General diagnostics
Visual inspection / physical control
- Inspect aftermarket equipment that may affect the operation of the vehicle.
- Inspect easily accessible and visible parts of the system for obvious signs of damage or conditions that could lead to a malfunction.
- Check the correct lubricant level and viscosity.
- Determine the exact operating conditions under which complaints occur. Pay attention to factors such as speed, road conditions, ambient temperature and other features.
- Compare driving characteristics or sounds, if any, with a known serviceable vehicle and ensure that there is no attempt to correct the normal condition.
Note: Do not apply the parking brake for more than 5 seconds. This may damage the RDM.
To check the inclusion and operation of the rear axle, you can hang out four wheels, start the car and select the driving position. With proper operation of the rear axle and transfer case, all four wheels rotate at the same frequency. When the parking brake is fully applied, the rear wheels stop rotating. Press the pedal "gas", while watching the rear wheels. They will begin to rotate slightly as the drive from the engine to the drive wheels unwinds. This indicates the functioning of the AWD all-wheel drive.
The following factors may contribute to the fact that the rear axle does not work:
- Low transmission oil level
- Miniature spare or mismatched tires
- Fluid overheating condition
- Malfunction of the back bridge assy
- Transfer box not working
- Wrong fluid type
Intermittent malfunctions; Intermittent trouble codes
Test the vehicle under the same conditions reported by the customer to ensure that the system is working properly.
Noise acceptability
A gear driven unit always produces a certain level of noise. At certain speeds or different driving conditions, such as fresh tarmac, some noise is audible and acceptable. Weak noise does not harm the operation of the bridge and is considered normal.
List of symptoms (rear drive axle)
To perform symptom diagnosis, refer to the following list of symptom diagnosis procedures:
- Increased noise while driving
- Increased noise when coasting
- Unstable noise
- constant noise
- Increased noise when cornering
- Diagnosis of leakage of rear axle lubrication
Increased noise while driving
Cause
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Remedy
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Verify proper transmission oil levels before running system diagnostics.
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Weak propeller shaft mounting bolts
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Tighten screws if necessary.
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Wear of the hinge of equal angular speeds of the cardan shaft
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Replace driveshaft assembly.
Wear on the CV joint of the driveshaft can lead to noise such as clicking, rubbing or crunching.
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Wear of the hinges of equal angular velocities of the axle shaft of the wheel drive
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If necessary, replace/repair the wheel drive axle shaft. Wear on the wheel drive axle joint can cause noise such as clicking, rubbing, or crunching.
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Worn or damaged differential housing bushings (side)
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Replace bushings if necessary.
Bushing wear can cause a thud-type noise when accelerating or decelerating.
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Worn or damaged differential housing bushings (behind)
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Replace bushings if necessary.
Bushing wear can cause a thud-type noise when accelerating or decelerating.
Check bushing orientation; the adjustment slots must be in the correct position.
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Weak fastening of bolts of fastening of a back bracket of a suspension bracket
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Tighten bracket mounting bolts if necessary.
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Loose or damaged propeller shaft seal
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Repair or replace if necessary.
A loose dust shield may cause it to come into contact with the propeller shaft assembly and generate noise such as scraping or rubbing.
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Howling noise of the gearbox in the clutch assembly
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Howling type noise increases or decreases depending on vehicle speed (approximately 80-90 km/h (50-56 mph)).
Check if the fluid level is correct.
Repair or replace the unit if necessary.
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Closing shutters or groaning at low speeds or slow turns
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Noise such as slamming shutters or groaning when making slow, tight turns.
Possible contamination of the RDM due to the wrong type of fluid/water.
Replace fluid; top up if necessary and repeat the test under the same conditions.
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Increased noise when coasting
Cause
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Remedy
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Verify proper transmission oil levels before running system diagnostics.
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Weak propeller shaft mounting bolts
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Tighten screws if necessary.
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Wear of the joint of equal angular speeds of the cardan shaft.
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Replace driveshaft assembly. Wear on the CV joint of the driveshaft can lead to noise such as clicking, rubbing or crunching.
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Wear of universal joints
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If necessary, replace the cardan shaft assembly. Wear on the universal joint can lead to noise such as clicking or crunching.
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Wear or damage to the mounting bushings of the differential housing support (side)
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Check the position of the bushings and replace them if necessary. Incorrect orientation or bushing wear can cause a thud-type noise when accelerating or decelerating.
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Wear or damage to the mounting bushings of the differential housing support (behind)
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Replace bushings if necessary. Bushing wear can cause a thud-type noise when accelerating or decelerating.
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Weak fastening of bolts of fastening of a back bracket of a suspension bracket
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Tighten bracket mounting bolts if necessary.
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Loose or damaged propeller shaft seal
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Repair or replace if necessary. A loose dust shield may cause it to come into contact with the propeller shaft assembly and generate noise such as scraping or rubbing.
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Bearing noise in RDM
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Noise such as rubbing or hum increases or decreases depending on vehicle speed.
