This procedure covers replacement of the transfer case encoder motor, which controls the 4WD mode selection on the BorgWarner electronic shift-on-the-fly transfer case.

Warnings

Tools required

Parts

• Transfer case encoder motor × 1 — Motorcraft YH-1851 or equivalent
• Transfer case encoder motor gasket/O-ring × 1 — Usually included with encoder motor

Fluids

• Motorcraft Transfer Case Fluid — 2.5 qt

Preparation

1. Park vehicle on level surface and engage parking brake
2. Place wheel chocks behind rear wheels
3. Allow transfer case to cool if vehicle was recently operated
4. Shift transfer case to 2H (two-wheel drive high) position using dash controls
5. Turn ignition to OFF and remove key
6. Raise front of vehicle and support securely on jack stands at frame rails
7. Remove driver side front wheel for better access if needed

Procedure

1. 1

   Access the transfer case encoder motor
   Locate the encoder motor on the driver side of the transfer case, toward the rear of the unit. It is a black plastic housing with an electrical connector on top. Remove any heat shields or splash guards that obstruct access using T30 Torx or 8mm bolts as applicable.
2. 2

   Disconnect electrical connector
   Press the locking tab on the encoder motor electrical connector and carefully pull straight out to disconnect. Inspect connector pins for corrosion or damage. Do not pull on wires, only on the connector body.
3. 3

   Position drain pan
   Place drain pan directly beneath the encoder motor location on the transfer case. When the encoder motor is removed, approximately 0.5 to 1 quart of transfer case fluid will drain from the opening.
4. 4

   Remove encoder motor mounting bolts
   Using a 10mm socket, remove the three mounting bolts securing the encoder motor to the transfer case housing. Keep bolts organized as they may be of different lengths. Support the encoder motor with one hand while removing the final bolt.
5. 5

   Remove encoder motor assembly
   Carefully pull the encoder motor straight out from the transfer case. The motor shaft engages with the mode shift fork inside the case. You may need to rotate the motor slightly while pulling to disengage. Allow fluid to drain into pan. Remove and discard the old gasket or O-ring from the transfer case mounting surface.
   ⚠Do not pry against the transfer case housing or encoder motor housing as both can crack
6. 6

   Inspect transfer case opening
   With the encoder motor removed, inspect the mode shift fork visible inside the transfer case opening for damage or wear. Check the mounting surface on the transfer case for cracks or damage. Clean the mounting surface thoroughly with a wire brush and shop towel to ensure proper gasket sealing.
7. 7

   Prepare new encoder motor
   Remove the new encoder motor from packaging. Verify it includes a new gasket or O-ring. Install the new gasket onto the encoder motor mounting flange, ensuring it seats properly in the groove. Apply a light coating of transfer case fluid to the O-ring to aid installation and prevent tearing.
8. 8

   Install new encoder motor
   Align the encoder motor shaft with the mode shift fork inside the transfer case. The shaft has a flat side that must align with the fork slot. Carefully push the encoder motor into the case while rotating slightly if needed to engage the shaft with the fork. Ensure the mounting flange is flush against the case housing before installing bolts.
   ⚠Do not force the encoder motor. If it does not seat easily, remove and check alignment of shaft with fork
9. 9

   Install mounting bolts
   Install the three mounting bolts finger-tight, ensuring the encoder motor remains properly seated. Tighten bolts in a star pattern to 10 Nm (89 lb-in), then final torque to specifications. Verify the motor housing sits flush against the transfer case with no gaps indicating gasket misalignment.
   Torque spec

   Mounting Bolts31 Nm (23 lb-ft)
10. 10

    Reconnect electrical connector
    Align the encoder motor electrical connector and push firmly until the locking tab clicks into place. Gently tug on the connector to verify it is fully locked.
11. 11

    Refill transfer case fluid
    Locate the transfer case fill plug on the passenger side of the case (may require access from the right side of vehicle). Remove fill plug using appropriate socket. Using a funnel with hose extension, add Motorcraft Transfer Case Fluid through the fill hole until fluid begins to drip from the opening. Reinstall fill plug and torque to specification. Total capacity is 2.5 quarts, but amount needed depends on how much drained during motor replacement.
12. 12

    Reinstall shields and wheel
    Reinstall any heat shields or splash guards removed for access. If the driver side front wheel was removed, reinstall and torque lug nuts in star pattern to specification. Do not fully torque lug nuts until vehicle weight is on the ground.
    Torque spec

    Wheel Lug Nuts140 Nm (103 lb-ft)

Reassembly

1. Ensure all electrical connections are fully seated and locked
2. Verify no tools or parts were left in the work area under the vehicle
3. Double-check that transfer case fill plug is properly installed and tightened
4. Lower vehicle from jack stands and remove wheel chocks
5. Final torque wheel lug nuts in star pattern with vehicle on ground if wheel was removed

Verification

• Start engine and let idle for 30 seconds
• With foot on brake, shift transfer case through all modes (2H, 4H, 4A if equipped, 4L) using dash controls, pausing 3-5 seconds in each mode
• Verify the 4WD indicator lights on the dash respond correctly to each mode selection
• Check for transfer case fluid leaks around the encoder motor mounting area
• Test drive vehicle and verify 4WD engagement works properly in both 4H and 4L ranges
• Recheck transfer case fluid level after test drive and top off if necessary

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