Complete removal and replacement of the rear differential assembly on a 1966 Chevrolet Corvette, including draining gear oil, disconnecting driveshaft and axles, removing the differential unit, and reinstalling with new fluid.

Warnings

Tools required

Parts

• Rear differential gasket or RTV silicone × 1 — Use OEM specification
• Differential cover bolts (if corroded) × 1 — Use OEM specification
• U-joint strap bolts × 4 — 5/16"-18 x 3/4" Grade 8
• Differential mounting bolts (if damaged) × 1 — Use OEM specification

Fluids

• 75W-90 GL-5 Gear Oil — 2 qt

Preparation

1. Park vehicle on level, solid surface and place wheel chocks in front of front tires.
2. Release parking brake to allow free rotation of rear axles.
3. Raise rear of vehicle with floor jack and support securely on jack stands under frame rails.
4. Raise front of vehicle and support on jack stands to provide clearance for driveshaft removal.
5. Remove both rear wheels to access axle mounting hardware.
6. Place drain pan under differential cover.
7. Gather all tools and parts before beginning disassembly.

Procedure

1. 1

   Drain differential gear oil
   Remove all differential cover bolts using a 1/2" socket. There are 10 bolts securing the rear cover. Carefully pry cover away from housing with a flat-blade screwdriver or pry bar, allowing gear oil to drain into pan. Remove cover completely and set aside. Inspect old gasket material and clean mounting surface with wire brush if necessary.
2. 2

   Mark driveshaft orientation
   Using a punch or paint marker, make alignment marks on the driveshaft yoke and differential pinion yoke to ensure proper reassembly phasing. Mark both sides of the joint so orientation is unmistakable during reinstallation.
3. 3

   Disconnect rear driveshaft U-joint
   Remove the 4 U-joint strap bolts connecting the rear driveshaft to the differential pinion yoke using a 9/16" wrench and socket. Support the driveshaft while removing the final bolts to prevent it from dropping. Remove the U-joint straps and carefully slide the driveshaft rearward off the pinion shaft. Support or tie the driveshaft up out of the way to prevent damage to the front U-joint.
4. 4

   Disconnect rear axle shafts
   Remove the 4 bolts securing each axle flange to the differential side yoke using a 9/16" socket. There are 4 bolts per side (8 total). Carefully pull each axle shaft outward approximately 1-2 inches to disengage from the differential side gears, but do not remove completely from the trailing arm housing. Support axles so they do not hang on brake hoses.
5. 5

   Disconnect parking brake cable
   Locate the parking brake cable connection at the differential mounted parking brake caliper mechanism. Remove the cable retaining clip and disconnect the cable end from the brake lever. This is typically accessed from the right side of the differential housing.
6. 6

   Support differential housing
   Position a transmission jack or second floor jack under the center of the differential housing. Raise jack until it just contacts the housing and provides support. The differential should be stable but not lifting the vehicle. Ensure jack is centered to prevent the housing from tipping during removal.
7. 7

   Remove front differential mounting bolts
   Locate and remove the 2 bolts securing the front differential mounting bracket to the differential nose. These are typically 9/16" or 5/8" bolts accessible from above. Remove the bolts completely and retain the mounting bracket.
8. 8

   Remove rear differential mounting bolts
   Remove the 2 bolts securing the rear differential mounting bracket to the differential housing. These bolts pass through the differential carrier and mount to the frame. Use a 9/16" or 5/8" socket and be prepared to support the differential weight as you remove the final bolt.
9. 9

   Lower and remove differential assembly
   Carefully lower the transmission jack while guiding the differential assembly downward and forward. The pinion shaft will need to clear the driveshaft tunnel as you maneuver the unit. Once clear of the frame and suspension components, roll the jack and differential out from under the vehicle. Exercise caution as the assembly weighs 80-100 pounds.
10. 10

    Inspect and prepare replacement differential
    If installing a replacement differential, verify correct gear ratio and ensure all mounting brackets are transferred. Clean all mating surfaces on the replacement unit. If reusing the original differential, inspect all mounting points, pinion seal, and axle seals for damage or leaks. Replace seals as necessary before reinstallation.
11. 11

    Install differential assembly
    Position the differential on the transmission jack and roll it under the vehicle. Raise the jack while guiding the pinion shaft through the frame opening and aligning the differential with the mounting points. Ensure axle shaft splines are aligned with differential side gears. Raise until mounting holes align with frame brackets.
12. 12

    Install mounting bolts
    Install the rear mounting bolts first, threading them by hand to ensure proper alignment. Then install the front mounting bracket and bolts. Tighten all 4 mounting bolts gradually in a cross pattern. Torque mounting bolts to specification when available. Lower the transmission jack slightly to transfer weight to the mounts, then verify all bolts are secure.
13. 13

    Reconnect axle shafts
    Push each axle shaft inward to fully engage the splines with the differential side gears. Align the axle flange bolt holes with the differential yoke holes. Install all 8 bolts (4 per side) and tighten in a star pattern. Torque axle flange bolts to specification when available.
14. 14

    Reconnect driveshaft
    Position the rear driveshaft U-joint onto the differential pinion yoke, aligning the marks made during disassembly. Install the U-joint straps and all 4 strap bolts. Tighten bolts gradually in a cross pattern. Torque U-joint strap bolts to specification when available. Verify driveshaft rotates freely by hand.
15. 15

    Reconnect parking brake cable
    Reconnect the parking brake cable to the differential-mounted brake lever. Install the retaining clip to secure the cable end. Verify cable has proper slack and is not binding.
16. 16

    Install differential cover and fill with gear oil
    Clean the differential housing cover mating surface thoroughly with brake cleaner. Install a new gasket or apply a 1/8" bead of RTV silicone sealant around the cover perimeter. Position the cover on the housing and install all 10 cover bolts. Tighten bolts gradually in a star pattern. Torque cover bolts to specification when available. If using RTV, wait 15-20 minutes for initial cure before filling. Remove the differential fill plug (typically 3/8" or 1/2" square drive on passenger side of housing). Using a gear oil pump, fill the differential with 2.0 quarts of 75W-90 GL-5 gear oil until oil reaches the bottom of the fill hole. Reinstall fill plug and tighten securely.

Reassembly

1. Reinstall rear wheels and torque lug nuts to specification.
2. Lower vehicle from jack stands and remove all jacks.
3. Test parking brake engagement and adjustment.
4. Road test vehicle to verify proper differential operation, listening for abnormal noise or vibration.
5. After initial test drive (50-100 miles), recheck differential oil level and inspect cover for leaks.

Verification

• Verify all mounting bolts are tight and differential is secure in mounts.
• Confirm driveshaft phasing marks are aligned and U-joint bolts are torqued.
• Check differential oil level at fill plug - oil should be at bottom edge of fill hole.
• Verify no gear oil leaks from differential cover or pinion seal.
• Test drive vehicle and confirm smooth operation with no vibration or unusual noise from differential.
• Verify parking brake holds vehicle on incline.

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