Ford Fusion: Power Transfer Unit - 6-Speed Automatic Transmission - 6F35 / Power Transfer Unit. Diagnosis and Testing

Operating Principles

The all-wheel drive system may be referred to as the AWD system in other service information and owner documentation, or in messages posted in the message center.

The transfer case is a gear unit bolted to the transmission. The right intermediate shaft passes through the transfer case and meshes with the differential side gear, as in a conventional front-wheel-drive layout. Applications: The transfer case delivers power to the rear propshaft through a splined helical gear connected to the transfer case housing, a hypoid/spiral bevel ring gear assembly, and a gear set. The transfer case is sealed from the transmission and has its own fluid sump.

Serviceable transfer case components are limited to the output shaft seal and output flange deflector, the intermediate shaft seal, the input shaft seal, the cover seal, and the transfer case-to-transmission compression seal. Internal components are not serviceable. If any transfer case gears, bearings, housing cover, or internal shafts are worn or damaged, install a new transfer case.

Transfer Case Thermal Protection

When driving off-road or towing a heavy trailer, the four-wheel-drive system may enter thermal protection mode to protect the powertrain from damage. The four-wheel-drive system will reduce the commanded torque by half as the temperature approaches its limit. Once the temperature limit is reached, only 2WD is commanded.

If there are concerns with the four-wheel-drive system or ATC,
REFER TO: Four-Wheel Drive Systems (308-07A Four-Wheel Drive Systems, Diagnosis and Testing).

Inspection and Verification

1
Verify the customer concern.
2
Visually inspect for obvious signs of mechanical damage.

Visual Inspection Chart

Power Transfer Unit
Axle Shafts and CV Joints
Driveshaft and Universal Joints
Wheel and Tire Size
Tire Size and Type Matching
Tire Pressure

1
If an obvious cause for the observed or reported concern is found, correct the cause (if possible) before proceeding to the next step.
2
If the cause is not visually apparent, verify the symptom and refer to the Symptom Chart.

Symptom Chart

The diagnosis in this manual assumes a certain level of skill and knowledge of Ford-approved diagnostic procedures.
REFER TO: Diagnostic Methods (100-00 General Information, Description and Operation).

In most cases, the PCM sets a DTC to aid in diagnosis. Refer to the DTC. Before using the Symptom Chart, the Condition column lists the vehicle condition. The Possible Sources column lists the specific vehicle components that may cause the condition. The Action column lists the actions to perform to determine the cause of the condition. Each action lists components that may cause the system fault and the individual components of that system. Components are listed in disassembly order. Use the component list and the required actions to focus on the disassembly checks for the root cause of the concern.

