Hummer H3. Manual — part 1461

TRANSMISSION GEAR CLASH WHEN SHIFTING GEARS

Diagnostic Aids

Gear clash may be caused by shifting at too high of an engine RPM or by rushing the shift. If gear
clash occurs 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.

2: This step tests for the proper releasing of the clutch. If the clutch reserve is not proper,
the mainshaft gears may still be turning, causing gear clash.

5: This step inspects for the proper transmission fluid. A special fluid is required for the
correct lubrication of the synchronizers.

7: 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 is felt.

10

splines worn or damaged

Synchronizer sleeve spline edges
worn or damaged

Excessive axial clearance in the
speed gear from mainshaft, speed
gear or thrust washer thrust
surfaces worn or damaged

Mainshaft to speed gear bearing
or journal worn

Shift rail and the internal shift
control lever components for
wear or damage

Shift fork worn or damaged

3. Replace worn or damaged components

as necessary.

Did you find and repair the condition?

Go to Step 10

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

2007 Hummer H3

2007 TRANSMISSION Manual Transmission - Aisin AR5 - H3

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.

9: 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 it shifts back into the gear without clashing, the clutch is releasing
correctly and the synchronizer is working. If clashing occurs, test on another gear. If all
gears clash, the clutch is not releasing correctly.

Transmission Gear Clash When Shifting Gears

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 if the noise only occurs 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 .
Does the clutch operate properly?

Go to Step 5

Go to Step 4

4

Repair the clutch system. Refer to
Symptoms - 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 the proper fluid. Refer to
Transmission Fluid Replacement.
Is the transmission fluid level correct and
at the proper level?

Go to Step 7

Go to Step 6

6

Fill the transmission fluid to the correct
level or change the transmission fluid if it

2007 Hummer H3

2007 TRANSMISSION Manual Transmission - Aisin AR5 - H3

is not the correct 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:

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

Remove the shift control housing and
inspect for damage or worn components.
Refer to Control Lever and/or Boot
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:

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

1. Disassemble the transmission. Refer

to Transmission Disassemble.

2. Inspect the following transmission

components for the gear that is
clashing:

2007 Hummer H3

2007 TRANSMISSION Manual Transmission - Aisin AR5 - H3

TRANSMISSION NOISY

Test Description

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

2: This step inspects for vibration causing a noise. If the vehicle is equipped with an
aftermarket box or is carrying a certain load, the driveline axle may not be correct and
could cause a vibration. The vibration maybe resonating into the transmission, causing a
noise.

6: This step inspects for the correct transmission fluid level. If the transmission fluid level is
excessively low, damage may have occurred to the transmission components.

10

Excessive synchronizer
blocking ring to gear clearance

Synchronizer sleeve to hub
clearance excessive

Synchronizer sleeve spline
edges worn or damaged

Excessive axial clearance in the
speed gear from mainshaft and
speed gear thrust surfaces worn
or damaged

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

Countershaft bearings worn or
damaged

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

2007 Hummer H3

2007 TRANSMISSION Manual Transmission - Aisin AR5 - H3