Rear Differential

Complete removal and replacement of the rear differential assembly on a 1972 Ford F-100 with 302ci V8, including driveshaft removal, axle disconnect, and differential fluid service.

Warnings

Tools required

Parts

• Rear differential assembly (rebuild or replacement as needed) × 1 — Use OEM specification for 9-inch Ford rear end
• Differential cover gasket × 1 — Use OEM specification
• Driveshaft U-joint strap bolts × 4 — 3/8"-16 x 1" Grade 8
• Differential mounting hardware (as needed) × 1 — Use OEM specification

Fluids

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

Preparation

1. Park vehicle on level, solid surface and engage parking brake firmly.
2. Chock front wheels securely on both sides.
3. Loosen rear wheel lug nuts while vehicle is still on ground (do not remove).
4. Raise rear of vehicle using floor jack at rear axle housing or frame-mounted lift points.
5. Install jack stands under frame rails immediately behind cab, ensuring stands are on solid frame metal.
6. Raise front of vehicle and install jack stands under front frame rails to create level working position.
7. Remove rear wheels completely and set aside.
8. Spray all differential mounting bolts, U-joint strap bolts, and brake line brackets with penetrating oil and allow to soak for 15-20 minutes.

Procedure

1. 1

   Drain differential fluid
   Position drain pan under differential cover. Remove the differential cover bolts using a 1/2" socket, working in a crisscross pattern from top to bottom. Carefully pry cover loose with pry bar at designated pry points (bottom corners) and allow gear oil to drain completely. Remove cover and old gasket material. Inspect drained fluid for metal shavings or debris indicating internal wear. Verified detail (The Ford 9-inch is an integral-carrier (drop-out third member) design — the 'cover' is the removable center section (pumpkin) held by ~10 nuts on studs, not a stamped rear cover with bolts like a GM 10-bolt. Draining is done via a fill/drain plug or by removing the third member, not by prying off a rear cover. This step misrepresents the 9-inch architecture. If the truck actually has an 8-inch, same integral-carrier issue applies.): The Ford 9-inch (and 8-inch) uses an integral carrier (drop-out third member), not a rear stamped cover. Drain gear oil by removing the fill/drain plug on the housing, or drain when removing the center section. There is no bolt-on rear cover to pry off on these axles.
2. 2

   Mark and disconnect driveshaft
   Using marking paint, create alignment marks on the driveshaft yoke and pinion flange showing exact rotational position. These marks must align exactly on reassembly. Remove the 4 U-joint strap bolts at the rear pinion yoke using a 9/16" socket and wrench. Support driveshaft weight and separate the rear U-joint from the pinion flange, then carefully slide the front slip yoke out of the transmission tailshaft to remove the driveshaft. Secure driveshaft to frame with wire or mechanic's wire to prevent it from dropping.
3. 3

   Disconnect rear brake lines and emergency brake cables
   Locate the brake hose-to-hard line junction on the differential housing or axle tube. Using a flare nut wrench, disconnect brake line at the junction (typically 3/8" or 7/16" flare nut). Cap or plug the open line immediately to prevent fluid loss and contamination. Disconnect emergency brake cables from the cable guides and brackets on the differential housing, noting routing for reinstallation. Remove any brackets securing brake lines to the axle housing using appropriate sockets.
4. 4

   Disconnect rear shock absorbers
   Locate the lower shock absorber mounting bolts at the rear axle housing brackets. Remove both lower shock mounting bolts using a 9/16" socket and wrench combination. The shocks will remain attached at the upper frame mounts. Allow shocks to hang freely or tie them up to the frame to keep them out of the work area.
5. 5

   Support differential assembly
   Position a transmission jack or floor jack with a wide wood block (minimum 12" x 12") directly under the center of the differential housing. Raise jack until it just makes contact and supports the weight of the assembly without lifting. The leaf springs should still be carrying some load at this point. Ensure jack is stable and centered to prevent the differential from shifting during removal.
6. 6

   Remove U-bolts and spring plates
   Remove the 8 U-bolt nuts (4 U-bolts total, 2 per side) securing the axle housing to the leaf springs using a 3/4" socket. The U-bolts wrap around the axle tubes and through the spring perch. Once all nuts are removed, lift U-bolts up and out of the spring pack. Remove the spring plates from the top of each axle tube.
7. 7

   Lower and remove differential assembly
   With an assistant spotting, slowly lower the transmission jack while guiding the differential assembly down and away from the leaf springs. The assembly will need to move down approximately 4-6 inches before clearing the spring packs. Once clear of springs, carefully roll the differential assembly out from under the vehicle. Exercise extreme caution due to the weight of the assembly (150-200 lbs). Keep the assembly level during removal to prevent it from tipping off the jack.
8. 8

