Ring and Pinion

This procedure covers the removal, inspection, and replacement of the ring and pinion gears in the rear differential of a 1970 AMC Rebel Machine with 390ci V8.

Warnings

Tools required

Parts

• Ring and pinion gear set (AMC 20 or Dana 44, verify axle type) × 1 — Match gear ratio to original specification
• Pinion bearing kit (inner and outer bearings with races) × 1 — Use OEM specification
• Carrier bearing set (side bearings) × 1 — Use OEM specification
• Pinion seal × 1 — Use OEM specification
• Pinion shims assortment × 1 — Use OEM specification
• Ring gear bolts × 1 — Use OEM specification or high-strength replacements
• Differential cover gasket or RTV silicone × 1 — Use OEM specification
• Crush sleeve or solid spacer (depending on design) × 1 — Use OEM specification
• Pinion nut × 1 — Use OEM specification
• Carrier bearing adjuster nuts or shims (if applicable) × 1 — Verify differential type

Fluids

• Hypoid gear oil (GL-5, 85W-140 or manufacturer specification) — 3 qt

Preparation

1. Park vehicle on level surface and apply parking brake
2. Chock front wheels securely
3. Raise rear of vehicle and support on jack stands at frame rails
4. Remove both rear wheels
5. Identify rear axle type (AMC 20 or Dana 44) by inspection or casting numbers
6. Ensure work area is clean and organized for precision measurement work

Procedure

1. 1

   Drain differential and mark components
   Place drain pan under differential cover. Remove all cover bolts and carefully pry cover loose to drain gear oil. Clean cover and housing mating surfaces. Mark driveshaft and pinion flange with paint or punch marks for proper reassembly alignment. Measure and record the amount of driveshaft end play for reference.
2. 2

   Remove driveshaft
   Remove the four U-bolts or straps securing the driveshaft to the pinion flange. Support driveshaft and slide it rearward out of the transmission tailshaft. Plug transmission output to prevent fluid leakage. Store driveshaft safely to avoid damage.
3. 3

   Remove axle shafts and carrier assembly access
   For AMC 20: Remove axle shaft retaining nuts from backing plate studs and pull axle shafts outward to clear carrier. For Dana 44: Remove differential cover bolts, then remove C-clips from axle shaft ends inside carrier and slide axle shafts outward. This provides access to the carrier assembly.
4. 4

   Remove pinion flange and measure preload
   Using an inch-pound torque wrench, measure and record the rotating torque required to turn the pinion (pinion bearing preload). This should be 15-25 in-lbs for new bearings. Mark the pinion nut position relative to pinion threads. Hold pinion flange with holding tool and remove pinion nut. Use a suitable puller to remove pinion flange from pinion shaft.
5. 5

   Remove pinion and bearings
   Carefully drive the pinion shaft rearward out of the housing using a soft-face hammer or press. Catch the pinion and note the orientation and position of all shims, crush sleeve or solid spacer, and bearings. Remove pinion seal from housing. Remove inner and outer pinion bearings and races from housing and pinion using bearing puller and press. Keep all shims organized and labeled for reference during setup.
6. 6

   Remove carrier bearing caps and differential assembly
   Mark carrier bearing caps for proper orientation (left/right, front/back). Remove carrier bearing cap bolts. If equipped with adjuster nuts, carefully note their position and thread engagement. Use pry bars to carefully lift the differential carrier assembly from the housing. Remove carrier bearings using bearing puller if replacement is required.
7. 7

   Remove old ring gear
   Secure differential carrier in soft-jaw vise or ring gear holding fixture. Remove ring gear bolts (typically left-hand thread). If bolts are tight, apply penetrating oil and use impact driver or heat carefully. Once bolts are removed, tap ring gear off carrier using soft hammer. Clean all surfaces thoroughly.
8. 8

