Inspect the rear axle before disassembly. This will aid in determining
the type of repairs or adjustments that are necessary.
The following conditions or combination of conditions may cause rear
axle noise:
| • | The inner bearing preload of the differential drive pinion gear. |
| • | The outer bearing preload of the differential drive pinion gear. |
| • | The differential side bearing preload. |
Inspect the following before removing the differential assembly from
the axle housing. Refer to
Gear Tooth Contact Pattern Inspection
:
| • | The total differential preload. |
| • | The tooth contact pattern. |
Record and analyze these measurements before removing the differential
case from the housing.
Differential Ring Gear Tooth Nomenclature
The drive side (5) of the differential ring gear tooth is convex.
The tooth contact (4) of the differential ring gear is the center
area of the drive side (5) that makes the most physical contact with
the pinion gear. Refer to Effects Of Increasing Load On Tooth Contact Pattern.
The coast side (3) of the differential ring gear tooth is concave.
The toe end (2) of the differential ring gear tooth is the end
that is nearest to the center of the differential ring gear.
The heel end (1) of the differential ring gear tooth is the end
that is farthest away from the center of the differential ring gear. The
toe end of the tooth is smaller than the heel end.
Effects Of Increasing Load On Tooth Contact Pattern
The load on the differential ring and on the drive pinion gear is increased
during vehicle acceleration.
An increased load on the differential ring and on the drive pinion gear
may cause the tooth contact pattern to spread. Under a very heavy load,
the tooth contact may extend from the near toe to the near heel on the drive
side.
As loads increase, the following changes in the tooth contact pattern
occur:
| • | Contact moves toward the heel. |
| • | Contact area increases across the face of the gear. |
The following tooth contact pattern test recreates the effects of a
light load. For this reason, the patterns that will be obtained by the following
test will only extend to about half of their potential expansion.
Important: The contact pattern is centrally located up and down on the face of
the differential ring gear teeth.
The following conditions may cause a change in the tooth contact pattern
under a load:
| • | Insufficient preload of the drive pinion. |
| • | Insufficient preload of the differential bearings. |
Adjustments Affecting Tooth Contact
The following adjustments will affect the tooth contact pattern:
| • | An adjustment to the backlash |
| • | An adjustment to the position of the drive pinion gear (7)
in the rear axle housing |
The effects of bearing preloads are not readily apparent on hand-loaded
tooth contact pattern tests.
Use differential bearing shims (6) in order to adjust the backlash.
The shims (6) move the entire differential (5) closer to or
farther from the drive pinion gear (7).
You can also use bearing shims (2) can in order to set both the
differential bearing preload and the pinion depth (1).
| • | Make the following changes in order to increase the backlash: |
| - | Increase the thickness of the right bearings shim (6) |
| - | Decrease the thickness of the left bearing shim (3) |
| • | Make the following changes in order to decrease the backlash: |
| - | Decrease the thickness of the right bearings shim (6) |
| - | Increase the thickness of the left bearing shim (3) |
You can adjust the position of the drive pinion gear (1) by changing
the thickness of the shims (2) between the following components:
| • | The drive pinion gear head (7) |
| • | The race of the differential drive pinion gear inner bearing |
The drive pinion gear shim (2) is used in the rear axle in order
to compensate for manufacturing tolerances.
| • | Increasing the shim thickness moves the drive pinion gear (7)
closer to the centerline of the differential ring gear (4). |
| • | Decreasing shim thickness moves the drive pinion gear (7)
farther away from the centerline of the differential ring gear (4). |
Effects Of Differential Drive Pinion Gear Position On Tooth Pattern
The following tooth contact pattern exists when the differential drive
pinion gear is too far away from the ring gear centerline:
| • | High heel contact on the drive side (4) |
| • | High toe contact on the coast side (3) |
Decrease the backlash in order to move the differential drive pinion
gear closer to the ring gear centerline. This will cause the following tooth
contact pattern:
| • | Heel contact on the drive side moves down and toward the toe. |
| • | Toe contact on the coast side moves down and toward the heel. |
The following tooth contact pattern exists when the differential drive
pinion gear is too close to the ring gear centerline:
| • | Low toe contact on the drive side (4). |
| • | Low heel contact on the coast side (3). |
Increase the backlash in order to move the differential drive pinion
gear away from the ring gear centerline. This will cause the following tooth
contact pattern:
| • | Toe contact on the drive side moves up and toward the heel. |
| • | Heel contact on the coast side moves up and toward the toe. |
The following tooth contact pattern exists when the differential drive
pinion gear is properly positioned in relation the ring gear centerline:
| • | The contact pattern is centered between the heel and the toe on
the drive side of the ring gear (4). |
| • | The contact pattern is centered between the heel and the toe on
the coast side of the ring gear (3). |
