Analysis of Leakage
Driveline System
Analysis of Leakage
Clean 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 axle shaft seals or differential seals.
- Differential 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. Refer to Specifications.
Axle Vent
NOTE: If a plugged vent cannot be cleared, install a new vent.
A plugged vent or vent hose will cause excessive seal lip wear due to internal pressure buildup. If a leak occurs, check the vent and the vent hose. Remove the hose from the vent nipple and clear the hose of any foreign material. While the hose is removed, pass a length of mechanic's wire or a small diameter Allen wrench in and out of the vent to clean it. Connect the hose when done.
Flange Yoke Seal
Leaks at the axle drive pinion seal originate for the following reasons:
- Seal was installed incorrectly.
- Poor quality 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 rubber lips can occasionally become hard and crack at the oil lip contact point. The contact point on the pinion flange may blacken. Marks, nicks, gouges or rough surface texture on the seal journal of the pinion flange will also cause leaks.
Install a new pinion flange if any of these conditions exist.
When a seal leak occurs, install a new seal and check the vent and the vent hose to verify that they are clean and free of foreign material.
Wheel Hub Oil Seals
Wheel hub oil seals are susceptible to the same kinds of damage as axle drive pinion seals if installed incorrectly. The seal bore must be clean and the lip handled carefully to avoid cutting or tearing it. Spindle journal surface must be free of nicks, gouges and rough surface texture. For information on wheel hub oil seals, refer to Wheel Hubs and Bearings - Full Floating Axle - Dana Wheel Hubs and Bearings - Full Floating Axle - Dana or Wheel Hubs and Bearings - Full Floating Axle - Ford Wheel Hubs and Bearings - Full Floating Axle - Ford.
Axle Noise
NOTE: Before disassembling the axle to diagnose and correct gear noise, eliminate the tires, exhaust, trim items, axle shafts and wheel bearings as possible causes. Follow the diagnostic procedures in Noise, Vibration and Harshness Symptom Related Diagnostic Procedures.
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 differential 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. Do not install new pinion bearings unless bearings 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, install a new pinion bearing.
NOTE: A low-pitched rumble normally associated with a worn/damaged wheel bearing can be caused by the exterior luggage rack or tires.
A wheel bearing noise can be mistaken for a pinion bearing noise. Check the wheel bearing for a spalled cup, and spalled/damaged rollers. Install a new wheel bearing and cup 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 in), install a new gearset.
To check the differential 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 damaged badly, install a new differential ring gear and pinion.
If metal has broken loose, the differential housing must be cleaned to remove particles that will cause damage. At this time, any other damaged parts in the differential housing must also be discarded and new parts installed.
Knock
Knock, which can occur on all driving phases, has several causes including damaged teeth or gearset.
A gear tooth damaged on the drive side is a common cause of the knock. This can usually be corrected by grinding the damaged area.
Clunk
Clunk is a metallic noise heard when the automatic transmission is engaged in REVERSE or DRIVE. The noise may 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. Refer to Total Backlash Check.
Additionally, clunk may be heard upon initial drive-away. This occurs as engine torque shifts vehicle weight, forcing changes in driveline angles, preventing the driveshaft slip-yoke from sliding on the output shaft. To correct this condition, lubricate the slip-yoke splines. Refer to Driveshaft Diagrams.
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 of the driveshaft speed. Wheel bearing noise also may be high-pitched, similar to gear noise, but will be evident in all 4 driving modes.
Total Backlash Check
1. With the vehicle in NEUTRAL, position it on a hoist. Refer to Jacking and Lifting Service and Repair.
2. Remove the driveshaft. Refer to Driveshaft Diagrams.
3. Install the Drive Pinion Flange Holding Fixture.
- Clamp a rigid bar or pipe to the tool. Clamp the other end of the bar or pipe to the frame or a body member in order to prevent movement of the pinion flange.
4. Lower the vehicle so that one rear wheel is resting on a wheel chock to prevent it from turning. The other rear wheel will be used to measure total rear axle backlash.
5. Rotate the free wheel slowly, by hand, until the feeling of driving the rear axle is encountered. Place a mark on the side of the tire, 305 mm (12 in) from the center of the wheel, with a crayon or chalk.
6. While holding the crayon or chalk against the tire, rotate the wheel slowly in the opposite direction until the feeling of driving the rear axle is encountered again.
7. Measure the length of the crayon or chalk mark on the tire.
- If the length of the mark is 25.4 mm (1 in) or less, the rear axle backlash is within allowable limits.
- If the chalk mark is greater than 25.4 mm (1 in), check for these conditions:
- Elongation of the differential pinion shaft and holes in the differential case.
- Missing differential pinion thrust washer or differential side gear thrust washer.
- Galling of the differential pinion shaft and bore.
- Excessive ring gear and pinion backlash. Follow the procedure for the type of rear axle to check backlash.