Differential Bearing Preload and Ring Gear Backlash

Differential Case Assembly into Housing

Condition 1

Follow this procedure only when gearset replacement is required and the differential bearings and the differential case do not require replacement.

1. Remove differential caps and bolts. Identify RH cap, RH cup and shim spacer to keep these components as RH and LH sets.

2. Remove differential case subassembly using the pry bar method. Reasonable effort will be required to remove subassembly if preload is within specification range. If subassembly can be removed by hand, use Condition 2 for assembly.

3. Replace ring and pinion members utilizing differential shim components from original assembly and select the hypoid pinion shim as outlined. (Shims may be reused with the exception of pinion shim which will require regauging and certification before reassembly.)

Condition 2

Follow this procedure when original differential shims are not available or when axle housing, differential case or differential bearing replacement is required.

1. With pinion depth set, and pinion installed, place the differential case/gear subassembly with bearings and cups in carrier.
   
   
   
   

2. Install a 0.265-inch shim on the LH side.
   
   
   
   

3. Install LH bearing cap finger-tight.
   
   
   
   

4. Install progressively larger shims on the RH side until the largest shim selected can be assembled with a slight drag feel.
   
   
   
   

5. Install RH side bearing cap and tighten differential bearing cap bolts to 95-115 Nm (70-85 lb-ft).
   
   
   
   

6. Rotate assembly to ensure free operation.
   
   
   
   

7. Check ring gear and pinion backlash. If backlash is within specification, Go to Step 14. If backlash is not within specification, Go to Step 10. If zero backlash is measured, proceed with Step 8.
   
   
   
   

8. If a zero backlash condition occurs, add 0.50mm (0.020 inch) to the RH side and subtract 0.50mm (0.020 inch) from the LH side to allow backlash indication.
   
   
   
   

9. Check backlash as outlined in Step 7.

10. If backlash is not to specification, correct backlash by increasing thickness of one shim and decreasing thickness on the other shim by the same amount. Refer to the following illustration for approximate shim change.
    
    
    
    

    Refer to the following chart for specific shim thicknesses.
    
    
    
    

11. Install shim and bearing caps. Tighten caps to 95-115 Nm (70-85 lb-ft).
    
    
    
    

12. Rotate assembly several times.
    
    
    
    

13. Check backlash as outlined in Step 7. If backlash is within specification, Go to Step 14. If not, repeat Step 10.

14. Increase both LH and RH shim sizes by 0.1524mm (0.006-inch) and install for correct differential bearing preload. Make sure the shims are fully seated and the assembly turns freely.
    
    
    
    

15. Use a white marking compound to obtain a tooth mesh contact pattern in the assembly. Pattern legibility can be improved by connecting the driveshaft and rotating both tires in the drive and coast direction.

Tooth Contact Guidelines

Pattern inspection allows the technician to detect gross errors in set-up prior to complete reassembly. Pattern contact should be within the primary area of the ring gear tooth surface avoiding "narrow" or "hard" contact with the outer perimeter of tooth (top to root, toe to heel). Inspect pattern on the drive (pull) side. Correct assembly of drive pattern will result in satisfactory coast performance. If gross pattern error is detected, with preferred backlash, 0.305 to 0.381mm (0.012 to 0.015 inch), recheck pinion shim selection.