Symptom	Possible Sources	Action
Transfer Case Noise	Tire Pressure Tire and Wheel Size Fluid Level Internal Components	CHECK that all tires and wheels are the same size and brand, and that tire pressures are correct. FILL with the correct type and quantity of lubricant. DRIVE the vehicle in all gears. If there is transmission noise in NEUTRAL or in some gears and not others, REPAIR the transmission. REFER TO: Automatic Transmission — 2.7 L EcoBoost (238 kW/324 L hp) (307-01B Automatic Transmission — 6-Speed Automatic Transmission — 6F50/6F55, Diagnosis and Testing). If there is noise in all gears, INSTALL a new transfer case. REFER TO: Transfer Case (308-07B Transfer Case — 6-Speed Automatic Transmission — 6F35, Removal).
Transfer Case Valve Fluid Leak	Transfer Case Overfilled	CHECK the transfer case fluid level. REFER TO: Transfer Case Fluid Level Check (308-07B Transfer Case — 6-Speed Automatic Transmission — 6F35, General Procedures).
Automatic Transmission Fluid Leak	Power transfer unit intermediate shaft seal Transfer Case Compression Seal Transfer Case Intermediate Shaft Bushing	REFER TO Leak Diagnosis.
Transmission fluid leak from seals	Power transfer unit vent plugged (located at the top of the power transfer unit) Damaged seals	INSTALL a new transfer case vent. REFER TO: Transfer Case Vent (308-07B Transfer Case — 6-Speed Automatic Transmission — 6F35, Removal and Installation). REPLACE the leaking seal. REFER TO: Transfer Case Input Shaft Seal (308-07B Transfer Case — 6-Speed Automatic Transmission — 6F35, Removal and Installation). REFER TO: Transfer Case Rear Seal (308-07B Transfer Case — 6-Speed Automatic Transmission — 6F35, Removal and Installation). REFER TO: Transfer Case Intermediate Shaft Seal (308-07B Transfer Case — 6-Speed Automatic Transmission — 6F35, Removal and Installation).
Vehicle has no or insufficient torque at the rear wheels	Rear Axle Transfer Case Mechanical Malfunction	CHECK the rear drive axle for damage. REFER TO: Rear Drive Axle and Differential (205-02 Rear Drive Axle/Differential, Diagnosis and Testing). CHECK the transfer case for damage. REFER TO: Transfer Case (308-07B Transfer Case — 6-Speed Automatic Transmission — 6F35, Removal).
Vehicle binds in turns or resists turning/shudders or jerks in a straight line	Wheels/Tires Brake System Wheel bearings Half Shafts ABS system	CHECK the wheels and tires for damage. REFER TO: Wheels and Tires (204-04A Wheels and Tires, Diagnosis and Testing). CHECK the brake system for damage. REFER TO: Brake System (206-00 Brake System - General Information, Diagnosis and Testing). CHECK the suspension for damage. REFER TO: Suspension System (204-00 Suspension System — General Information, Diagnosis and Testing). CHECK the front half shafts for damage. REFER TO: Front Drive Half Shafts (205-04 Front Drive Half Shafts, Diagnosis and Testing). CHECK the ABS for damage. REFER TO: Anti-Lock Brake System (ABS) and Stability Control System (206-09 Anti-Lock Brake System (ABS) and Stability Control System, Diagnosis and Testing).
Loss of Four-Wheel Drive Function or Partial Four-Wheel Drive Operation	Transfer Case Overheating	CHECK that the transfer case cooling sump air duct is free of debris.

Leak Analysis

Different colored fluids may leak from the transfer case, including automatic transmission fluid and brown-black gear lubricant fluid. The transfer case seals prevent these fluid types from leaking. It is important to note the color of the leaking fluid to determine the most appropriate service procedure.

Power transfer unit leaking from the right side

If the leak is automatic transmission fluid, replace the intermediate shaft seal. It is located externally on the right side of the power transfer unit.
Refer to: Intermediate Shaft Seal (308-07B Power Transfer Unit - 6-Speed Automatic Transmission - 6F35, Removal and Installation).

If the leak is brown/black lubricant around the housing seam, the power transfer unit cover seal must be replaced. It is located on the power transfer unit cover.

Power transfer unit leaking from the left side

If the leak is automatic transmission fluid, the compression seal must be replaced.
Refer to: Power Transfer Unit (308-07B Power Transfer Unit - 6-Speed Automatic Transmission - 6F35, Removal).
Refer to: Intermediate Shaft Seal (308-07B Power Transfer Unit - 6-Speed Automatic Transmission - 6F35, Removal and Installation).

Power transfer unit leaking from the rear

If the leak is brown/black fluid, the flange/rear gear seal must be replaced.
Refer to: Transfer Case Rear Seal (308-07B Transfer Case - 6-Speed Automatic Transmission - 6F35, Removal and Installation).

Power transfer unit leaking from the upper vent

If a vent hose is present, check that the hose is not missing or disconnected.
Refer to: Power Transfer Unit Vent (308-07B Power Transfer Unit - 6-Speed Automatic Transmission - 6F35, Removal and Installation).
If the PTU vent hose is present and connected correctly, check the PTU fluid level. If the PTU fluid is overfilled, replace the intermediate shaft seal, the left input shaft seal and the right input shaft seal.
Refer to: Transfer Case Input Shaft Seal (308-07B Transfer Case - 6-Speed Automatic Transmission - 6F35, Removal and Installation).
Refer to: Intermediate Shaft Seal (308-07B Power Transfer Unit - 6-Speed Automatic Transmission - 6F35, Removal and Installation).