GM Service Manual Online
For 1990-2009 cars only

The Reverse (R) position allows the vehicle to be operated in a rearward position.

O/D

Overdrive (in the D position with the overdrive switch pressed) is used for all normal driving conditions. It provides four gear ratios plus the Torque Converter Clutch (TCC) operation. Downshifts are available for safe passing by pressing the accelerator pedal. The PCM delays the engagement of the 4th gear (Overdrive) and the lock-up of the TCC until the engine coolant has reached an operating temperature of 55°C (131°F).

Drive

The Drive position is used for city traffic and hilly terrain. It provides three gear ratios, with available downshifts for safe passing, by pressing the accelerator pedal.

2ND

Manual 2nd is used to provide acceleration and engine braking. This range should be selected only when the vehicle speed is below 48km/h (30mph).

Low

Manual low is used to provide maximum engine braking. This range should be selected only when the vehicle speed is below 24km/h (15mph).