GM Service Manual Online
For 1990-2009 cars only

Diagnostic Aids

If the transmission jumps out of gear during deceleration, inspect the components that may allow for the gears or shafts to tip. If the gears or shafts tip, the synchronizer sleeve can disengage from the selector teeth on the speed gear. If the transmission jumps out of gear during acceleration, inspect the components that may not allow full engagement of the synchronizer sleeve to the selector teeth on the speed gear. Insufficient engagement of the selector teeth under torque may cause the transmission to jump out of gear.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. A static shift test is performed by shifting into all gear positions with the engine not operating. While performing the test, slowly move the shift lever. Feel for proper movement of the shift lever and transmission internal shift components.

  2. A dynamic shift test is performed by shifting into all gear positions with the engine operating. Test for the correct mesh of the synchronizers sleeve and the speed gear selector teeth. Move the shift lever to NEUTRAL and then let up on the clutch pedal. Depress the clutch pedal and move the shift lever to re-engage the gear, to ensure full travel of the shift components.

  3. This step inspects for worn or damaged transmission or engine mounts. Loose mounts may cause a shock on the transmission allowing for gear disengagement.

Step

Action

Yes

No

DEFINITION: Gear disengagement occurs during acceleration or deceleration.

1

Did you review the Symptoms - Manual Transmission, and perform the necessary inspections?

Go to Step 2

Go to Symptoms - Manual Transmission.

2

  1. Perform a static shift test.
  2. Test for the following:
  3. • Blockage preventing full shift lever movement
    • Excessive movement in the shift lever
    • Detent plungers engaging in the shift rails
    • Synchronizer sleeve movement

Did the transmission shift completely into all gears?

Go to Step 4

Go to Step 3

3

Remove the shifter and inspect for worn or faulty components. Refer to Shift Control Assembly Replacement.

Did you find and repair the condition?

Go to Step 8

Go to Step 4

4

  1. Perform a dynamic shift test on the transmission.
  2. Test for the following:
  3. • Synchronizer sleeve engagement to the speed gear selector teeth
    • Detent plungers engaging in the shift rails

Did the transmission shift completely into all gears?

Go to Step 5

Go to Step 7

5

Inspect the engine and/or transmission mounts. Refer to Transmission Mount Replacement.

Did you find and repair the condition?

Go to Step 8

Go to Step 6

6

  1. Align the housing, if required.
  2. Tighten any loose housing bolts. Refer to Transmission Replacement.

Did you find and repair the condition?

Go to Step 8

Go to Step 7

7

Replace the transmission. Refer to Transmission Replacement.

Is the replacement complete?

Go to Step 8

--

8

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 1