   Inspect and prepare mounting surfaces
   With differential removed, inspect leaf spring pads and U-bolt threads for damage or excessive wear. Wire brush all mating surfaces on the spring packs where the spring plates and axle housing contact. Inspect brake lines, shock mounts, and frame components for any damage. Clean all mounting hardware with wire brush and inspect U-bolts for thread damage or bending. Replace any damaged components before reinstalling differential.
9. 9

   Position replacement differential assembly
   If installing a replacement or rebuilt differential, ensure it is the correct housing for your application (check axle tube length and spring perch location). Position the differential assembly on the transmission jack and carefully roll it into position under the vehicle. With an assistant guiding, raise the jack slowly while aligning the axle tubes with the leaf spring packs. The spring perches on the axle tubes must seat properly on top of the leaf springs. This may require small adjustments in jack position.
10. 10

    Install U-bolts and spring plates
    Once the axle housing is properly seated on the leaf springs, position the spring plates over the top of each axle tube. Install the 4 U-bolts by threading them up through the leaf springs and through the holes in the spring plates. Thread U-bolt nuts onto all 8 U-bolt legs and tighten in a crisscross pattern (front-to-rear on each side) using a 3/4" socket. Torque U-bolt nuts to specification in multiple passes. Ensure spring plates remain centered and flat during tightening.
11. 11

    Reconnect shock absorbers
    Align the lower shock absorber eyes with the mounting brackets on the axle housing. Install lower shock mounting bolts and tighten using a 9/16" socket and wrench. Torque to specification. Ensure shock absorbers are not twisted or binding.
12. 12

    Reconnect driveshaft
    Carefully slide the front slip yoke back into the transmission tailshaft and mate the rear U-joint to the pinion flange, ensuring the alignment marks made during disassembly line up exactly. The yoke should slide on smoothly without forcing. Align the U-joint bearing caps with the pinion flange and install the 4 U-joint strap bolts with their retaining straps. Tighten bolts in a crisscross pattern using a 9/16" socket. 26.0 lb-ft (35.0 Nm). Verify alignment marks still match after tightening.
13. 13

    Reconnect brake lines and emergency brake cables
    Reconnect the brake hard line to the flexible hose at the junction on the axle housing using a flare nut wrench. Tighten securely but do not overtighten flare fittings. Reinstall any brake line brackets to the axle housing. Route emergency brake cables through their guides and brackets on the differential housing, matching the original routing pattern. Secure all cable brackets and guides.
14. 14

    Install differential cover and fill with gear oil
    Clean all old gasket material from the differential cover and housing mating surfaces using a scraper and wire brush. Install new differential cover gasket (use gasket sealer if specified). Position cover and install all cover bolts finger-tight. Tighten bolts in a crisscross pattern using a 1/2" socket. Torque to specification in multiple passes. Using a gear oil pump or squeeze bottle, add 80W-90 GL-5 gear oil through the fill plug hole (located on the carrier/center section) until oil reaches the bottom of the fill plug threads. If this axle is a limited-slip (Traction-Lok) unit, add the required friction modifier additive. Install and tighten fill plug. Total capacity is approximately 2.25-2.5 quarts for the 9-inch (verify against OEM spec); fill until oil reaches the bottom of the fill plug hole rather than by volume. Verified detail (Same integral-carrier issue: there is no bolt-on service cover with a cover gasket on the Ford 9-inch/8-inch. The gasket seals the third-member center section to the housing, retained by nuts on studs. Referencing a bolt-on cover is factually wrong for this platform.): If the center section (third member) was removed, clean the housing and carrier mating flange, install a new pumpkin gasket, and torque the carrier retaining nuts to specification in a crisscross pattern. These axles do not use a bolt-on rear service cover.
15. 15

    Bleed brake system
    Since brake lines were disconnected, the brake system must be bled. Check master cylinder reservoir and top off with fresh DOT 3 or DOT 4 brake fluid as specified for your vehicle. Beginning with the wheel furthest from the master cylinder (typically right rear), bleed each wheel cylinder using the bleeder screw until all air is removed and firm pedal feel is restored. Repeat for all four wheels. Check for brake fluid leaks at the reconnected junction.

Reassembly

1. Reinstall rear wheels and torque lug nuts to specification in a star pattern.
2. Lower vehicle from jack stands carefully, ensuring all tools and parts are clear.
3. Remove wheel chocks and perform final torque check on all lug nuts with vehicle on ground.
4. Test parking brake engagement and adjust cable tension if necessary.

Verification

• Start engine and pump brake pedal several times to verify firm pedal feel with no pedal fade.
• Inspect all brake line connections and differential cover for fluid leaks.
• Test drive vehicle at low speed (under 15 mph) in a safe area to verify proper differential operation and brake function.
• Listen for any unusual noises from the differential (whining, grinding, or clunking).
• After test drive, recheck differential fluid level at fill plug and top off if necessary.
• Inspect for gear oil leaks at pinion seal and differential cover after 50-100 miles of driving.
• After 500 miles, retorque all U-bolt nuts and verify all fasteners remain tight.

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