Reduction Gear Service

This procedure covers the removal, inspection, and replacement of the reduction gear assemblies on the front and/or rear electric drive units of the 2024 Rivian EDV 500.

Warnings

Tools required

Parts

• Reduction gear assembly (front or rear as needed) × 1 — Use OEM specification
• Drive unit gasket set × 1 — Use OEM specification
• Output shaft seal × 1 — Use OEM specification
• Reduction gear bearing set × 1 — Use OEM specification
• Drain plug washer × 2 — Use OEM specification
• Fill plug O-ring × 1 — Use OEM specification

Fluids

• EV Transmission Fluid — 10 qt
• EV Battery/Motor Coolant — 2 qt

Preparation

1. Park vehicle on level surface and engage parking brake
2. Use Rivian diagnostic tool to place vehicle in service mode and disable high voltage system
3. Disconnect 12V auxiliary battery negative terminal
4. Raise and securely support vehicle on lift or jack stands at manufacturer-specified lift points
5. Remove underbody panels and belly pan to access electric drive unit
6. Mark driveshaft-to-differential flange orientation for reassembly alignment
7. Place wheel chocks on opposite axle if working on one end only
8. Verify high voltage interlock is removed and orange safety plug is disconnected
9. Photograph or document all electrical connector routing and positions
10. Allow drive unit to cool to ambient temperature if vehicle was recently driven

Procedure

1. 1

   Drain drive unit fluids
   Position drain pan under the electric drive unit. Remove the EV transmission fluid drain plug and allow fluid to drain completely (approximately 10 quarts). Remove the coolant drain plug if equipped on the motor housing and drain coolant (approximately 2 quarts). Inspect drained fluid for metal contamination or unusual discoloration which may indicate bearing or gear damage.
2. 2

   Disconnect electrical connections
   Disconnect all electrical connectors from the drive unit including motor phase cables, resolver/encoder connectors, temperature sensors, and inverter connections. Tag or label each connector with its position. Remove any wire harness brackets or clips securing cables to the drive unit housing. Support harnesses to prevent strain on connectors.
3. 3

   Remove coolant lines
   Disconnect coolant supply and return lines from the motor housing. Have drain pan positioned as residual coolant will drain. Cap or plug all coolant ports immediately to prevent contamination. Remove coolant line mounting brackets from drive unit housing.
4. 4

   Disconnect halfshafts or driveshaft
   Remove the halfshaft-to-hub bolts (if servicing front drive unit) or mark and disconnect the driveshaft from the differential flange (if servicing rear drive unit). Support halfshafts or driveshaft to prevent damage to CV joints or boots. If removing halfshafts completely, note the installed depth of the splined end in the differential.
5. 5

   Support and remove drive unit
   Position electric drive unit support fixture or transmission jack under the drive unit. Secure the unit to the support fixture. Remove all drive unit mounting bolts and brackets connecting it to the subframe or motor mounting points. Carefully lower the drive unit while guiding electrical connections and coolant lines clear. Place drive unit on clean workbench.
6. 6

   Separate inverter and motor housing
   With drive unit on workbench, remove fasteners securing the inverter assembly to the motor housing. Carefully separate the inverter, noting the position of any alignment dowels or gaskets. Set inverter aside in a clean, safe location. Remove the motor housing cover bolts and separate the motor housing from the reduction gear housing, using plastic pry tools if necessary to break the gasket seal.
7. 7

   Remove motor rotor assembly
   The motor rotor is integrated with or connected to the input shaft of the reduction gear. Carefully withdraw the rotor assembly from the stator, taking care not to damage the stator windings or rotor magnets. Support the rotor weight evenly and place on padded surface. Note the orientation of any alignment marks between rotor and input shaft.
8. 8

   Access reduction gear assembly
   Remove remaining fasteners securing the reduction gear housing sections together. Carefully separate the housing halves using plastic pry tools in designated pry points only. The reduction gear assembly includes the input gear (connected to motor), intermediate gears (if applicable), and output gear/differential. Inspect housing interior for debris, metal shavings, or scoring.
9. 9