   Clean and inspect all components
   Thoroughly clean differential housing, carrier, and all mounting surfaces with solvent. Inspect housing for cracks, stripped threads, or damage. Inspect carrier for wear, cracks, or damaged bearing surfaces. Check side gear and pinion gear condition. Replace carrier assembly if excessive wear is present. Clean and dry all bearing bores in housing.
9. 9

   Install new ring gear on carrier
   Heat new ring gear in oven to 250°F for 15-20 minutes to expand metal (do not exceed 300°F). Align ring gear bolt holes with carrier and tap ring gear onto carrier using soft hammer, ensuring it seats fully against carrier shoulder. Install new ring gear bolts with thread locker and tighten in crossing pattern. Allow assembly to cool completely before proceeding.
10. 10

    Install pinion depth and bearing races
    Press new pinion bearing races into housing using race driver. Ensure races are fully seated. Using pinion depth setting tool and manufacturer specifications (or shim from old pinion), determine correct pinion depth shim thickness. Install pinion depth shim behind inner pinion bearing race. This is critical for proper gear tooth contact pattern.
11. 11

    Assemble and install pinion
    Press inner pinion bearing onto pinion shaft. Install pinion into housing from rear with depth shim in place. Install crush sleeve or solid spacer over pinion shaft. Install outer pinion bearing, then install new pinion seal using seal driver. Install pinion flange and new pinion nut. Gradually tighten pinion nut while checking rotating torque frequently with inch-pound torque wrench. Target preload is 20-25 in-lbs for new bearings (10-15 in-lbs for used bearings). Do not exceed specified preload as crush sleeve cannot be reused.
12. 12

    Install carrier bearings and set backlash
    Press new carrier bearings onto differential carrier if removed. Install carrier assembly into housing. Install carrier bearing caps in correct orientation. If using shim-type setup, install shims to achieve 0.005-0.009 inch backlash between ring and pinion gears. If using adjuster nut type, tighten adjusters to remove side play and achieve proper backlash. Measure backlash with dial indicator at multiple points around ring gear.
13. 13

    Check gear tooth contact pattern
    Apply gear marking compound to several ring gear teeth. Rotate pinion through several revolutions in both directions with light resistance. Examine contact pattern on gear teeth. Pattern should be centered on tooth face. Adjust pinion depth shims or carrier bearing shims/adjusters as needed to achieve proper contact pattern. This may require disassembly and reassembly multiple times to achieve correct pattern.
14. 14

    Final assembly and installation
    Once proper backlash and tooth contact are achieved, torque all carrier bearing cap bolts per specification. Install axle shafts (and C-clips if Dana 44). Clean differential cover and housing mating surfaces. Apply new gasket or RTV silicone bead. Install cover and torque bolts in crossing pattern. Install driveshaft aligning marks made during disassembly. Install rear wheels and torque lug nuts.
15. 15

    Fill with gear oil and test
    Fill differential with manufacturer-specified hypoid gear oil (typically GL-5 85W-140) to proper level (typically bottom of fill hole). Install fill plug. Lower vehicle to ground. Test drive vehicle and listen for abnormal gear whine or noise. Recheck differential oil level after test drive and top off if needed. Monitor for leaks over the next several days.

Reassembly

1. Ensure all bearings are properly seated and preloaded to specification
2. Verify ring gear backlash is within 0.005-0.009 inch specification at multiple points
3. Confirm gear tooth contact pattern is centered on tooth face before final assembly
4. Use new crush sleeve, pinion seal, and ring gear bolts for proper installation
5. Mark and align driveshaft to pinion flange in original orientation

Verification

• Check for gear oil leaks around pinion seal and differential cover after initial test drive
• Listen for abnormal gear whine, howling, or clunking during acceleration and deceleration
• Verify smooth operation through all driving conditions without vibration
• Recheck differential oil level after 100 miles and inspect for leaks
• Contact pattern should be verified as centered on ring gear teeth with minimal noise during operation

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