GEAR TOOTH CONTACT PATTERNS
1988 Jeep Cherokee
Gear Tooth Contact Patterns
* PLEASE READ THIS FIRST *
The following article is for GENERAL INFORMATION purposes only. Information does not SPECIFICALLY apply to all years, makes and models, but is to be used as a general reference guide.
Wipe lubricant from internal parts. Rotate gears and inspect for wear or damage. Mount dial indicator to housing, and check backlash at several points around ring gear. Backlash must be within specifications at all points. If no defects are found, check gear tooth contact pattern.
GEAR TOOTH CONTACT PATTERN
NOTE: Drive pattern should be well centered on ring gear teeth.
Coast pattern should be centered, but may be slightly toward toe of ring gear teeth.
gear teeth with marking compound. Wrap cloth or
rope around drive pinion flange to act as brake. Rotate ring gear
until clear tooth contact pattern is obtained.
pattern will indicate whether correct pinion
bearing mounting shim has been installed and if drive gear backlash
has been set properly. Backlash between drive gear and pinion must be
maintained within specified limits, until correct tooth pattern is
BACKLASH CORRECT Thicker Shim Required
Fig. 1: Drive Axle Gear Tooth Patterns
GEAR BACKLASH & PINION SHIM CHANGES
NOTE: Backlash is adjusted by either moving shims from one side of differential case to the other or by turning adjusting nuts on which side bearing races ride. Changing of pinion shims alters the distance from face of pinion of centerline of ring gear.
change in backlash, moving pinion further from
ring gear moves drive pattern toward heel and top of tooth, and moves
coast pattern toward toe and top of tooth.
change in backlash, moving pinion closer to ring
gear moves drive pattern toward toe and bottom of tooth, and moves
coast pattern toward heel and bottom of tooth.
change in pinion shim thickness, an increase in
backlash moves ring gear further from pinion. Drive pattern moves
toward heel and top of tooth, and coast pattern moves toward heel and
top of tooth.
With no change in pinion shim thickness, decrease in
backlash moves ring gear closer to pinion gear. Drive pattern moves toward toe and bottom of tooth, and coast pattern moves toward toe and bottom of tooth.