   Remove and inspect reduction gears
   Remove the reduction gear assembly components in order: output shaft with gear, intermediate shaft(s) with gears if present, and input shaft gear. Keep all shims, spacers, and bearing races with their respective components. Measure and record all shim thicknesses. Inspect all gear teeth for pitting, scoring, excessive wear, or chipping. Inspect all bearings for roughness, pitting, or discoloration. Measure gear backlash and bearing preload specifications using dial indicator. Replace any worn or damaged components.
10. 10

    Remove bearings and seals
    Using appropriate bearing pullers, remove all bearings from shafts and bearing races from housings. Remove output shaft seal using seal puller. Mark or document the orientation and position of each bearing and race. Inspect bearing bores in housing for wear, scoring, or out-of-round conditions. Clean all bearing surfaces and bores thoroughly with solvent and lint-free cloths.
11. 11

    Install new bearings and components
    Press new bearing races into housing bores ensuring they are fully seated and square. Install new bearings onto shafts using press or bearing installer with proper drivers. Apply light coating of EV transmission fluid to bearing surfaces. Install shims in their original positions (or adjusted positions if backlash/preload measurements require changes). Apply thread locker to all fastener threads per service manual specifications.
12. 12

    Reassemble reduction gear assembly
    Install input shaft with gear into housing, ensuring bearings are properly seated. Install intermediate gears if applicable, verifying correct mesh with input gear. Install output shaft assembly with differential (if integrated). Check gear mesh pattern by applying marking compound to gear teeth and rotating assembly through several revolutions. Verify proper contact pattern across gear tooth faces. Measure and verify gear backlash is within specification using dial indicator.
13. 13

    Assemble gear housing
    Apply new gasket or gasket maker to housing mating surfaces per manufacturer specifications. Carefully join housing halves, ensuring all components remain properly aligned and no gears bind. Install and hand-tighten all housing fasteners, then torque in proper sequence working from center outward. Rotate output shaft by hand to verify smooth operation with no binding or excessive noise.
14. 14

    Reinstall motor rotor and housing
    Carefully install motor rotor back into stator, aligning any reference marks made during disassembly. Ensure rotor magnets do not contact stator windings during installation. Install new gasket on motor housing mating surface. Reinstall motor housing cover and torque fasteners in proper sequence. Reinstall inverter assembly with new gasket or thermal interface material as specified, and secure with fasteners.
15. 15

    Install drive unit and reconnect components
    Raise drive unit into position using support fixture, aligning mounting points with subframe or chassis mounting locations. Install and torque all drive unit mounting fasteners. Reconnect halfshafts or driveshaft, aligning reference marks made during disassembly. Reconnect all coolant lines with new O-rings or seals. Reconnect all electrical connectors, ensuring positive engagement and proper routing. Install new drain plug washers and install drain plugs finger-tight.

Reassembly

1. Torque drain plug to specification and verify sealing washer is properly seated
2. Fill drive unit with fresh EV transmission fluid (10 quarts) through fill port using fluid pump until fluid reaches bottom of fill hole
3. Fill coolant system with fresh EV battery/motor coolant (2 quarts) and bleed air from system per manufacturer procedure
4. Install fill plug with new O-ring and torque to specification
5. Reinstall underbody panels and belly pan with all fasteners
6. Reconnect 12V auxiliary battery negative terminal
7. Verify all electrical connectors are fully seated and locked
8. Double-check all fasteners are installed and properly torqued

Verification

• With vehicle still raised, use Rivian diagnostic tool to exit service mode and reactivate high voltage system per manufacturer procedure
• Perform drive unit initialization and motor phase learning procedure using diagnostic tool
• Check for any diagnostic trouble codes and clear if related to service performed
• With wheels off ground, place vehicle in drive and verify smooth rotation of wheels at low speed with no unusual noise or vibration
• Check all fluid levels and inspect for leaks around drain plug, fill plug, seals, and coolant connections
• Lower vehicle and perform test drive at various speeds, verifying smooth acceleration, deceleration, and no abnormal noises or vibrations
• Re-check fluid levels after test drive with vehicle on level surface
• Verify no warning lights or error messages on instrument cluster
• Perform final inspection of all connections and fasteners
• Document service in vehicle maintenance records including any shim changes or measurements taken

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