Component Tests and General Diagnostics
Analysis of LeakageClean up the leaking area enough to identify the exact source. An axle leak can be caused by the following:
^ Axle lubricant level is too high.
^ Worn or damaged halfshaft seals or differential seals.
^ Axle housing is cracked.
^ Flange yoke seal is worn or damaged.
^ Pinion flange is scored or damaged.
^ Axle cover is not sealed.
^ Vent is plugged.
Repair the axle as necessary. Make sure the axle lubricant is at the correct level.
Axle Vent
NOTE: If a plugged vent cannot be cleared, install a new vent.
A plugged vent will cause excessive seal lip wear due to internal pressure buildup. If a leak occurs, check the vent.
Flange Yoke Seal
Leaks at the axle drive pinion seal originate for the following reasons:
^ Seal is not correctly installed.
^ Damaged seal journal surface.
Any damage to the seal bore (dings, dents, gouges, or other imperfections) will distort the seal casing and allow leakage past the outer edge of the axle drive pinion seal.
The axle drive pinion seal can be torn, cut, or gouged if it is not installed carefully. The spring that holds the axle drive pinion seal against the pinion flange can be knocked out, which can allow leakage past the lip.
The rubber lips can occasionally become hard (like plastic) with cracks at the oil lip contact point. The contact point on the pinion flange may blacken, indicating excessive heat. Marks, nicks, gouges, or rough surface texture on the seal journal of the pinion flange will also cause leaks.
A new pinion flange must be installed if any of these conditions exist.
Metal chips or sand trapped at the sealing lip can also cause oil leaks. This can cause a wear groove on the pinion flange and heavy pinion seal wear.
When a seal leak occurs, install a new seal and check the vent.
Differential Seals
Stub shaft pilot bearing housing seals are susceptible to the same kinds of damage as axle drive pinion seals if they are incorrectly installed. The seal bore must be clean and the lip handled carefully to avoid cutting or tearing it. The seal journal surface must be free of nicks, gouges and rough surface texture.
Analysis of Vibration
Few vibration conditions are caused by the rear axle. For a vibration concern, follow the diagnosis procedure in General Information unless there is a good reason to suspect the axle.
Tires
WARNING: Do not balance the wheels and tires while they are mounted on the vehicle. Possible tire disintegration or differential failure could result, causing personal injury or extensive component damage. Use an off-vehicle wheel and tire balancer only.
Most vibration is caused by tires, driveline angle or driveline imbalance.
Vibration is a concern with modern, high-mileage tires if they are not "true" both radially and laterally. They are more susceptible to vibration around the limits of radial and lateral runout of the tire and wheel assembly. They also require more accurate balancing. Wheel and tire runout checks, truing and balancing are normally done before axle inspection.
Driveline Imbalance
Driveline imbalance can be caused by excessive looseness in the driveshaft, damaged driveshaft tubing, looseness or high runout at the driveshaft attachments. Excessive looseness in the driveshaft can be caused by CV joint or universal joint wear as well as loose fitting slip-yoke splines. Inspect and install new driveshaft components as necessary.
Axle Noise
NOTE: Before disassembling the axle to diagnose and correct gear noise, eliminate the tires, exhaust, trim items, roof racks and wheel bearings as possible causes. Follow the diagnostic procedures in General Information.
The noises described as follows usually have specific causes that can be diagnosed by observation as the unit is disassembled. The initial clues are the type of noise heard during the road test.
Gear Howl and Whine
Howling or whining of the ring gear and pinion is due to an incorrect gear pattern, gear damage or incorrect bearing preload.
Bearing Whine
Bearing whine is a high-pitched sound similar to a whistle. It is usually caused by worn damaged pinion bearings, which are operating at driveshaft speed. Bearing noise occurs at all driving speeds. This distinguishes it from gear whine which usually comes and goes as speed changes.
As noted, pinion bearings make a high-pitched, whistling noise, usually at all speeds. If however there is only one pinion bearing that is worn damaged, the noise may vary in different driving phases. New pinion bearings must not be installed unless they are scored or damaged or there is a specific pinion bearing noise. A worn damaged bearing will normally be obvious at disassembly. Examine the large end of the rollers for wear. If the pinion bearings original blend radius has worn to a sharp edge, a new pinion bearing must be installed.
A wheel bearing noise can be mistaken for a pinion bearing noise. Check the wheel bearing for a spelled cup, and spelled/damaged rollers. Install a new wheel bearing if any of these concerns are detected.
Chuckle
Chuckle that occurs on the coast driving phase is usually caused by excessive clearance between the differential gear hub and the differential case bore.
Damage to a gear tooth on the coast side can cause a noise identical to a chuckle. A very small tooth nick or ridge on the edge of a tooth can cause the noise.
Clean the gear tooth nick or ridge with a small grinding wheel. If the damaged area is larger than 3.2 mm (1/8 inch), install a new gearset.
To check the ring gear and pinion, remove as much lubricant as possible from the gears with clean solvent. Wipe the gears dry or blow them dry with compressed air. Look for scored or damaged teeth. Also look for cracks or other damage.
If either gear is scored or badly damaged, a new ring gear and pinion must be installed.
If metal has broken loose, the axle housing must be cleaned to remove particles that will cause damage. At this time, any other damaged parts in the axle housing must also be installed new.
Knock
Knock, which can occur in all driving phases, has several causes including damaged teeth or gearset.
1. NOTE: Measure the end play with a dial indicator and not by feel.
Knock is also caused by excessive end play in the axle shafts. Up to 0.762 mm (0.030 inch) is allowed in semi-float axles. The frequency of the knock will be less because the axle shaft speed is slower than the driveshaft.
Clunk
Clunk is a metallic noise heard when the automatic transmission is engaged in REVERSE or DRIVE. The noise can also occur when throttle is applied or released. It is caused by backlash somewhere in the driveline or loose suspension components; it is felt or heard in the axle.
Additionally, clunk may be heard upon initial drive-away. This occurs as engine torque shifts vehicle weight, forcing changes in driveline angles which prevent the driveshaft slip-yoke from sliding on the output shaft. To correct this condition, lubricate the slip-yoke splines.
Bearing Rumble
Bearing rumble sounds like marbles being tumbled. This condition is usually caused by a worn damaged wheel bearing. The lower pitch is because the wheel bearing turns at only about one-third the speed of the driveshaft. Wheel bearing noise also may be high-pitched, similar to gear noise, but will be evident in all four driving modes.