Jeep Cherokee

 Service Manual

Differential and driveline » Tube, 181, and 186 FBI axle » Adjustments
Gear contact pattern analysis

The ring gear and pinion teeth contact patterns will show if the pinion depth is correct in the axle housing. It will also show if the ring gear backlash has been adjusted correctly. The backlash can be adjusted within specifications to achieve desired tooth contact patterns.

(1) Apply a thin coat of hydrated ferric oxide, or equivalent, to the drive and coast side of the ring gear teeth.

(2) Wrap, twist, and hold a shop towel around the pinion yoke to increase the turning resistance of the pinion. This will provide a more distinct contact pattern.

Fig. 103 Ring Gear Backlash Measurement

1 - DIAL INDICATOR

Fig. 104 Backlash Shim Adjustment

(3) Using a boxed end wrench on a ring gear bolt, Rotate the differential case one complete revolution in both directions while a load is being applied from shop towel.

The areas on the ring gear teeth with the greatest degree of contact against the pinion teeth will squeegee the compound to the areas with the least amount of contact. Note and compare patterns on the ring gear teeth to Gear Tooth Contact Patterns chart (Fig.

105) and adjust pinion depth and gear backlash as necessary.

Fig. 105 Gear Tooth Contact Patterns

181 FBI pinion gear depth

186 FBI pinion gear depth

181 FBI differential bearing preload and gear backlash

186 FBI differential bearing preload and gear backlash

Gear contact pattern analysis