Differential Bearing Preload & Ring Gear Backlash

1. With pinion depth set and pinion installed, place differential case and gear assembly with bearings and cups into axle housing. Install a .265" (6.7 mm) shim on left side (ring gear side) of differential.
2. Install left bearing cap, and finger tighten bolts. Select largest shim that will fit with a slight drag, and install it onto right side (pinion gear side) of differential. Install right bearing cap. Tighten all cap bolts to specification. See TORQUE SPECIFICATIONS  .
3. Rotate ring gear to ensure free operation. Check ring gear backlash. See Fig 1 . Ring gear backlash should be within specification. See AXLE ASSEMBLY SPECIFICATIONS  . If ring gear backlash is zero, go to step  4 . If ring gear backlash is not within specification, go to step  5 . If ring gear backlash is within specification, go to step  7 .
   Fig 1: Measuring Ring Gear Backlash

   Courtesy of FORD MOTOR CO.
4. Add .020" (.51 mm) to shim size on right side, and subtract .020" (.51 mm) from shim size on left side. Check ring gear backlash. If ring gear backlash is within specification, go to step  7 . If ring gear backlash is not within specification, go to next step.
5. Increase shim thickness on one side, and decrease shim thickness on opposite side by same amount. See Fig 2 . See BACKLASH-TO-SHIM THICKNESS CONVERSION  table for approximate shim change.
   BACKLASH-TO-SHIM THICKNESS CONVERSION
   
   

   Required Change In Backlash - In. (mm)	Required Change In Shim Thickness - In. (mm)
   .001 (.03)	.002 (.05)
   .002 (.05)	.002 (.05)
   .003 (.08)	.004 (.10)
   .004 (.10)	.006 (.15)
   .005 (.13)	.006 (.15)
   .006 (.15)	.008 (.20)
   .007 (.18)	.010 (.25)
   .008 (.20)	.010 (.25)
   .009 (.23)	.012 (.30)
   .010 (.25)	.014 (.36)
   .011 (.28)	.014 (.36)
   .012 (.30)	.016 (.41)
   .013 (.33)	.018 (.46)
   .014 (.36)	.018 (.46)
   .015 (.38)	.020 (.51)

6. Install shim and bearing caps. Tighten bearing cap bolts to specification. See TORQUE SPECIFICATIONS  . Rotate ring gear several times. Recheck ring gear backlash. If ring gear backlash is within specification, go to next step. If ring gear backlash is not within specification, repeat step  5 .
7. Increase both left and right shim sizes by .006" (.15 mm), and reinstall for correct bearing preload. Ensure shims are fully seated and ring gear assembly turns freely. Using marking compound, check gear tooth contact pattern. See GEAR TOOTH CONTACT PATTERNS article in GENERAL INFORMATION.

Fig 2: Adjusting Ring Gear Backlash

Courtesy of FORD MOTOR CO.