Description and Operation — Power Transfer Unit — Overview

Power Transfer Unit

The Power Transfer Unit (PTU) is a gear reducer that is attached to the transmission. The PTU directs power from the transmission differential case through the dog clutch to the hypoid ring gear. The hypoid pinion gear is meshed with the ring gear and splined to the output flange. The dog clutch is used to transfer torque from the input shaft to the ring gear. When the dog clutch is released, torque is not transferred through the ring gear and pinion to the rear driveshaft. When the dog clutch is engaged, normal all-wheel drive operation is achieved by directing torque to the rear wheels as needed to prevent or control wheel slip and improve handling

Power Transfer Unit (PTU) External Components

Item	Part Number	Description
1	70347034	Breather tube.
2	W719766W719766	PTU to transmission bolt. Single use.
3	B500210B500210	Heat shield bolt
4	7F4697F469	Heat shield
5	W719768W719768	PTU to engine bracket bolts.
6	7B6647B664	PTU to engine bracket.
7	7B6967B696	Wiring harness bracket.
8	B500210B500210	Wiring harness bracket bolt.

Power Transfer Unit (PTU) Intermediate Shaft

Item	Part Number	Description
1	4B4224B422	Axle shaft retainer. Single use. Part of kit 4C198.
2	4C1994C199	Axle shaft to intermediate shaft D-ring. Single use. Use 4C197 (plastic assembly tool) to assemble this 4C199. Both parts are included in kit 4C198.
3	W719767W719767	Intermediate shaft bolt. Single use.
4	3B4703B470	Intermediate shaft bearing to PTU seal ring. Single use.
5	3K1833K183	Intermediate shaft.
6	—	Intermediate shaft seal. Serviced with the intermediate shaft.

Power Transfer Unit (PTU) Components

Item	Part Number	Description
1	63976397	Hollow dowels. Part of kit 7H469.
2	7L4867L486	PTU Housing. Carrier LH.
3	7A0217A021	Output Flange and Deflector. Part of kit 7275.
4	7G3607G360	Motor Actuator. Part of kit 7G360.
5	W790474W790474	Actuator Bolts. Part of kits 7P462 (seal kit) and 7G360 (actuator replacement kit).
6	7L4867L486	PTU Cover. Carrier RH.
7	12A64812A648	Oil Temperature Sensor
8	W790475W790475	PTU Housing to Cover Bolts. Part of kit 7R284.
9	4H2824H282	Drain Plug

Power Transfer Unit (PTU) Drive Motor

Item	Part Number	Description
1	—	Shift Fork.
2	—	Motor Actuator.
3	—	Gear reduction unit
4	—	Dog Clutch Collar
5	—	Actuator Cam

Power Transfer Unit (PTU) Internal Components

Item	Part Number	Description
1	48864886	Connecting Sleeve. Part of kit 7H469.
2	7B6527B652	PTU to Transmission Compression Seal. Single use. Dust seal for the cavity between the transmission and the PTU. Part of kit 7H469.
3	7A2837A283	Input Shaft Seal - LH. Single use. Isolates PTU brown fluid from leaking into the cavity between the transmission and the PTU. Part of kit 7H469.
4	—	Bearing Preload Selective Shim. Not serviceable.
5	—	Ring Gear Shaft Bearing - LH. Not serviceable.
6	—	Ring Gear Shaft. Not serviceable.
7	7P2507P250	O-Ring Cover. Single use. Seals PTU brown fluid from leaking at the housing-to-cover joint. Part of kit 7R284.
8	—	Ring Gear Shaft Bearing - RH. Not serviceable.
9	—	Dog Clutch Collar. Not serviceable.
10	—	Input Shaft. Not serviceable.
11	—	Input Shaft Bearing. Not serviceable.
12	7X4267X426	Input Shaft Seal - RH. Single use. Seals PTU brown fluid from leaking between the PTU and the RH axle shaft. Part of kit 7H469.
13	—	Input Shaft Bearing Snap Rings. Not serviceable.
14	—	Bearing Selective Shim. Not serviceable.
15	—	Collapsible Spacer. Not serviceable.
16	—	Output Shaft Nut. Not serviceable.
17	4B4224B422	Output Flange Snap Ring. Single use. Part of kit 7275.
18	7X4267X426	PTU Rear Seal. Single use. Seals PTU brown fluid from leaking between the housing and the output flange deflector. Part of kit 7H469.
19	—	Output Shaft Bearing. Not serviceable.
20	—	Output Shaft Bearing. Not serviceable.
21	—	Bearing Selective Shim. Not serviceable.
22	—	Output Shaft. Not serviceable.

