Transmission General Description

WARNING: This page is about a different car, the 2008 Buick Lucerne. However, it is still accessible from the selected car via links, so may be relevant.

The 4T80-E is a fully automatic front wheel drive electronically controlled transmission. The 4T80-E provides four forward ranges including overdrive. The transmission control module (TCM) controls shift points by means of two shift solenoids. Three gear-type oil pumps supply the oil pressure. The TCM regulates oil pressure by means of a transmission pressure control solenoid. The TCM controls the shift schedule and the TCC apply rates. Many sensor inputs also influence the shift schedule and the TCC apply rates.

You can operate the transmission in any one of the following seven modes:

P - Park position prevents the vehicle from rolling either forward or backward. For safety reasons, use the parking brake in addition to the park position.
R - Reverse allows the vehicle to be operated in a rearward direction.
N - Neutral allows the engine to be started and operated while driving the vehicle. If necessary, you may select this position in order to restart the engine with the vehicle moving.
OD - Overdrive is used for all normal driving conditions. Overdrive provides four gear ratios plus a converter clutch operation. Depress the accelerator in order to downshift for safe passing.
D - Drive position is used for city traffic and hilly terrain. Drive provides three gear ranges. Depress the accelerator in order to downshift.
2 - Manual second provides acceleration and engine braking.
1 - Manual Lo provides maximum engine braking.