GM Service Manual Online
For 1990-2009 cars only

Condition

Action

DEFINITION: Harsh forced downshift felt when accelerating

Input speed sensor (76)

    • Perform electrical function test on the input speed sensor (76).
    • Replace the input speed sensor (76) if fails electrical function test.

Battery voltage

    • Inspect battery for correct voltage.
    • Repair charging system or replace battery.

Engine or transmission mounts

    • Inspect the engine mounts and the transmission mounts for wear or loose mounting fasteners.
    • Replace any faulty engine or transmission mounts or loose fasteners.

Suspension system

    • Inspect suspension components.
    • Replace faulty suspension components.

Transmission oil temperature sensor (32)

    • Perform function test on the transmission oil temperature sensor (32).
    • Replace the automatic transmission wiring harness assembly (78).

Line pressure control solenoid valve assembly (SLT) (312)

    • Perform electrical function checks on the line pressure control solenoid valve assembly circuit.
    • Perform electrical function check on the line pressure control solenoid valve assembly (312).
    • Replace valve body assembly (39) if line pressure control solenoid valve assembly (312) is faulty.

Transmission control module (TCM)

    • Perform function test on the TCM.
    • Replace TCM if fails function test.

Valve body (39)

Replace valve body (39).

Internal transmission parts

    • Disassemble the transmission and inspect for the following:
       - Missing retaining rings
       - Worn or broken thrust needle bearings and thrust washers
       - Differential assembly backlash
       - Worn drive and driven gears
       - Worn planetary gear assemblies
    • Replace the transmission if any faulty parts.