Rear Axle Wheel Bearing Wear

TAPERED ROLLER BEARING DIAGNOSIS
Consider the following factors when diagnosing a bearing condition:
1. Note the general condition of all parts during disassembly and inspection.
2. Classify the failure with the aid of the illustrations.
3. Determine the cause.
4. Perform all repairs and follow the recommended procedures.

Abrasive Roller Wear





The pattern on the races and the rollers is caused by fine abrasives. Clean all of the parts and the housings. Inspect the seals and the bearings. Replace any leaky seals and rough or noisy bearings.

Abrasive Step Wear





The pattern on the roller ends is caused by fine abrasives. Clean all of the parts and the housings. Inspect the seals and the bearings. Replace any leaky seals and rough or noisy bearings.

Galling





Metal smears on the roller ends are caused by overheating, lubricant failure, or lubricant overload. Replace the bearing. Inspect the seals. Inspect for proper lubrication.

Etching





The bearing surfaces appear gray or grayish black in color, with related etching away of material, usually at the roller spacing. Replace the bearings. Inspect the seals. Inspect for proper lubrication.

Bent Cage





Damaged cage is caused by improper handling or improper tool usage. Replace the bearing.

Bent Cage





Damaged cage is caused by improper handling or improper tool usage, Replace the bearing.

Cage Wear





The wear around the outside diameter of the cage and the roller pockets is caused by abrasive material, Wear is caused by poor lubrication. Clean the related parts and the housings. Inspect the seals. Replace the bearings.

Indentations





Surface depressions on the race and the rollers are caused by hard particles of foreign matter. Clean all the parts and the housings. Inspect the seals. Replace the rough or noisy bearings.

Frettage





Corrosion caused by small relative movement of parts with no lubrication. Replace the bearing. Clean the related parts. Inspect the seals. Inspect for proper lubrication.

Smears





Smearing of the metal is due to slippage. Slippage may be caused by the following conditions:
- Poor fits
- Lubrication
- Overheating
- Overloads
- Handling damage

Replace the bearings. Clean the related parts. Inspect for proper fit and lubrication.

Stain Discoloration





Discoloration ranges from light brown to black. This discoloration is caused by incorrect lubrication or moisture. Reuse the bearing if you are able to remove the stains with light polishing. Reuse the bearing if there is no evidence of overheating. Inspect the seals and the related parts for damage.

Heat Discoloration





Heat discoloration ranges from faint yellow to dark blue. This discoloration results from overload or incorrect lubricant. Excessive heat causes softening of the races or the rollers. In order to check for loss of temper on the races and the rollers, perform a file test. A file drawn over a tempered part grabs and cuts the metal. A file drawn over a hard part glides readily with no metal cutting. Replace the bearings if you find overheating damage. Inspect the seals and the other related parts.

Misalignment





A misaligned outer race is due to a foreign object. Clean the related parts. Replace the bearing. Ensure that the races are properly sealed.

Cracked Inner Race





The cracked race is due to an improper fit, a cocking, or poor bearing seats. Replace the bearing. Correct the bearing seats.

Fatigue Spalling





Flaked surface metal results from fatigue. Replace the bearing. Clean all of the related parts.

Brinelling





Surface indentations in the raceway are caused by the rollers under impact loading or are caused by vibration while the bearing is not rotating. Replace a rough or noisy bearing.

REAR AXLE WHEEL BEARING WEAR DIAGNOSIS
Rear axle wheel bearing wear is described as the following conditions:

Wear (Minor)





A light pattern on races and rollers may be caused by fine abrasives. Clean all of the parts, including the housings. Inspect the seals. Replace the bearings if rough or noisy. Replace the shaft if damaged.

Wear (Major)





A heavy pattern on races and rollers may be caused by fine abrasives. Clean all of the parts including the housing. Inspect the seals. Replace the bearings if rough or noisy. Replace the shaft if damaged.

Brinelling





Surface indentations in the raceway may be caused by roll either under impact loading or vibration while the bearing is not rotating. Replace the bearing if rough or noisy. Replace the shaft if damaged.

Indentations





Surface depressions on race and rollers may be caused by hard particles of foreign material. Clean all of the parts, including the housing. Inspect the seals. Replace the bearings if rough or noisy. Replace the shaft if damaged.

Single Edge Pitting





Flaking of surface metal results from fatigue, usually at one edge of race and rollers. Replace the bearing. Clean all related parts. Replace the shaft if damaged.

Double Edge Pitting





Flaking of surface metal results from fatigue, usually at both edges of the race and rollers. Replace the bearing. Clean all related parts. Replace the shaft if damaged.

Misalignment





Outer race misalignment due to a foreign object. Replace the bearing. Ensure that the races are properly seated. Replace the shaft if the bearing operating surface is damaged.

Frettage





Corrosion set up by a small relative movement of parts with no lubrication. Replace the bearing. Clean all the relative parts. Inspect the seals. Inspect for proper fit and lubrication. Replace the shaft if damaged.

Smears





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

Knock at Low Speeds
The following two conditions may cause low-speed knock:
- Worn universal joints
- A worn and oversize side gear hub counterbore in the case
Inspect and replace the universal joints or the case and side gears as needed.

Backlash Clunk
The following conditions may cause excessive clunk during acceleration and deceleration:
- A worn rear axle pinion shaft
- A worn case
- Excessive clearance between the axle and side gear splines
- Excessive clearance between the side gear hub and the counterbore in the case
- Worn pinion and side gear teeth
- Worn thrust washers
- Excessive drive pinion and ring gear backlash

Remove the worn parts and replace as required. When possible, select close fitting parts. Adjust the pinion and the ring gear backlash.