Check if the fluid level is correct. If necessary, if the noise persists, repair or replace the unit.
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Howling gearbox noise in RDM due to incorrect gear clearance
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The howling type noise increases or decreases depending on the speed of the vehicle.
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Unstable noise
Cause
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Remedy
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Verify proper transmission oil levels before running system diagnostics.
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Low gear oil levels
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Top up the bridge to the recommended level. A low level can cause intermittent or incomplete clutch pack engagement.
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Wrong gear oil
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Change gear oil, GM P/N: 9986115. Incorrect gear oil can result in a clutch pack not engaging properly or in a slipping condition.
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Deterioration of the clutch pack oil pump
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Replace clutch assembly.
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Wear of the friction discs of the clutch pack
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Replace clutch assembly.
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Constant noise
Cause
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Remedy
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Verify proper transmission oil levels before running system diagnostics.
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Low gear oil levels
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A bad seal or other types of leaks can contribute to below normal fluid levels. Add gear oil to the correct level, GM part number: 9986115.
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Wear of the constant velocity joint or universal joint of the cardan shaft
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If the CV joint is damaged, replace the propeller shaft.
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Bearing noise in clutch assembly
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This type of noise decreases or increases depending on the speed of the vehicle.
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Howling gearbox noise in RDM due to incorrect gear clearance
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The howling type noise increases or decreases depending on the speed of the vehicle.
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Increased noise when cornering
Cause
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Remedy
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Verify proper transmission oil levels before running system diagnostics. Drive a car, making turns in tight rings, both to the left and to the right. Noise complaints such as groaning, squeaking, hesitation, or pulsing may indicate a pump or clutch pack problem in the axle assembly.
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Worn or loose rear axle suspension bolts
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Repair or replace if necessary.
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Wear of the hinges of equal angular velocities of the axle shaft of the wheel drive
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If necessary, replace the wheel drive axle.
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Wheel bearing wear
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Replace wheel bearings if necessary.
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Wrong gear oil
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Change gear oil, GM part number: 9986115.
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Wear of the side and/or intermediate gears of the differential and wear of the spider
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If necessary, replace the differential cup assembly.
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Diagnosis of leakage of rear axle lubrication
Cause
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Remedy
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Clogged or damaged vent tube assembly
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If necessary, replace the ventilation tube.
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Leaking filler or drain plugs
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Apply sealant, GM part number: 12346004 (catalog number for Canada: 10953480), or equivalent on the plug threads and tighten.
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Inlet flange seal leak
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Leakage of crankcase sealing surfaces
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If necessary, dismantle the bridge and repeat the sealing of the sealing surfaces - only the clutch drum covers.
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Wear or damage to the wheel drive shaft seals
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If necessary, replace the wheel drive shaft seals.
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List of symptoms (cardan shaft)
To perform symptom diagnosis, refer to the following list of symptom diagnosis procedures:
- High frequency and normal vibration
- Clunking, popping or clicking sound
- Knocking or dull metallic sound
- Scraping sound
- Creak
- Jitter when accelerating at low speed
High frequency and normal vibration
Cause
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Remedy
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High-frequency or normal vibration occurs when the car is moving at different speeds.
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Bent or dented propeller shaft
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Replace cardan shaft.
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Primer coating on cardan shaft
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Wear of universal joints
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Replace the driveshaft assembly because the universal joint is not serviceable.
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Vibration of the drive from the engine to the drive wheels at a speed of 80 km / h (50 mph)
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Check for driveshaft runout.
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Clunking, popping or clicking sound
Cause
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Remedy
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A dull thud, pop or click is usually heard under initial load after the transmission is engaged in forward or reverse gear.
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Weak fastening of bushing bolts of the upper and lower suspension arms.
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Tighten the bolts to the specified torque.
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Weak fixed yoke or bolted flange connection
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Worn or damaged universal joint
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Replace the driveshaft assembly because the universal joint is not serviceable.
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Vibration of the drive from the engine to the drive wheels at a speed of 80 km / h (50 mph)
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Check for driveshaft runout.
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Knocking or dull metallic sound
Cause
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Remedy
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Knocking or dull metallic sound occurs when the vehicle is moving in high gear or coasting in neutral at a speed of 16 km / h (10 mph).
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Worn or damaged universal joint
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Replace the driveshaft assembly because the universal joint is not serviceable.
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Scraping sound
Cause
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Remedy
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The scraping sound occurs when the vehicle is moving at different speeds.
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Friction of toothed flange or center bearing.
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Eliminate jamming.
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Creak
Cause
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Remedy
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The creaking occurs when the car is moving at different speeds.
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Lack of lubrication
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If necessary, replace the cardan shaft assembly.
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Jitter when accelerating at low speed
Cause
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Remedy
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Shaking occurs when the vehicle accelerates at low speed.
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Weak or missing flange bolts
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Replace and/or tighten bolts to specified torque.
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Universal joint wear
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Replace the driveshaft assembly because the universal joint is not serviceable.
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