GM Service Manual Online
For 1990-2009 cars only

The Hydra-Matic 3L30 transmission is a fully automatic unit for rear wheel drive vehicles which provides three forward gear ranges and a reverse.

The major components of this transmission are:

    â€¢ Torque converter clutch assembly
    â€¢ Gear type oil pump
    â€¢ Low band assembly
    â€¢ Three multiple disc clutches
    â€¢ Planetary gear set
    â€¢ One sprag clutch
    â€¢ Valve body assembly

The oil pressure and shift points are controlled by a vacuum modulator that senses engine torque as a relation to engine vacuum.

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

    â€¢ 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.
    â€¢ R--Reverse allows the vehicle to be operated in a rearward direction.
    â€¢ N--Neutral allows the engine to be started and operated without driving the vehicle. If necessary, you may select this position in order to restart the engine with the vehicle moving.
    â€¢ D--Drive position is used for normal driving conditions. Drive position provides three gear ratios plus a converter clutch operation. Downshifts are available for safe passing by depressing the accelerator.
    â€¢ 2--Manual second provides acceleration and engine braking. You may select this range at any vehicle speed.
    â€¢ 1--Manual Low provides maximum engine braking. You may select this range at any vehicle speed.