Electronic Shift Transfer Case

The transfer case is a Magna Powertrain 2-piece aluminum case transfer case design. Vehicles equipped with the 5R110 transmission include an aluminum adapter that fits between the transmission and transfer case assembly. The transfer case transfers engine power from the transmission to the front and rear axles. Under normal driving conditions, the unit is in 2H (4X2), but when desired, the operator may shift into 4H (4X4 HIGH) or 4L (4X4 LOW). 4H and 4L modes are intended for use in slippery conditions, such as ice and snow, or in off road situations only. 4H and 4L are not to be used on dry pavement. The ESOF transfer case is shifted electronically. The unit is lubricated by a positive displacement fluid pump that channels fluid flow through holes in the mainshaft. The encoder assembly used for mode indication is of a Hall effect type. The system uses a total of 4 independent transistors for mode recognition. Each transistor is associated with a specific range of motor movement. When the circuit to each transistor is closed, a ground path to any of the -A-, B-, C- or D- encoder pins is accomplished. When the circuit to each transistor is open, the connection to any of the -A-, B-, C- or D- encoder pins is pulled to voltage. Mode indication is "decoded" by the TCCM based on the varying combinations of signals coming from the transistors.

For a shift attempt from 2H to 4H or 4L, the following sequence occurs: 

• MSS is switched from 2H to 4H or 4L.
• For shift attempts into 4L:
  • transmission must be in NEUTRAL.
  • vehicle speed must be below 5 km/h (3 mph).
  • if the above 2 conditions are not met, the ESOF system does not attempt a shift and the IPC message center directs the driver to meet the appropriate shift conditions.
• gearmotor encoder assembly moves range fork in transfer case, which engages the dual-cone synchronizers.
• If a blocked shift condition occurs, the gearmotor encoder assembly performs 3 shift attempts (2H to 4H or 4H to 4L) with an approximate 1-second delay between each motor movement attempt.
  • If 2 complete shift sequences are unsuccessful (6 total shift attempts) during an ignition cycle and the MSS has not changed state, either DTC C1728:00 or C1729:00 is logged. These DTCs are only logged if the vehicle is moving above 5 km/h (3 mph) for at least 1 of the unsuccessful shift sequences.
• Generally, the transfer case engages upon vehicle movement as the probability of gear teeth blockage is greatly reduced while rolling. The IPC message center prompts the driver to pull forward during a blocked shift attempt to alleviate the gear teeth blockage that typically causes blocked shift attempts.
• If no gear teeth blockage is present, the transfer case dual-cone synchronizers bring the front driveline to the same speed as the rear driveline.
• The shift fork completes movement and the hublock vacuum solenoid supplies vacuum to the CVH system which couples the wheels to the front wheel driveline.
• Once the vacuum is supplied to the CVH system and the 4WD shift is completed, the appropriate 4WD indicator is displayed in the IPC message center.
  • The appropriate 4WD indicator is only displayed upon a successful 4WD system shift.

For a shift attempt from 4L or 4H to 2H, the following sequence occurs: 

• MSS is switched from 4H or 4L or 2H.
• For shift attempts into 4L:
  • transmission must be in NEUTRAL.
  • vehicle speed must be below 5 km/h (3 mph).
  • if the above 2 conditions are not met, the ESOF system does not attempt a shift and the IPC message center directs the driver to meet the appropriate shift conditions.
• Gearmotor encoder assembly moves range fork in transfer case, which disengages the dual-cone synchronizers.
• If a blocked shift condition occurs, the gearmotor encoder assembly performs 3 shift attempts (2H to 4H or 4H to 4L) with an approximate 1-second delay between each motor movement attempt.
  • If 2 complete shift sequences are unsuccessful (6 total shift attempts) during an ignition cycle and the MSS has not changed state, either DTC C1728:00 or C1729:00 is logged. These DTCs are only logged if the vehicle is moving above 5 km/h (3 mph) for at least 1 of the unsuccessful shift sequences.
• Generally, the transfer case disengages upon vehicle movement as the probability of gear teeth blockage is greatly reduced while rolling. The IPC message center prompts the driver to pull forward during a blocked shift attempt to alleviate the gear teeth blockage that typically causes blocked shift attempts.
• The shift fork completes movement and the hublock vacuum solenoid removes vacuum from the CVH system which uncouples the wheels to the front wheel driveline.
• Once the vacuum is removed from the CVH system and the 4WD shift is completed, the appropriate 4WD indicator is displayed in the IPC message center.
  • The appropriate 4WD indicator is only displayed upon a successful 4WD system shift.