Ring and Pinion

This procedure covers the complete removal, replacement, and setup of the ring and pinion gears in the rear differential of a 1972 Ford F-100 with 302ci V8.

Warnings

Tools required

Parts

• Ring and pinion gear set (specify ratio) × 1 — Use OEM specification or aftermarket equivalent
• Pinion bearing kit (inner and outer bearings with races) × 1 — Use OEM specification
• Carrier bearing kit (both sides with races) × 1 — Use OEM specification
• Pinion seal × 1 — Use OEM specification
• Pinion crush sleeve × 1 — Use OEM specification
• Pinion nut × 1 — Use OEM specification
• Ring gear bolts × 10 — Use OEM specification or Grade 8
• Differential cover gasket or RTV silicone × 1 — Use OEM specification or Permatex Ultra Grey
• Carrier shims (assorted thickness) × 1 — Typically 0.003"-0.030" range
• Pinion shims (assorted thickness) × 1 — Typically 0.003"-0.030" range

Fluids

• 80W-90 GL-5 rear differential fluid — 3.5 qt

Preparation

1. Park vehicle on level concrete surface and engage parking brake firmly.
2. Chock front wheels securely on both sides.
3. Raise rear of vehicle and support on jack stands placed under frame rails, ensuring rear axle can be lowered slightly if needed.
4. Remove both rear wheels to allow axle to settle and provide clearance.
5. Place drain pan under differential.
6. Clean exterior of differential housing thoroughly to prevent contamination during disassembly.
7. Mark driveshaft and pinion yoke with paint or punch marks for installation reference.

Procedure

1. 1

   Drain differential and remove cover
   Determine axle type. If a Ford 9-inch drop-out axle is fitted, there is no rear cover — remove the driveshaft and unbolt the third-member center section to service on a bench (verify nut/bolt count). If an integral-carrier axle with a rear cover is fitted, remove the cover bolts (verify count against the specific axle), carefully pry cover away using a gasket scraper or pry bar, allow all gear oil to drain into a drain pan, remove and discard old gasket material, and clean both mating surfaces thoroughly with gasket scraper and solvent. Verified detail (Ford 9-inch differentials typically use 12 cover bolts, not 10. The 10-bolt count appears to be incorrect for this housing design.): Remove the differential cover bolts (typically 12 on Ford 9-inch housings) and carefully pry cover away from housing using a gasket scraper or pry bar.
2. 2

   Remove driveshaft
   Remove the U-joint strap or U-bolt fasteners at the rear axle pinion yoke (verify exact count and type for your driveshaft). Support driveshaft and slide it rearward to separate from pinion yoke. Lower driveshaft and remove from vehicle. Stuff a clean rag into the transmission tailshaft housing to prevent fluid loss and contamination.
3. 3

   Remove pinion flange and seal
   Hold pinion flange stationary and remove pinion nut using appropriate socket. Mark rotational position of flange on pinion shaft if not previously marked. Use a suitable puller to remove pinion flange from shaft. Carefully pry out pinion seal using seal puller or screwdriver, taking care not to damage housing bore.
4. 4

   Measure and record original pinion depth
   Before removing pinion, install dial indicator on housing with stylus contacting pinion gear face. Zero the indicator and note any markings on pinion head (typically +1, 0, -1, etc.) which indicate variance from nominal depth in thousandths of an inch. Record these measurements for reference during reassembly.
5. 5

   Remove pinion gear assembly
   Tap pinion shaft rearward through the housing using soft-face hammer. The pinion will slide out the back with inner bearing cone, crush sleeve, and shims. Catch these components and keep them organized. Remove outer pinion bearing race and inner pinion bearing race from housing using bearing race puller and slide hammer.
6. 6

   Install case spreader and mark carrier position
   If an integral-carrier axle is fitted, install the case spreader tool per manufacturer instructions. NOTE: Ford 9-inch carriers typically use threaded adjuster nuts (not spreader/shims) to set carrier preload and backlash and are serviced as a removed third member on a bench — do not use a case spreader on a 9-inch. Before spreading case, use a dial indicator to measure and record existing carrier bearing preload and side-to-side position. Note orientation of any existing shims behind carrier bearings on both sides. Carefully spread case approximately 0.015" maximum to relieve tension on carrier bearings.
7. 7

