Ring and Pinion

Replace the ring and pinion gears in the rear differential of a 1966 Corvette, including differential disassembly, gear setup, and backlash/pattern adjustment.

Warnings

Tools required

Parts

• Ring and pinion gear set (specify ratio) × 1 — Use OEM specification or aftermarket equivalent
• Pinion bearing kit (front and rear bearings with races) × 1 — Use OEM specification
• Pinion seal × 1 — Use OEM specification
• Pinion shims (assortment) × 1 — Typically 0.003 to 0.012 inch
• Carrier bearing set (left and right) × 1 — Use OEM specification
• Carrier shims (assortment) × 1 — Typically 0.005 to 0.030 inch
• Ring gear bolts × 10 — Use OEM specification
• Pinion nut (crush sleeve style) × 1 — Use OEM specification
• Crush sleeve × 1 — Use OEM specification
• Differential cover gasket × 1 — Use OEM specification or RTV silicone
• Gear marking compound × 1 — Prussian blue
• RTV silicone sealant × 1 — High-temperature rated

Fluids

• 75W-90 GL-5 Gear Oil — 2 qt

Preparation

1. Park vehicle on level ground and chock front wheels
2. Raise rear of vehicle and support securely on jack stands under frame rails
3. Remove both rear wheels
4. Mark driveshaft and pinion yoke relationship for reinstallation alignment
5. Clean exterior of differential housing and cover thoroughly
6. Verify new ring and pinion set serial numbers match
7. Organize all measuring tools and shims on clean work surface

Procedure

1. 1

   Drain differential and remove cover
   Place drain pan under differential. Remove the 10 differential cover bolts and carefully pry cover off using a flat blade. Allow gear oil to drain completely. Remove and discard old gasket material from both cover and housing mating surfaces. Clean surfaces with solvent and wire brush.
2. 2

   Remove driveshaft and mark bearing caps
   Remove the 4 U-joint strap bolts at the pinion yoke. Slide driveshaft rearward to disengage from pinion and lower away. Use a center punch to mark the driver and passenger side carrier bearing caps and their corresponding housing positions (1 mark driver, 2 marks passenger). This ensures correct reinstallation orientation.
3. 3

   Measure and record original backlash and preload
   Mount dial indicator against ring gear tooth face. Rock ring gear back and forth while holding pinion stationary. Record backlash reading (should be 0.005 to 0.009 inch on original setup). Mark pinion nut position relative to yoke with paint pen. Using an inch-pound torque wrench on the pinion nut, measure and record rotational torque required to turn pinion (typically 15-25 inch-pounds with new bearings, less with used). These readings provide baseline reference.
4. 4

   Remove carrier assembly
   Remove the 4 carrier bearing cap bolts (2 per cap). Carefully pry carrier assembly out of housing using pry bars on both sides simultaneously to avoid cocking. If tight, use case spreader tool to expand housing slightly (no more than 0.015 inch spread). Remove carrier with ring gear attached. Remove and save carrier bearing shims, keeping driver and passenger side shims separate and labeled.
5. 5

   Remove pinion nut and yoke
   Hold pinion yoke stationary using holder tool or large channel locks on yoke ears. Remove pinion nut (typically 1 inch hex). Mark yoke orientation on pinion shaft. Use puller to remove yoke from pinion shaft. Remove and discard pinion seal.
6. 6

   Remove pinion assembly
   Carefully drive pinion shaft rearward out of housing using soft-face hammer. The rear bearing, crush sleeve, and front bearing will come out with pinion. Catch assembly to prevent damage. Remove crush sleeve from pinion shaft and discard. Remove front and rear pinion bearings from pinion shaft using bearing separator and press. Remove front and rear bearing races from housing using race puller or brass punch.
7. 7

   Remove old ring gear from carrier
   Secure carrier in soft-jawed vise. Remove the 10 ring gear bolts (left-hand thread on some applications, verify direction before applying force). Tap ring gear off carrier using soft-face hammer if tight. Clean carrier face and ring gear mounting surface thoroughly.
8. 8

   Install new ring gear on carrier
   Align new ring gear on carrier, ensuring bolt holes align. Install new ring gear bolts and tighten in crossing pattern in 3 stages to final specification. Clean bolt threads and apply thread locker per manufacturer specification. Verify ring gear is seated flush against carrier face with no gaps.
9. 9

