GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Cobalt 🢒 Transmission/Transaxle 🢒 Manual Transaxle - MU3 🢒 Transmission Jumps Out of Gear

Diagnostic Aids

If the transaxle 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 transaxle 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 transaxle 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 transaxle 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, and feel for the synchronizer sleeve to release form the gear, and then let up on the clutch pedal. Depress the clutch pedal and move the shift lever to engage the gear again, to ensure full travel of the shift components.

    3.

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

    4.

  4. This step inspects for the misalignment of the clutch to transaxle. Misalignment may put a bind on the input shaft, allowing for the input shaft or the mainshaft to tip.

    5.

  5. This step inspects the pilot bearing and the pilot bearing journal on the input shaft. A worn pilot bearing or input shaft may allow the input shaft to tip, causing 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 conditions:
    3. • Blockage preventing full shift lever movement
    • Excessive movement in the shift lever
    • Detent plungers engaging in the shift rails
    • Synchronizer pressure pieces on the synchronizer sleeves
    • Shift cable binding
    • Shift cable proper adjustment

Did the transaxle shift completely into all gears?

Go to Step 5

Go to Step 3

3

Remove the floor console. Refer to Front Floor Console Replacement in Instrument Panel, Gages, and Console.

Inspect for the following conditions:

    • Loose mounting
    • Foreign debris

Did you find and repair the condition?

Go to Step 11

Go to Step 4

4

Inspect for proper shift cable adjustment. Refer to Shift Cable Adjustment .

Did you find and repair the condition?

Go to Step 11

Go to Step 5

5

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

Did the transaxle shift completely into all gears?

Go to Step 6

Go to Step 9

6

Inspect the engine and/or transaxle mounts. Refer to Engine Mount Inspection in Engine Mechanical - 2.0L and Transmission Front Mount Replacement , Transmission Rear Mount Replacement or Transmission Mount Replacement - Left Side .

Did you find and repair the condition?

Go to Step 11

Go to Step 7

7

Inspect the clutch housing for loose bolts or misalignment.

Are there any loose bolts or misalignment?

Go to Step 8

Go to Step 9

8
  1. Align the housing, if required.
  2. Tighten any loose housing bolts. Refer to Fastener Tightening Specifications .

Did you find and repair the condition?

Go to Step 11

Go to Step 9

9

  1. Remove the transaxle. Refer to Transmission Replacement .
  2. Remove the clutch assembly. Refer to Clutch Pressure and Driven Plate Replacement in Clutch.
  3. Inspect the pilot bearing for being faulty.
  4. Inspect the input shaft for excessive wear at the pilot bearing.

Did you find and repair the condition?

Go to Step 11

Go to Step 10

10
  1. Disassemble the transaxle. Refer to Transmission Disassemble in Manual Transmission MU3 - Unit Repair.
  2. Inspect the following components for wear or damage:
    3. • The shift rails
    • The detent plungers and springs
    • The shift forks
    • The synchronizer sleeve and speed gear selector teeth
    • The mainshaft to input shaft bearing and journals
    • The speed gear bearings and journals
    • The speed gear axial clearance
    • The mainshaft center and rear bearings

Did you find and repair the condition?

Go to Step 11

Go to Diagnostic Aids

11

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 1