After setting the pinion depth, backlash, and the pinion bearing preload, set the carrier bearing preload. Three different shim or adjustment methods, screw adjusters, outside shim design, and inside shim design, cover most differentials.
Screw Adjuster Design
The easiest method uses screw adjusters to set the backlash and carrier bearing preload. Carefully oil the adjuster threads on both the housing and on the adjusters themselves. Note the order in which you tighten the adjusters so the backlash remains consistent, even when subjected to heavy loads.
The pinion gear always forces the ring gear away from itself whenever it transfers power. Start with a looser backlash setting than the axle’s manufacturer calls for and always ensure that the last adjustment made to the left adjuster tightens it.
If the backlash becomes too tight, loosen the left adjuster first, followed by tightening the right adjuster. To reestablish the backlash setting, tighten the left adjuster. Ensure that the last adjustment made to the left adjuster tightens it to eliminate any space between it and its bearing race. Any space or looseness on the left side will let the carrier deflect when under load, and this will allow backlash to open up when driven under load.
Once the backlash approaches the manufacturer’s recommendations, tighten both left and right adjusters evenly to increase carrier bearing preload. Set the carrier bearing preload to approximately 150 to 200 pounds/feet. It is difficult to damage bearings with excessive carrier bearing preload on a screw-adjusted differential.
> If the preload is close and the backlash is too loose, tighten the left adjuster a notch or two until the backlash is correct and the preload is sufficient.
> If the preload is close and the backlash is too tight, tighten the right adjuster until the
backlash is correct and the preload is sufficient.
As stated before, ensure that the last adjustment made to the left adjuster tightens it. That will eliminate the possibility of a space between the adjuster and the bearing race.
Outside Shim Design
This design uses shims between the carrier bearing races and the housing. Initially set the backlash with very little carrier bearing preload. After setting the backlash, add equal amounts of shims to both sides of the carrier to set the carrier bearing preload as tight as possible without damaging the shims (carrier bearings in this axle design hardly ever fail due to excessive carrier bearing preload).
> If the preload is close and the backlash is loose, add shims to the left side. This increases the carrier bearing preload and tightens the backlash at the same time.
> If the preload is close and the backlash is too tight, add shims to the right side. This
increases both the carrier bearing preload and the backlash at the same time.
Inside Shim Design
This design uses shims between the carrier bearing and the case. Initially set the backlash tight and the preload light, as it will make carrier removal and installation easier. After setting the backlash, add equal amounts of shims to both sides until the correct preload is achieved.
> If the preload is close and the backlash is loose, add shims to the left side. This increases the carrier bearing preload and tightens the backlash at the same time.
> If the preload is close and the backlash is too tight, add shims to the right side. This
increases the carrier bearing preload and the backlash at the same time.