Hummer H3. Manual — part 984

Fig. 15: Identifying Smears
Courtesy of GENERAL MOTORS CORP.

Smearing of metal due to slippage. Slippage can be caused by poor fits, lack of lubrication,
overheating, overloads or handling damage. Replace the bearing. Clean all the related parts.
Check for proper fit and lubrication.

REAR AXLE LUBRICANT LEAK DIAGNOSIS

Rear axle lubricant leaks can occur at the following locations:

Axle tube to differential carrier housing joint

2007 Hummer H3

2007 Driveline/Axle Rear Drive Axle - H3

Axle shaft oil seal

Axle housing porosity

Differential housing cover gasket

Drain plug

Fill plug

Pinion yoke oil seal

Vent tube

Determining the Cause

While most rear axle leaks may be easy to find, determining the cause may not be. A thorough
inspection of the area around the leak may assist in determining the cause of the leak.

Oil Seals

Lubricant leaks from a oil seal may be caused by any of the following:

An improperly installed seal

A distorted seal

A worn seal

A worn shaft

A brittle seal lip

A hardened seal lip

To determine the actual cause of the leak, clean the area around the leak. Observe the area of the
leak and determine the if the seal or another component is causing the leak. A worn seal surface
will cause a leak at the sealing lip while a misaligned seal or a seal installed into a housing with
an excessive bore will cause the seal to leak at the outside surface of the seal. Hardened or
cracked seal lips usually indicate the axle is operating beyond the normal temperature limits for
the axle. A seal whose sealing surface has been nicked or cut may indicate that the shaft has a
rough, burred or gouged surface and will need to be inspected before the seal can be replaced.

Gaskets

A leak at a gasket is usually caused by a poor fit of the components on each side of the gasket
surface. Inspect each component for distortion and for nicks or gouges that may prohibit the
gasket from sealing properly.

Rear Axle Housing

2007 Hummer H3

2007 Driveline/Axle Rear Drive Axle - H3

Rear axle housing lubricant leaks usually occur at the following locations:

Drain Plug

Fill Plug

Drain and fill plug leaks are usually caused by a loose plug. These leaks can by repaired by either
tightening the plug or by using an approved sealer on the threads on the plug.

Other leaks such as axle tube to differential carrier housing or porosity leaks require the
replacement of the rear axle housing.

LOCKING DIFFERENTIAL DIAGNOSIS

1. Block the right front and rear wheels.

2. Turn the Ignition ON - Do not start the engine.

3. Place the transmission in NEUTRAL.

4. Shift the transfer case into 4 LOW.

5. Engage the differential lock switch.

6. Raise the left front wheel off the ground. Refer to Lifting and Jacking the Vehicle .

Support the left front wheel with safety stands.

7. Raise the left rear wheel off the ground. Refer to Lifting and Jacking the Vehicle .

Support the left rear wheel with safety stands.

8. Attempt to rotate the left rear wheel 1 full revolution clockwise and counterclockwise by

hand.

If the wheel does not rotate 1 full revolution in either direction, the locking
differential is engaging properly.

If the wheel rotates more than 1 revolution in either direction, the locking differential
is not engaging properly.

9. Disengage the differential lock switch.

10. Attempt to rotate the left rear wheel 1 full revolution clockwise and counterclockwise by

hand.

If the wheel rotates 1 full revolution in either direction, the locking differential is
disengaging properly.

If the wheel does not rotate more than 1 revolution in either direction, the locking

2007 Hummer H3

2007 Driveline/Axle Rear Drive Axle - H3

differential is not disengaging properly.

11. If the locking differential is not functioning properly, remove the differential and determine

the cause of failure. Refer to Differential Replacement and Locking Differential
Disassemble.

ELECTRONIC REAR DIFFERENTIAL LOCK WILL NOT ENGAGE

Circuit Description

The rear differential control circuit consists of an actuator which engages and disengages the rear
axle differential lock. The rear differential actuator consists of a coil assembly and a locking
assembly with springs and pins to lock the rear differential, all within the rear differential
assembly.

The rear axle differential lock actuator consists of the following circuits:

The rear differential lock control circuit, which is connected to the transfer case shift
control module and supplies battery voltage.

The rear differential lock return ground circuit, which is also connected to the transfer case
shift control module.

Whenever the rear differential lock has been requested the transfer case shift control module
provides battery voltage through the rear differential lock control circuit and provides ground
through the rear differential lock return circuit through a current limiting driver.

Whenever a rear differential lock is requested the transfer case must be in 4LO and the vehicle
speed must be below 5 km/h (3 mph) for the request to be accepted. The rear differential lock
will remain locked up to 32 km/h (20 mph) after which the rear differential lock will disengage.

Test Description

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

2: This step determines if the fault is present or intermittent.

3: This step determines if the transfer case shift control module is receiving a differential
lock request from the transfer case shift control switch.

4: This step determines if a bad switch is causing the symptom.

5: This step determines if a short, open or high resistance in the 5-volt reference or switch
signal circuits is causing the symptom.

6: This step determines of the coil has excessive resistance or if the windings are shorted

2007 Hummer H3

2007 Driveline/Axle Rear Drive Axle - H3