Reduction Gear Service

Service and replacement of the reduction gear assemblies in the front and/or rear drive units of the Rivian EDV 500, including fluid drain, gear inspection, and refill with proper EV transmission fluid.

Warnings

Tools required

Parts

• Front drive unit reduction gear assembly × 1 — Use OEM specification
• Rear drive unit reduction gear assembly × 1 — Use OEM specification
• Drive unit drain plug washer × 2 — Use OEM specification
• Drive unit fill plug O-ring × 2 — Use OEM specification
• Drive unit mounting bolts × 1 — Use OEM specification
• Output shaft seal × 2 — Use OEM specification
• Drive unit gasket/seal kit × 1 — Use OEM specification

Fluids

• EV Transmission Fluid — 10 qt

Preparation

1. Park vehicle on level surface and engage parking brake
2. Verify high-voltage battery state of charge is below 30% or follow Rivian HV isolation procedures
3. Disconnect 12V auxiliary battery negative terminal and wait 5 minutes for system capacitor discharge
4. Access high-voltage service disconnect (located under rear cargo area) and remove service plug per Rivian service manual
5. Install high-voltage lockout device and attach safety tag
6. Use Rivian diagnostic tool to verify high-voltage system is fully isolated (0V at service disconnect)
7. Lift vehicle to working height and secure on jack stands at designated lift points
8. Remove all four wheels to access drive unit mounting hardware
9. Remove underbody panels and splash shields to expose front and rear drive units
10. Allow drive units to cool to ambient temperature if vehicle was recently operated (minimum 2 hours)
11. Place absorbent pads under drive units to catch fluid spillage

Procedure

1. 1

   Drain existing transmission fluid
   Position drain pan under front drive unit. Locate drain plug on bottom of drive unit housing (14mm hex). Remove drain plug and allow fluid to drain completely (approximately 1.5 quarts per unit). Inspect drained fluid for metallic debris or discoloration indicating gear wear. Repeat process for rear drive unit. Remove and inspect drain plug washers for damage.
2. 2

   Disconnect drive axles
   Mark orientation of axle flanges to drive unit output flanges for proper reassembly. Remove axle flange bolts (typically 6 bolts per side). Support axles with wire or straps to prevent damage to CV joints. Do not allow axles to hang unsupported by their own weight.
3. 3

   Disconnect electrical connectors
   Locate motor temperature sensor connectors, resolver/encoder connectors, and motor phase connectors on drive unit housing. Release connector locks and carefully disconnect all electrical connections. Label each connector with position tape for correct reinstallation. Secure connectors away from work area.
4. 4

   Disconnect cooling lines
   Identify coolant inlet and outlet lines connected to drive unit motor cooling jacket. Place drain pan to catch residual coolant (expect 1-2 quarts per unit). Release quick-disconnect fittings or remove hose clamps. Cap or plug open coolant lines immediately to prevent contamination.
5. 5

   Support and remove drive unit
   Position transmission jack or support fixture under drive unit with proper contact points on unit housing (not on motor cover). Remove drive unit mounting bolts while supporting full weight with jack. Typical mounting includes 4-6 bolts to subframe or chassis rails. Carefully lower drive unit and remove from vehicle. Note: Each drive unit weighs approximately 150-200 lbs.
6. 6

   Remove motor from gear housing
   With drive unit on workbench, remove motor housing-to-gear housing bolts (typically 8-12 bolts around perimeter). Carefully separate motor assembly from reduction gear housing using plastic pry tools if needed. The rotor will remain magnetically attracted to the stator—pull straight out to avoid damage. Set motor assembly aside in clean area.
7. 7

   Disassemble reduction gear assembly
   Remove gear housing cover bolts and carefully separate cover. Extract reduction gear assembly noting orientation of all components. Remove input gear (connected to rotor shaft), intermediate gears if present, and output gear/differential assembly. Inspect all gear teeth for wear, pitting, or damage. Check bearings for roughness or play. Measure gear backlash and compare to factory specifications.
8. 8

