Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCHEVROLET1971P20 VAN 4.1L ENG VIN CREPAIR AND DIAGNOSIS (SINGLE PAGE)DRIVELINES & AXLESDIFFERENTIALS & DRIVE AXLESDRIVE AXLES - TOOTH CONTACT PATTERNSTOOTH CONTACT PATTERNSGEAR BACKLASH & PINION SHIM CHANGES
1971 Chevrolet P20 Van 4.1L Eng VIN C
Gear Backlash & Pinion Shim Changes
1971 Chevrolet P20 Van 4.1L Eng VIN CSECTION Gear Backlash & Pinion Shim Changes
NOTE:
Backlash is adjusted by shifting shims from one side of differential case to the other or by turning adjusting nuts. Changing pinion shims changes distance from top of pinion to centerline of ring gear.
- With no 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.
- With no 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.
- With no 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, a 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.
RENDER: 1.0x
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.