   Remove carrier assembly
   With case spread, remove the carrier bearing caps (marked R and L for right and left). Note the position and thickness of any shims. Carefully pry carrier assembly upward and remove from housing. Keep bearing caps with their respective sides and keep all shims organized by location.
8. 8

   Remove ring gear from carrier
   Support carrier in vise using soft jaws or wood blocks to avoid damage. Remove the ring gear bolts (verify count for your carrier). IMPORTANT: Many Ford 9-inch ring gear bolts are LEFT-HAND thread — confirm thread direction before loosening, as left-hand bolts are removed by turning clockwise. Tap ring gear off carrier using soft-face hammer, working evenly around the gear. Clean carrier mounting surface thoroughly.
9. 9

   Remove and press new carrier bearings
   Use bearing separator and hydraulic press to remove old carrier bearings from carrier. Press new carrier bearings onto carrier using bearing driver and press, ensuring bearings seat fully against carrier shoulders. Do not press on bearing cages, only on inner races.
10. 10

    Install new ring gear on carrier
    Align new ring gear on carrier, ensuring bolt holes align properly and gear face direction matches original orientation. Install new ring gear bolts with medium-strength threadlocker. Tighten bolts in a star pattern in three stages: first to 20 ft-lb, then to 40 ft-lb, and finally to 50-55 ft-lb. Verify all bolts are torqued evenly. Verified detail (Ford 9-inch ring gear bolts are frequently left-hand thread; installing standard replacement bolts without confirming thread direction risks cross-threading/failure. Also the 70 ft-lb final spec is flagged as unverified — factory Ford 9-inch ring gear bolt torque is commonly around 70-80 ft-lb but must be confirmed for the specific carrier.): Install new ring gear bolts (confirm correct thread direction — many Ford 9-inch ring gear bolts are LEFT-HAND thread) with medium-strength threadlocker. Tighten evenly in a star pattern in stages up to the factory specification (verify: typically approximately 70-80 ft-lb for a Ford 9-inch).
11. 11

    Determine pinion depth shim thickness
    Using pinion depth setting gauge tool, measure required shim pack thickness to achieve proper pinion depth. Compare new pinion variance marking (on gear head) with old pinion marking. Each 0.001" change in marking requires corresponding shim adjustment. Install calculated shim pack on pinion shaft behind inner bearing race location.
12. 12

    Press pinion bearings and races
    Press new outer pinion bearing race into housing front bore using bearing race driver and press or hammer. Press new inner bearing race into housing rear bore. Ensure races are fully seated. Press inner pinion bearing onto pinion shaft using bearing driver and press, seating firmly against shim pack.
13. 13

    Install pinion assembly with crush sleeve
    Lubricate inner bearing with gear oil. Install pinion through housing from rear with shims and inner bearing in place. Install new crush sleeve over pinion shaft. Lubricate outer bearing with gear oil and install on pinion shaft. Install pinion flange, aligning marks made during disassembly.
14. 14

    Set pinion bearing preload
    Install new pinion nut and tighten gradually while rotating pinion to seat bearings. Check rotating torque frequently using inch-pound torque wrench on pinion nut. Target preload is 15-25 inch-pounds for new bearings with seal installed. Once proper preload is achieved, do NOT loosen nut as crush sleeve cannot be reused. If preload is exceeded, entire crush sleeve must be replaced and process repeated.
15. 15

    Install new pinion seal
    Lubricate new pinion seal lip with gear oil. Using seal driver of appropriate size, carefully drive seal into housing bore until flush with housing face. Ensure seal is not cocked and seats evenly.
16. 16

    Install carrier assembly with shims
    Remove case spreader. Place carrier assembly into housing with initial shim pack (start with shims 0.010" thinner than original on each side). Spread case 0.015" and seat carrier into position. Install bearing caps in correct orientation (marked L and R) and install cap bolts finger-tight.
17. 17

