Replace the shift fork in the electric drive unit (EDU) reduction gearbox, requiring complete EDU disassembly and internal component access.

Warnings

Tools required

Parts

• Shift fork assembly × 1 — Use OEM specification
• EDU gasket kit × 1 — Use OEM specification
• Output shaft seal × 1 — Use OEM specification
• Drain plug washer × 1 — Use OEM specification
• Fill plug washer × 1 — Use OEM specification
• Transmission pan gasket or sealant × 1 — Use OEM specification
• Transmission drain plug crush washer × 1 — Use OEM specification

Fluids

• ACDelco Dexron VI ATF — 14 qt

Preparation

1. Verify customer concern and document any diagnostic trouble codes using GM MDI 2 scan tool
2. Verify high voltage system is disabled: Turn off vehicle, remove 12V battery negative cable, wait 5 minutes, verify HV system is de-energized with appropriate meter
3. Install high voltage lockout/tagout device per GM service procedures
4. Raise vehicle on lift and secure with safety locks
5. Remove front wheels and lower vehicle splash shields
6. Place drain pan under EDU and remove drain plug with new washer ready for reinstallation
7. Allow complete fluid drainage (approximately 30 minutes)
8. Remove front subframe and disconnect all electrical connectors from motor and EDU
9. Support EDU with transmission jack and remove all mounting bolts
10. Carefully lower EDU from vehicle and transfer to clean workbench with adequate lighting

Procedure

1. 1

   Remove EDU cover and external components
   Clean exterior of EDU thoroughly. Remove all cover screws in a criss-cross pattern. Carefully separate cover from housing using plastic dead blow hammer if necessary. Remove position sensors and any external brackets. Mark sensor positions for reinstallation.
   Torque spec

   Cover Screws11 Nm (8 lb-ft)

   Sensor Bolts11 Nm (8 lb-ft)
2. 2

   Document and measure gear positions
   Before disassembly, use dial indicator to measure gear endplay and backlash. Record all measurements. Take photos of all component positions, shim locations, and orientation marks. These measurements are critical for proper reassembly.
3. 3

   Remove rotor assembly
   If equipped with park pawl mechanism, release pawl spring tension carefully. Remove flywheel bolts in reverse star pattern sequence. The rotor assembly is very heavy - use appropriate lifting equipment or assistance. Place rotor on clean padded surface to prevent damage to windings.
   ⚠Rotor assembly weighs over 40 lbs and contains strong permanent magnets. Keep away from electronic devices and pacemakers.
   Torque spec

   Flywheel Bolts95 Nm (70 lb-ft)
4. 4

   Remove gearbox pan and access internal components
   Remove pan bolts in proper sequence (outside to inside pattern). Carefully separate pan from case - residual fluid will drain. Clean all mating surfaces thoroughly. Inspect internal components for wear or damage. Document any abnormal wear patterns for root cause analysis.
   Torque spec

   Pan Bolts16 Nm (12 lb-ft)
5. 5

   Access shift fork mechanism
   Locate shift fork assembly within gearbox. On Bolt EUV EDU, the shift fork controls park position engagement. Remove retaining snap rings using internal snap ring pliers. Note the position of any detent springs or balls. Keep all small components organized and clean.
6. 6

   Remove shift fork assembly
   Carefully slide shift fork off its shaft, noting engagement position with gear collar. Inspect shaft for wear, scoring, or discoloration. Check fork contact pads for excessive wear. If shaft shows damage, it must also be replaced. Remove shaft if necessary by removing retaining clips or bolts.
   ⚠Shift fork spring may be under tension. Control release to prevent component loss or injury.
7. 7

   Inspect and prepare for new shift fork installation
   Clean shift fork shaft thoroughly with lint-free towels and approved solvent. Inspect gear collar engagement surface for wear or damage. Measure collar bore if tools available. Compare new shift fork to old unit to verify correct replacement part. Check new fork pads for proper contact geometry.
8. 8

   Install new shift fork assembly
   Lightly lubricate shift fork shaft with Dexron VI ATF. Install new shift fork onto shaft in documented orientation. Verify fork engagement pads align properly with gear collar groove. Install retaining snap rings ensuring they seat fully in grooves. Verify fork moves smoothly through full range of motion without binding.
9. 9

   Reassemble gearbox internal components
   Install any shims or spacers in original positions per documentation. Verify all bearings are properly seated. Check gear endplay measurements against specifications. Install new pan gasket or apply appropriate RTV sealant per GM specifications. Allow sealant to set per manufacturer instructions if applicable.
10. 10

    Install gearbox pan and rotor assembly
    Install pan and torque pan bolts in criss-cross pattern from center outward. Clean rotor and stator mating surfaces. Carefully align and install rotor assembly onto stator, ensuring no contact with windings. Install flywheel bolts hand-tight initially, then torque in proper star pattern sequence.
    Torque spec

    Pan Bolts16 Nm (12 lb-ft)

    Flywheel Bolts95 Nm (70 lb-ft)
11. 11

    Install EDU cover and sensors
    Install new cover gasket or apply sealant as specified. Position cover ensuring proper alignment with dowel pins. Install cover screws and torque in criss-cross pattern. Reinstall all position sensors to documented locations and torque sensor bolts. Verify no wiring is pinched.
    Torque spec

    Cover Screws11 Nm (8 lb-ft)

    Sensor Bolts11 Nm (8 lb-ft)
12. 12

    Reinstall EDU into vehicle
    Clean EDU mounting surfaces on subframe. Position EDU on transmission jack and raise into position. Install all mounting bolts hand-tight, then torque to specification in proper sequence. Reconnect all electrical connectors ensuring positive engagement. Reinstall subframe components and front suspension.
    Torque spec

    Mounting Bolts61 Nm (45 lb-ft)
13. 13

    Fill EDU with fresh fluid
    Ensure drain plug is installed with new washer and torqued to specification. Locate fill plug on EDU case. Using fluid pump, add approximately 13.5 quarts of ACDelco Dexron VI ATF through fill hole until fluid reaches bottom of fill plug opening. Install fill plug with new washer and torque to specification.
    ℹ️Fill capacity may vary slightly. Fill until fluid begins to drip from fill hole with vehicle level.
    Torque spec

    Drain Plug34 Nm (25 lb-ft)

    Fill Plug34 Nm (25 lb-ft)
14. 14

    Remove HV lockout and perform system checks
    Reinstall front wheels, splash shields, and lower vehicle. Reconnect 12V battery negative cable. Remove high voltage lockout device per GM procedures. Using GM MDI 2, clear any stored codes and perform EDU relearn procedure. Verify no active DTCs present.

Reassembly

1. All gaskets and seals must be replaced - never reuse
2. Torque all fasteners to specified values in proper sequence
3. Fill EDU to proper level with fresh ACDelco Dexron VI ATF only
4. Perform high voltage system integrity check before releasing vehicle
5. Road test vehicle to verify proper operation and recheck for leaks

Verification

• Using scan tool, verify no DTCs present and all EDU parameters are within normal range
• Test drive vehicle and verify smooth operation through all drive modes (Drive, Low, Reverse)
• Verify park pawl engages and releases properly - vehicle should not roll in Park position
• Check for fluid leaks around all EDU seals, plugs, and cover after test drive
• Verify EDU fluid level is correct after vehicle reaches operating temperature
• Perform final high voltage system check and verify all lockout devices removed
• Document repair in vehicle service history with mileage and parts used

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