Differential Assembly: Testing and Inspection
GEAR TOOTH CONTACT PATTERN INSPECTION^ TOOLS REQUIRED
- J44856 Alignment Disc
- J44857 Side Bearing Preload Shim Selector
- J44865 Splint Socket
Before final assembly of the differential, perform a gear tooth pattern inspection.
This contact pattern inspection is not a substitute for adjusting the pinion depth and backlash. Use this method in order to verify the correct running position of the ring gear and drive pinion. Gear sets that are not positioned properly may be noisy, have a short life, or both. A pattern inspection ensures the best contact between the ring gear and the drive pinion for low noise and long life.
Gear Tooth Nomenclature
The side of the ring gear tooth that curves outward, or is convex, is the drive side (4). The concave side is the coast side (3). The end of the tooth nearest the center of the ring gear is the toe end (2). The end of tooth farthest away from the center is the heel end (1).
1. Apply pattern inspection chemical GM P/N 1052351 to all of the teeth of the ring gear.
2. Install the dial indicator on the cover at the top of the bearing bore. Preload indicator and zero it out.
3. Install the Housing Spreader J44868 on the cover.
4. Spread the cover while measuring the movement. Do not spread the cover more than 0.30 - 0.40 mm (0.012 - 0.016 inch).
5. After the spread is reached, remove the dial indicator.
IMPORTANT: Do not apply sealer to the housing or cover at this time.
6. Install the cover.
7. If a spread cover will not go over the shims and bearings, use a C-clamp and Alignment Disc J44856. Tighten the C-clamp on disc, this will straighten out the shims and bearing races.
8. Install the 4 (M8) cover bolts and tighten in a criss-cross pattern.
Torque:
Cover Bolts: 23 Nm (17 ft. lbs.)
9. Remove the Housing Spreader J44868.
10. Install 4 (M10) cover bolts and tighten in a criss-cross pattern.
Torque:
Cover Bolts: 40 Nm (30 ft. lbs.)
11. Use Spline Socket J44865 and a breaker bar over the pinion shaft.
Axle payload must be applied to the gear set to perform proper pattern inspection.
12. Install an axle shaft into differential bore.
13. Hold axle shaft with a gloved hand applying pressure while turning the pinion shaft 6 times clockwise direction and 6 times counterclockwise direction.
14. Remove axle shaft.
15. Install Alignment Disc J44856-7 into one side of the differential axle bore and tighten the nut to lock the tool in place.
16. Attach the dial indicator to the housing. Measure from the line marked on the Side Bearing Preload Shim Selector J44857. Zero out the dial indicator.
17. Install Alignment Disc J44856-8 in the opposite side axle bole.
18. Use a speed handle to rotate the differential back and forth to measure the backlash. The backlash should be 0.125 - 0.225 mm (4.92 - 8.86 inch).
NOTICE: Use the pry points only. Do not pry on sealing surface.
IMPORTANT: The rear differential may come out with the cover.
19. Remove rear cover bolts.
20. Remove the cover.
21. Observe the pattern on the ring gear teeth. Compare the pattern with the following illustrations. Use the legend below:
21.1 (1) Toe
21.2 (2) Heel
21.3 (3) Coast Side, Concave
21.4 (4) Drive Side, Convex
Condition
^ The backlash is correct.
^ The pinion depth is incorrect. The pinion gear is too far away from the gear.
Correction
Increase the thickness of the pinion shim.
Service Hints
How to inspect the pattern:
1. Brush gear marking compound on the ring gear teeth.
2. Rotate the pinion clockwise 6 times.
3. Rotate the pinion counterclockwise 6 times.
4. Observe the tooth contact pattern. Make any necessary corrections.
Condition
^ The backlash is correct.
^ The pinion depth is correct.
Correction
Correction may not be necessary
Service Hints
Loose bearings on the pinion or in the differential case may cause patterns that vary. Inspect the following preload settings:
^ Total assembly
^ Differential case
^ Pinion
If these settings are correct, look for damage or incorrectly assembled parts.
Condition
^ The backlash is correct.
^ The pinion depth is incorrect.
Correction
Decrease the thickness of the pinion shim.
Service Hints
The shims which adjust the pinion depth are located between the inner pinion bearing and the head of the pinion gear.
Adjustments Affecting Tooth Contact
There are two adjustments that affect the tooth contact pattern; backlash and drive pinion depth. The effects of bearing preloads are not readily apparent on hand loaded tooth contact pattern tests. However, bearing preloads should be within specifications before proceeding with backlash and drive pinion adjustments.
Adjust the position of the drive pinion by increasing or decreasing the distance between pinion head and centerline of the ring gear. Decreasing the distance moves the pinion closer to the centerline of the ring gear. Increasing the distance moves the pinion farther away from the centerline of the ring gear.
Adjust the backlash by means of the side bearing adjusting shims which move the case and ring gear assembly closer to, or farther from, the drive pinion. Also use the adjusting shims to set the side bearing preload.
If the thickness of the right shim is increased, along with an equal decrease in thickness of the left shim, backlash will increase.
If the thickness of the left shim is increased, along with an equal decrease in the thickness of the right shim, the backlash will decrease.