    Set carrier bearing preload and backlash
    Adjust shim thickness on both sides of carrier to achieve 0.006"-0.010" backlash between ring and pinion (measured at ring gear with dial indicator). To increase backlash, move shim thickness from ring gear side to opposite side (keeping total thickness constant). To decrease backlash, move shim thickness toward ring gear side. Once backlash is correct, add 0.004"-0.006" total shim thickness (split between both sides) to set carrier bearing preload. Torque bearing cap bolts to 50-60 ft-lb. Verified detail (Carrier bearing cap bolt torque of 70 ft-lb is unverified for this platform (flagged in openQuestions). Additionally, a Ford 9-inch uses threaded adjuster nuts rather than shims for carrier preload/backlash, so the shim method may not apply.): Once backlash is correct, set carrier bearing preload using the appropriate method for your carrier (threaded adjuster nuts on a Ford 9-inch, or shim packs on an integral-carrier design). Torque bearing cap bolts to the factory specification (verify for your axle).
18. 18

    Check gear pattern with marking compound
    Apply thin coat of gear marking compound to 4-6 teeth on ring gear. Rotate pinion through several revolutions in both directions while applying light resistance to ring gear. Examine contact pattern on ring gear teeth. Pattern should be centered on tooth face, slightly toward toe and centered vertically. Adjust pinion depth (shims behind inner bearing) or backlash (carrier shims) as needed until proper pattern is achieved. This may require disassembly and reassembly with corrected shims.
19. 19

    Verify final measurements
    With final shim selection installed, verify pinion rotating torque is still 15-25 inch-pounds. Verify ring gear backlash at four points around gear (90° intervals) is within 0.006"-0.010" and does not vary more than 0.002" between measurements. Verify carrier has slight drag when rotated by hand indicating proper bearing preload.
20. 20

    Install differential cover
    Clean cover and housing mating surfaces with solvent. Apply 1/4" bead of RTV silicone to cover (or install new gasket per manufacturer preference). Install cover and torque the cover bolts (typically 12) in criss-cross pattern to 15-20 ft-lb. Allow RTV to cure per manufacturer instructions (typically 1 hour) before filling with fluid.
21. 21

    Reinstall driveshaft
    Remove rag from transmission tailshaft. Slide driveshaft into transmission and align U-joint with pinion yoke, matching marks made during disassembly. Install the U-joint strap or U-bolt fasteners (same count as removed) and torque to the factory specification in a criss-cross pattern (verify torque for your driveshaft). Verified detail (Factory torque specification for driveshaft U-joint strap bolts on 1972 F-100): 26.0 lb-ft (35.0 Nm)
22. 22

    Fill differential with gear oil
    Remove differential fill plug from housing side. Using fluid pump or squeeze bottle, add 80W-90 GL-5 gear oil until fluid level reaches bottom of fill hole (a Ford 9-inch typically holds approximately 4-5 pints / 2-2.5 quarts — fill to the bottom of the fill hole rather than by quantity). Install fill plug and torque to the factory specification (verify). Wipe exterior clean. Verified detail (Differential fill plugs are typically NPT pipe threads that torque to 10-15 ft-lb; 25 ft-lb is excessive and risks cracking the housing.): Install fill plug and torque to 10-15 ft-lb.

Reassembly

1. Reinstall rear wheels and torque lug nuts to 140 ft-lb in star pattern.
2. Lower vehicle to ground and remove jack stands.
3. Test drive vehicle at low speeds initially, listening for any unusual noise from differential.
4. Check for leaks around differential cover and pinion seal after first test drive.
5. Re-check differential fluid level after 50 miles of driving and top off if needed.

Verification

• With vehicle on ground, shift transmission through all gears and verify smooth operation with no binding or unusual noise from differential.
• Drive vehicle at speeds up to 45 mph and verify no whining, howling, or grinding noise from differential under acceleration, deceleration, and steady cruise.
• Check for gear oil leaks around differential cover, pinion seal, and axle tube seals after 50-100 miles of operation.
• Verify no excessive heat buildup in differential housing during normal operation (touchable with bare hand after 20 minutes of driving).
• Listen for proper gear mesh sound: a slight whir is normal, but any howling, clicking, or grinding indicates improper setup requiring disassembly and correction.

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