   Clean and inspect housing
   Thoroughly clean gear housing interior with approved EV-safe solvent. Inspect housing for cracks, especially around bearing bores and bolt holes. Check all bearing races for wear or damage. Inspect housing sealing surfaces for scratches or imperfections. Clean and inspect all bolt threads.
9. 9

   Install new reduction gear assembly
   Apply thin coat of EV transmission fluid to all gear teeth and bearing surfaces. Install new reduction gear components in reverse order of removal, ensuring proper orientation and alignment. Install intermediate gears with correct mesh pattern. Install output gear/differential assembly ensuring bearings are properly seated in housing bores. Verify all components rotate smoothly without binding.
10. 10

    Reassemble gear housing
    Apply new gasket or approved sealant to housing mating surface per Rivian specifications. Carefully install gear housing cover ensuring no pinching of gasket. Install and hand-tighten all housing bolts in star pattern. Final torque housing bolts per factory specification (not provided in database—consult Rivian service information).
11. 11

    Reinstall motor to gear housing
    Inspect motor rotor-to-gear input shaft splines for damage. Apply small amount of anti-seize to spline contact areas. Carefully align motor assembly with gear housing, ensuring rotor splines engage properly with input gear. The magnetic attraction will pull components together—control this motion carefully. Install motor housing bolts and torque in star pattern per factory specification.
12. 12

    Install new output shaft seals
    Remove old output shaft seals using seal puller or pick. Clean seal bore thoroughly. Install new seals using appropriately sized seal driver, ensuring seals are seated squarely and to proper depth. Apply thin coat of EV transmission fluid to seal lips before installation.
13. 13

    Reinstall drive unit in vehicle
    Lift drive unit into position using transmission jack. Align mounting points with subframe/chassis rails. Install mounting bolts and hand-tighten. Verify drive unit is properly positioned and axle output flanges align with axle shafts. Torque mounting bolts per factory specification in proper sequence.
14. 14

    Reconnect all connections
    Reconnect coolant lines ensuring proper seating of quick-disconnect fittings or secure hose clamps. Reconnect all electrical connectors matching labeled positions from disassembly. Verify all connector locks are fully engaged. Reconnect drive axles to output flanges, aligning marks made during disassembly. Install and torque axle flange bolts per specification.
15. 15

    Fill drive units with transmission fluid
    Install new drain plug washers and reinstall drain plugs (torque per specification if available). Locate fill plug on side of drive unit housing. Remove fill plug and O-ring. Using fluid transfer pump, fill drive unit with EV transmission fluid until fluid begins to flow from fill opening. Allow to settle and top off as needed. Install new fill plug O-ring and reinstall fill plug. Front unit requires approximately 1.5 quarts, rear unit approximately 2.0 quarts. Total system capacity is 10.0 quarts including lines and cooler.

Reassembly

1. Install all underbody panels and splash shields removed during disassembly
2. Reinstall all four wheels and torque lug nuts to specification
3. Reconnect 12V auxiliary battery negative terminal
4. Fill cooling system to proper level with EV battery/motor coolant if coolant was drained
5. Reinstall high-voltage service disconnect plug and verify proper seating
6. Remove lockout/tagout devices

Verification

• With vehicle still lifted, power on vehicle and verify no warning lights related to drive system
• Use Rivian diagnostic tool to verify drive unit temperature sensors are reading properly
• Check for fluid leaks around drain plugs, fill plugs, output seals, and housing gaskets
• Perform drive unit recalibration procedure using Rivian diagnostic software
• Clear any fault codes related to HV disconnect and verify all systems show ready status
• Lower vehicle and perform test drive starting with low-speed maneuvers in parking area
• Verify smooth operation with no abnormal noises, vibrations, or warning messages
• Test all-wheel drive engagement and torque vectoring functionality
• After test drive, re-lift vehicle and inspect for any fluid leaks
• Verify drive unit fluid levels again after heat cycling—top off if needed
• Final diagnostic scan to confirm no fault codes present

More procedures for this vehicle