Rear Seal Kit

Item	Part Number	Description
1	72757275	Companion Flange Kit
2	7X4267X426	Seal. Single use.
3	4B4224B422	Snap Ring. Single use.
4	—	Deflector. Part of 7A021.
5	7A0217A021	Flange and Deflector

RH Axle Shaft Kit

Item	Part Number	Description
	4C1984C198	RH Axle Shaft Kit
2	4C1974C197	Spline Protector. Used to install the axle shaft into the intermediate shaft D-ring.
3	4B4224B422	Snap Ring. Single use.
4	4C1994C199	Axle Shaft to Intermediate Shaft D-Ring. Single use.

Housing Seal Kit

Item	Part Number	Description
1	7P2847P284	Cover Seal Kit
2	W790475W790475	PTU Housing to Cover Bolts. Single use.
3	7P2507P250	O-Ring Cover. Single use. Seals PTU brown fluid from leaking at the housing-to-cover joint.

Actuator Seal Kit

Item	Part Number	Description
1	7P4627P462	Actuator Seal Kit
2	7P4617P461	Press the actuator to the cover at the gasket location. Single use. Prevents PTU brown fluid from leaking at the actuator-to-cover joint.
3	W790474W790474	Actuator Bolts. Single use. 4 required.

Input Shaft Seal Kit

Item	Part Number	Description
1	7X4697X469	Input Shaft Seal Kit
2	7X4267X426	RH Input Shaft Seal
3	7A2837A283	LH Input Shaft Seal
4	7B6527B652	PTU to Transmission Compression Seal
5	70867086	Input Shaft Connecting Sleeve with O-Ring
6	63976397	Hollow Dowels
7	48864886	Connecting Sleeve.
8	4B4224B422	Connecting Sleeve Snap Ring

Power Transfer Unit (PTU) Operation

The PTU has four (4) operating modes: Connected, Connecting, Disconnected, and Disconnecting. Each mode is controlled by the All-Wheel Drive Module. The PTU contains a reversible DC motor and two Hall-effect position sensors. The motor moves the shift fork, which engages or disengages the dog clutch. PTU Position Sensor A monitors the position of the actuator cam. PTU Position Sensor B monitors the position of the shift fork.

Connected Mode

Connected mode is the default mode for the PTU. The All-Wheel Drive Module commands Connected mode at the start of each key cycle. In Connected mode, the shift fork and dog clutch are positioned toward the right side of the PTU. The dog clutch is engaged. The driveshaft rotates at an increased speed compared to the front axle shafts. Torque is available at the RDU.

Connected Mode

To connect the PTU, the two halves of the dog clutch must be within 40 rpm of each other. The All-Wheel Drive Module calculates the speed difference based on the OSS, RDU driveshaft speed and the PTU gear ratio. The actuator motor is energized and rotates the actuator gear and actuator cam against the shift fork. When the dog clutch teeth are aligned, the cam pushes the shift fork into position and the clutch engages. It may take approximately 100–150 ms for the dog clutch to engage after the command is sent.

Disconnect Mode

The All-Wheel Drive Module controls Disconnected mode based on vehicle conditions. The purpose of Disconnected mode is to reduce drag losses from driveshaft rotation when conditions indicate all-wheel drive is not likely to be needed in the near future. In Disconnected mode, the shift fork and dog clutch are positioned toward the left or transmission side of the PTU. The dog clutch is disengaged.

Disconnect Mode

To disconnect the PTU, torque cannot be transmitted through the dog clutch. That is, the RDU must be fully disengaged. Depending on vehicle conditions, the All-Wheel Drive Module may keep the PTU engaged until the end of the key cycle. The actuator motor is energized and rotates the actuator gear and pulls the actuator cam away from the shift fork. When the dog clutch collar has moved far enough to the left or transmission side, the dog clutch teeth disengage.