When determining the condition of the rear axle by noise, you should make sure that the sound is coming from the axle
This is quite difficult to do due to the relatively high noise level of a diesel engine.
Usually, the check is carried out by the exclusion method:
1. When the car is accelerating, listen to the noise and note the speed at which it appears and disappears;
the same is done in engine braking mode without using the braking system.
Usually, rear axle noises during deceleration and acceleration occur at the same speeds;
2. When coasting and the gearshift lever is in neutral.
In this case, the main gear pinions are not loaded and do not produce noticeable noise, so if the nature of the noise coincides with the noise during acceleration of the car or engine braking, this means that its source is not the main gear.
If the nature of the noise changes, then it is quite likely that the source of the noise is the main gear pinions, or the bearings of the pinion or differential;
3. With the vehicle stationary and braked, listen to the engine running in various modes to eliminate noise caused by its operation;
- with the vehicle securely braked and the rear wheels raised, start the engine and engage fifth gear.
This will determine that the noise is indeed coming from the main gear.
Rear Axle Condition Diagnostics
Fault - Troubleshooting
Increased axle noise near the wheels
Loose wheel fastenings
Wear or damage to wheel hub bearings - Tighten wheel fastenings. Replace bearings
Increased noise when operating the rear axle
Insufficient oil level in the axle housing - Restore the oil level
Loose tightening of the pinion flange nut - Tighten the nut
Worn or misadjusted pinion bearings - Check the condition of the bearings and clearances in them, replace or adjust the bearings if necessary
Scuffs on the working surface of the teeth of the main gear gears - Replace the gears
Noise when turning, knocking when turning
Scuffs on the working surface of the satellite axles - Clean up minor roughness with sandpaper, replace parts if significantly damaged
Scuffs on the surfaces of the support washers of the half-axle gears or satellites - Minor roughness clean with sandpaper, in case of significant damage replace parts
Damaged wheel hub bearings - Replace bearings
Knock when starting the car
Increased clearance in the engagement of the main gear gears - Replace gears
Worn holes for the satellite axles - Replace the differential cup and crosspiece housing
Oil leaks
Worn or damaged pinion seal - Replace seal
Oil contamination of brake shields, drums and shoes due to wear of the hub seal - Replace seal
Loose bolts for fastening the crankcase cover or fastening the axle nuts, damage to the sealing gaskets - Tighten the fasteners or replace gaskets
Clogged breather - Clean the breather
If a metallic knock appears while the car is moving, especially in 5th gear.
This means that a tooth or several teeth have clearly fallen out in the rear axle gearbox.
This knock is transmitted throughout the transmission. It is mistakenly thought that this sound is from the gearbox.
You can also make sure if you jack up the rear wheel, start the engine and shift into gear, the knock will immediately make itself felt.
This knock is also clearly observed if the car is coasted, or when shifting from high to low gear.