Replace the differential pinion seal on the front or rear drive unit to address fluid leaks from the pinion shaft area.

Warnings

Tools required

Parts

• Differential pinion seal (front or rear) × 1 — Use OEM Rivian specification
• Pinion flange nut × 1 — Use OEM specification - one-time use
• Drive shaft mounting bolts × 4 — Use OEM specification if reuse not permitted
• Differential cover gasket or RTV sealant × 1 — Use OEM specification

Fluids

• 75W-90 GL-5 Gear Oil — 2 qt

Preparation

1. Verify which differential (front or rear) requires pinion seal replacement by inspecting for fluid leakage at the pinion flange area
2. Place vehicle on level ground and engage parking brake
3. Disable high-voltage system following Rivian service procedures and install lockout/tagout devices
4. Raise vehicle on lift or jack stands at manufacturer-specified lift points ensuring vehicle is stable
5. Place wheel chocks at opposite end of vehicle from differential being serviced
6. Remove wheel and tire assembly on side providing best access to drive shaft
7. Place drain pan under differential to catch gear oil
8. Allow differential to cool to ambient temperature if vehicle was recently driven

Procedure

1. 1

   Mark and measure pinion bearing preload
   Using an inch-pound torque wrench on the pinion flange nut, measure and record the rotational torque required to turn the pinion (typically 15-25 in-lbs with seals installed). This is critical for reassembly. Mark the pinion flange position relative to the pinion shaft with paint or punch marks to maintain orientation.
2. 2

   Remove drive shaft from differential
   Mark the drive shaft flange to pinion flange orientation for proper reassembly phasing. Remove the four drive shaft mounting bolts at the differential pinion flange. Support the drive shaft and secure it out of the way using wire or bungee cords. Do not allow drive shaft to hang unsupported as this can damage CV joints.
3. 3

   Drain differential fluid
   Remove the differential drain plug (if equipped) or remove the differential cover to drain gear oil into the drain pan. If removing cover, note the position of any alignment dowels. Allow fluid to drain completely. Inspect drained fluid for metal debris or contamination which may indicate internal differential damage.
4. 4

   Remove pinion flange nut
   Using the pinion flange holding tool to prevent rotation, remove the pinion flange nut with an impact wrench or breaker bar. Note that this nut is typically torqued to 150-250 ft-lbs. Discard the nut as it is a one-time use torque-to-yield fastener on most Rivian drive units.
5. 5

   Remove pinion flange
   Using a pinion flange puller or suitable two-jaw puller, carefully remove the pinion flange from the pinion shaft. Note the position of any shims, spacers, or washers behind the flange and keep them in order for reassembly. Do not pry on the flange as this can damage sealing surfaces.
6. 6

   Remove old pinion seal
   Using a seal puller or seal removal tool, carefully extract the old pinion seal from the differential housing. Take care not to damage the seal bore surface in the housing. Inspect the seal bore for gouges, burrs, or corrosion that could cause the new seal to leak.
7. 7

   Inspect pinion shaft and flange
   Thoroughly inspect the pinion shaft seal surface and the pinion flange inner seal contact area for wear grooves, scoring, or corrosion. Minor imperfections can be polished with fine emery cloth, but deep grooves require component replacement. Verify the pinion flange is not damaged or bent.
8. 8

   Install new pinion seal
   Lightly coat the outer diameter of the new pinion seal with gear oil. Using the appropriate size seal driver from your installation set, carefully drive the new seal into the housing bore, ensuring it seats evenly and to the proper depth (flush with housing face or slightly recessed per service manual). Apply a light coat of gear oil to the seal lip.
9. 9

   Reinstall pinion flange
   Install any shims, spacers, or washers that were removed in their original positions. Align the pinion flange with the reference marks made during disassembly and carefully slide it onto the pinion shaft. Ensure the flange seats fully against the spacer or bearing.
10. 10

    Install new pinion flange nut and set preload
    Apply medium-strength thread locker to the threads of the new pinion flange nut. Thread the nut onto the pinion shaft by hand. Using the flange holding tool and torque wrench, tighten the nut gradually while checking rotational torque frequently with the inch-pound torque wrench. Tighten until rotational torque matches the original measurement from Step 1 (typically 15-25 in-lbs). Note: Without service manual torque specifications, you must match the original preload measurement. Over-tightening will damage bearings; under-tightening will cause premature seal failure.
11. 11

    Refill differential with gear oil
    If differential cover was removed, install new gasket or apply RTV sealant per manufacturer specifications and reinstall cover. Using a fluid pump or fill bottle, add the appropriate amount of 75W-90 GL-5 gear oil through the fill plug: 1.5 quarts for front differential or 2.0 quarts for rear differential. Fill until oil reaches the bottom of the fill plug opening. Install and tighten fill plug.
12. 12

    Reinstall drive shaft
    Align the reference marks made during disassembly and position the drive shaft flange to the pinion flange. Apply thread locker to the four drive shaft mounting bolts and install them. Tighten bolts in a cross pattern to ensure even seating. Note: Torque specifications not available in database - follow manufacturer service manual.

Reassembly

1. Double-check that all fasteners are properly tightened and no tools or parts are left in the work area
2. Reinstall wheel and tire assembly if removed
3. Lower vehicle to ground and perform final torque check on wheel lug nuts
4. Remove high-voltage lockout/tagout devices and restore vehicle to operational status per Rivian procedures

Verification

• Start vehicle and verify no warning lights related to drivetrain are illuminated
• Rotate pinion by hand (if accessible) to verify smooth rotation with proper resistance
• Inspect pinion seal area for any signs of gear oil leakage immediately after refilling
• Test drive vehicle in both forward and reverse, exercising the differential through various loads
• After test drive, re-inspect pinion seal area and check differential fluid level to ensure no leaks are present
• If available, verify differential fluid temperature sensor is reading normally on vehicle diagnostics
• Perform final leak inspection after 50-100 miles of driving

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