the driveplate.
Remove the nut holding the radius rod to the front crossmember.
Remove the bolts holding the steering knuckle and lower control arm together. Swing the hub assembly out of the way while you pry the axle from the transmission with a screwdriver. Do not damage the seal on the transmission housing while you are doing this.
Place a block of wood under the oil pan and support the engine at the oil pan with a jack. Support the transmission with a separate jack.
Raise the jack on the transmission just enough to take the stress off the mounting bolts. Remove the bolts securing the transaxle to the engine.
Lower the transmission slowly while you pull the transmission off the engine
Install the new transmission. Installation is the reverse of removal.