   Determine pinion depth shim thickness
   Install front and rear pinion bearing races in housing using bearing race installer or press, seating fully. Check pinion depth code stamped on pinion gear head (example: +2, -3, or 0). This indicates deviation in thousandths from nominal depth. Use pinion depth gauge tool to measure required shim thickness behind rear pinion bearing. A zero-marked pinion typically requires 0.008 to 0.010 inch shim. Adjust shim thickness per pinion variance marking (add 0.002 inch for -2 marking, subtract 0.002 inch for +2 marking).
10. 10

    Install pinion bearings and depth shim
    Place calculated shim(s) behind rear pinion bearing on pinion shaft. Press rear pinion bearing onto pinion shaft until fully seated against shim. Press front pinion bearing onto pinion shaft. Install pinion assembly into housing from rear, carefully guiding through front bearing race. Install new crush sleeve on pinion shaft from front.
11. 11

    Install yoke and set pinion bearing preload
    Install pinion yoke on shaft, aligning marks made during disassembly. Install new pinion nut and tighten in stages while checking rotational torque. Tighten to approximately 200 ft-lbs initially, then check preload with inch-pound torque wrench. Target preload is 20-25 inch-pounds for new bearings. Continue tightening pinion nut in small increments and rechecking until correct preload is achieved. Once correct preload is reached, DO NOT back off nut or preload will be lost and crush sleeve must be replaced.
12. 12

    Install carrier assembly with initial shims
    Press carrier bearings onto carrier (if removed) using bearing installer. Start with original shim thickness removed earlier, or use 0.010 inch on each side as starting point for new setup. Install carrier assembly into housing, tapping bearing races into bores. Install bearing caps in correct orientation per punch marks. Install cap bolts and tighten in crossing pattern to secure carrier.
13. 13

    Measure and adjust backlash
    Mount dial indicator against ring gear tooth face perpendicular to tooth angle. Rock ring gear back and forth while holding pinion stationary. Measure backlash. Target specification is 0.006 to 0.008 inch. If backlash is too tight (less than 0.006 inch), move shim thickness from passenger side to driver side. If backlash is too loose (greater than 0.008 inch), move shim thickness from driver side to passenger side. Moving 0.005 inch shim changes backlash approximately 0.003 inch. Remove carrier, adjust shims, reinstall, and recheck. Repeat until backlash is within specification.
14. 14

    Check and adjust gear tooth contact pattern
    Apply thin coat of gear marking compound to 8-10 ring gear teeth in 3 locations around ring. Rotate pinion forward and backward through marked teeth with moderate resistance applied to ring gear. Examine contact pattern on both drive (forward rotation) and coast (reverse rotation) sides. Proper pattern should be centered on tooth face, slightly toward toe (inner edge). If pattern is too deep toward root (pinion too deep), add shim behind pinion rear bearing. If pattern is too shallow toward top land (pinion too shallow), remove shim. Each 0.003 inch shim change moves pattern noticeably. If pattern is toward heel (outer edge), move carrier shims toward ring gear side. If toward toe (inner edge), move shims away from ring gear side. Adjust pinion depth or carrier position as needed, recheck backlash after each change, and repeat pattern check until optimal.
15. 15

    Verify final specifications and seal differential
    Perform final backlash check at 4 positions around ring gear (every 90 degrees). Backlash should be 0.006 to 0.008 inch at all positions with no more than 0.002 inch variation. Verify pinion bearing preload remains at 20-25 inch-pounds. Clean differential cover and housing mating surfaces. Apply 1/8 inch bead of RTV silicone sealant to cover or install new gasket. Install cover and tighten bolts in crossing pattern. Allow RTV to cure per manufacturer instructions before filling.
16. 16

    Reinstall driveshaft and fill differential
    Align driveshaft yoke with pinion yoke per marks made during disassembly. Install U-joint straps and tighten bolts securely. Remove differential fill plug. Fill differential with 75W-90 GL-5 gear oil until oil reaches bottom of fill hole (approximately 2.0 quarts). Allow to stabilize and top off if needed. Install fill plug and tighten securely.

Reassembly

1. Install rear wheels and tighten lug nuts to specification in star pattern
2. Lower vehicle to ground
3. Test drive vehicle at varying speeds and loads, listening for gear noise or vibration
4. After initial 50-100 miles, recheck differential for leaks and fluid level
5. After 500 miles, drain and refill gear oil to remove any break-in debris

Verification

• No gear whine or howling noise during acceleration or deceleration
• No clunking or binding when turning corners
• Differential cover shows no signs of leakage
• Pinion nut remains tight with no rotational movement
• Backlash remains within 0.006 to 0.008 inch specification after test drive
• Operating temperature is normal with no excessive heat from differential housing

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