GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2004 🢒 GTO 🢒 Engine 🢒 Engine Electrical 🢒 Transmission Gear Clash When Shifting Gears

Diagnostic Aids

Gear clashing may be caused by shifting at too high of an engine RPM or by rushing the shift. If gear clashing is occurring in more than one gear, the clutch may not be releasing properly for proper synchronizer operation.

Test Description

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

  1. This step tests for the proper release of the clutch. If the clutch reserve is not correct, the mainshaft gears may be turning, causing the gear to clash.

    2.

  2. This step inspects for the proper transmission fluid. The proper fluid is required for the correct lubrication of the synchronizers.

    3.

  3. A static shift test is performed by shifting into all of the gear positions with the engine not operating. While performing the test, you should note how the shift lever movement feels. Also, while shifting from one gear to another, feel for binding in the shift rails. You should be able to feel the detent plungers operating when coming out of a gear and going into a gear. Excessive play in the gear shift lever may prevent the shift forks from fully engaging the synchronizer.

    4.

  4. A dynamic shift test is performed by shifting into all of the gear positions with the engine operating. Test for the correct mesh of the synchronizers and for the clutch releasing correctly. Move the shift lever and feel for the synchronizer sleeve to just release from the gear then let up on the clutch pedal. Depress the clutch pedal and move the shift lever to engage that gear again. If the transmission shifts back into the gear without clashing, the clutch is releasing correctly and the synchronizer is operating. If clashing occurs, test another gear. If all gears clash, the clutch is not releasing correctly.

Step

Action

Yes

No

DEFINITION: Noise from the transmission when shifting gears. A grinding or grating sound when the synchronizer sleeve is engaging with the selector teeth on the speed gear. A suspected internal transmission condition exists if the noise only happens in one gear.

1

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

Go to Step 2

Go to Symptoms - Manual Transmission

2

With the engine operating, does the transmission shift from neutral to any gear without the vehicle lurching or gear clashing?

Go to Step 5

Go to Step 3

3

Inspect for proper clutch operation. Refer to Clutch System Description and Operation in Clutch.

Does the clutch operate properly?

Go to Step 5

Go to Step 4

4

Repair the clutch system. Refer to Symptoms - Clutch in Clutch.

Did you find and repair the condition?

Go to Step 11

Go to Step 5

5

Inspect for the correct transmission fluid level and for the correct fluid. Refer to Transmission Fluid Replacement .

Is the transmission fluid level correct and at the correct level?

Go to Step 7

Go to Step 6

6

Fill the transmission to the correct level or change the fluid if it is the incorrect type.

Does the transmission still have gear clash?

Go to Step 7

Go to Step 11

7
  1. Perform a static shift test on the transmission.
  2. Test for the following conditions:
    3. • Blockage preventing full shift lever movement
    • Excessive movement in the shift lever
    • Binding in the shift lever
    • Detent plungers or shift rails binding

Did the transmission shift smoothly into the gear that is clashing?

Go to Step 9

Go to Step 8

8
  1. Remove the shift lever.
  2. Inspect for damaged or worn components. Refer to Shift Control Assembly Replacement .

Did you find and repair the condition?

Go to Step 11

Go to Step 9

9
  1. Perform a dynamic shift test on the transmission.
  2. Test for the following conditions:
    3. • Detent plungers or shift rails binding
    • Synchronizer sleeve binding
    • Gear clashing in more than the suspected gear

Is the transmission hard to shift into all gears?

Go to Transmission Shifts Hard

Go to Step 10

10
  1. Disassemble the transmission. Refer to Transmission Disassemble in the Manual Transmission Unit Repair Manual.
  2. Inspect the following transmission components for the suspect gear that is clashing:
    3. • Excessive synchronizer blocking ring to gear clearance
    • Synchronizer sleeve to hub lash or rock excessive
    • Excessive axial clearance in the speed gear
    • Mainshaft to speed gear bearing or journal worn
    • Shift fork worn or damaged
    • Internal shift control worn or damaged
    • Mainshaft bearing worn or damaged
    • Input gear bearing or pilot bearing worn

Did you find and repair the condition?

Go to Step 11

Go to Diagnostic Aids

11

Operate the system and verify the repair.

Did you correct the condition?

System OK

Go to Step 1