308-07C Transfer Case - Vehicles With: 6-Speed Automatic Transmission - 6F35 2013 - 2014 MKZ
Diagnosis and Testing Procedure revision date: 08/23/2012

Transfer Case

Principles of Operation

The AWD system may be referred to as a 4WD system in other service information and owner literature or messages located on the message center.

The power transfer unit is a gearbox that is attached to the transmission. The RH intermediate shaft passes through the power transfer unit and engages the differential side gear as in normal FWD applications. The power transfer unit directs power to the rear driveshaft through a helical gear spline coupled to the transmission differential case, hypoid/helical ring gear assembly and pinion set. The power transfer unit is sealed from the transmission and has its own oil sump.

Serviceable components of the power transfer unit are limited to the output shaft seal and flange, intermediate shaft seal and deflector, input shaft seal, cover seal and the power transfer unit-transmission compression seal. The internal components are not serviced. Do not remove the cover of the power transfer unit. If any of the geared components, bearings, case cover or internal shafts are worn or damaged, a new power transfer unit must be installed.

Heat Protection Power Transfer Unit

During off-road operation or heavy trailer towing the AWD system may implement a heat protection mode to protect the power transfer unit from damage. The AWD system will reduce commanded torque to half as the temperature approaches its limit. Once the temperature limit is reached, then 2WD only is commanded.

For concerns with the AWD system or ATC ,
REFER to: Four-Wheel Drive Systems (308-07A Four-Wheel Drive Systems - Vehicles With: 6-Speed Automatic Transmission - 6F35, Diagnosis and Testing).

Inspection and Verification

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


  Visual Inspection Chart


Mechanical
  • Power transfer unit
  • Halfshafts and CV joints
  • Driveshaft and U-joints
  • Wheel/tire size and brand
  • Matching tire size and brand
  • Tire pressure


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

Symptom Chart

Diagnostics in this manual assume a certain skill level and knowledge of Ford-specific diagnostic practices.
REFER to: Diagnostic Methods (100-00 General Information, Description and Operation).

In most circumstances the PCM sets a DTC to help guide with diagnostics. Refer to the DTC Chart before using the Symptom Chart. The Condition column lists the vehicle condition. The Possible Sources column lists a detailed vehicle condition. The Action column lists the action to be performed to determine the cause of the condition. Each action lists the components that can cause the system and the individual components in that system. The components are listed in order of disassembly. Use the list of components and the required action to focus on disassembly inspections for the root cause of the concern.

Symptom Possible Sources Action
  • The power transfer unit makes noise
  • Tire inflation pressure
  • Tire and wheel size
  • Fluid level
  • Internal components
  • MAKE SURE all tires and wheels are the same size and brand and the inflation pressures are correct.
  • FILL with the correct type and amount of lubricant.
  • OPERATE the vehicle in all gears. If there is noise in the transmission in NEUTRAL, or in some gears and not in others, REMOVE and REPAIR the transmission.
    REFER to: Transmission (307-01B Automatic Transmission - Vehicles With: 6-Speed Automatic Transmission - 6F35, Removal).
    If there is noise in all gears, INSTALL a new power transfer unit. REFER to: Transfer Case (308-07C Transfer Case - Vehicles With: 6-Speed Automatic Transmission - 6F35, Removal).
  • Leaking fluid from the power transfer unit vent
  • Power transfer unit is over filled
  • Leaking automatic transmission fluid
  • Power transfer unit intermediate shaft seal
  • Power transfer unit compression seal
  • REFER to Analysis of Leakage.
  • Leaking gear lubricant from the seals
  • The power transfer unit vent is plugged (located on top of the power transfer unit)
  • Damaged seals
  • INSTALL a new power transfer unit.
    REFER to: Transfer Case (308-07C Transfer Case - Vehicles With: 6-Speed Automatic Transmission - 6F35, Removal).
  • Vehicle has no or inadequate torque at rear wheels
  • Rear axle
  • Power transfer unit mechanical failure

  • REFER to: Transfer Case (308-07C Transfer Case - Vehicles With: 6-Speed Automatic Transmission - 6F35, Removal).
  • Vehicle binds in a turn or resists turning/pulsates or shudders in a straight line
  • Wheels/tires
  • Brake system
  • Wheel bearings
  • Halfshafts
  • ABS system

  • REFER to: Brake System (206-00 Brake System - General Information, Diagnosis and Testing).

  • REFER to: Suspension System (204-00 Suspension System - General Information, Diagnosis and Testing).
  • Loss of AWD function or partial AWD function
  • Power transfer unit overheating
  • INSPECT the duct that cools the power transfer unit sump is free and clear of debris.

NOTE: Inspection of the seal's mating journal should be performed every time a seal is replaced. The mating part/journal should be replaced if it has any of the following conditions: Radial wear groove that is felt by running a finger nail across where the seal lip runs. Scratches, pitting, galling, nicks or other shaft damage under or near where the seal lip runs. Discoloration or coked oil on the shaft where the seal lip runs. Shaft corrosion under or near where the seal lip runs. Sharp edges or burrs on the shaft lead in chamfer. NEVER use emery cloth on journal finishes, replace the part.

Analysis of Leakage

The power transfer unit may leak different color fluids, automatic transmission fluid and a brown/black gear lube for power transfer unit fluid. The power transfer unit seals prevent these types of fluids from leaking. Its important to note the color of fluid leaking to determine the most appropriate service procedure.

NOTE: Remove and replace leaking seals using the information found in the Input Shaft Seal or Cover Seal replacement procedure. The specified tools called out in this procedure allows seal replacement without causing damage to the power transfer unit casing/drive gear.

Power Transfer Unit Leaks From the RH Side

If the leak is automatic transmission fluid, the power transfer unit linkshaft shaft seal needs to be replaced. This is outside on the RH side of the power transfer unit.
REFER to: Transfer Case Input Shaft Seal (308-07C Transfer Case - Vehicles With: 6-Speed Automatic Transmission - 6F35, Removal and Installation).

If the leak is brown/black gear lube, the power transfer unit larger cover seal needs to be replaced. This is located on the power transfer unit cover.

Power Transfer Unit Leaks From the LH Side

If the leak is automatic transmission fluid, the transmission seal needs to be replaced. This is in the transmission.
REFER to: Transfer Case (308-07C Transfer Case - Vehicles With: 6-Speed Automatic Transmission - 6F35, Removal).

If the leak is brown/black and venting fluid from the top of the power transfer unit, the power transfer unit is overfilled due to the input shaft seals leaking automatic transmission fluid into the power transfer unit. Replace the input shaft seals,
REFER to: Transfer Case Input Shaft Seal (308-07C Transfer Case - Vehicles With: 6-Speed Automatic Transmission - 6F35, Removal and Installation).



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