Power Transfer Unit (PTU)

Principles of Operation

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

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

Heat Protection Mode

During very extreme off-road operation, the AWD system utilizes a heat protection mode to protect the ATC solenoid (part of rear axle) from damage. If the system detects an overheat condition, it enters a locked mode. If the heat in the system continues to rise once in the locked mode, the 4X4 control module disables the ATC solenoid. Allow the system to cool down at least 10 minutes with the ignition switch in the ON position.

For concerns with the 4X4 control module or ATC , refer to Section 308-07A .

Inspection and Verification

1. Verify the customer concern.

2. Inspect for obvious signs of mechanical damage.

  Visual Inspection Chart

3. If an obvious cause for an observed or reported concern is found, correct the cause (if possible) before proceeding to the next step.

4. If the cause is not visually evident, verify the symptom and GO to Symptom Chart .

Symptom Chart

Diagnostics in this manual assume a certain skill level and knowledge of Ford-specific diagnostic practices. Refer to Diagnostic Methods in Section 100-00 for information about these practices.

Analysis of Leakage

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 can be 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.

The PTU may leak different color fluids, red oil leak for an automatic transmission fluid and brown/black gear lube for PTU fluid. The PTU seals prevent these types of fluids from leaking. Its important to note the color fluid that is leaking to determine the most appropriate service procedure.

PTU Leaks From the RH Side

NOTICE: Remove and replace leaking seals using the information found in the Intermediate Shaft Seal and Deflector or Cover Seal replacement procedure. The specified tools called out in this procedure will allow seal replacement without causing damage to the PTU casing/drive gear.

If the leak is red automatic transmission fluid, the PTU intermediate shaft seal needs replacement. This is inside the bore of the PTU shaft behind the deflector. REFER to the Intermediate Shaft Seal and Deflector .

If the leak is brown/black gear lube, the PTU larger cover seal needs replacement. This is located on the PTU cover behind the deflector. REFER to Cover Seal .

PTU Leaks From the LH Side

If the leak is red automatic transmission fluid, the compression seal needs replacement. This is between the PTU and transmission. REFER to Power Transfer Unit (PTU) — 3.5L or Power Transfer Unit (PTU) — 3.5L GTDI .

If the leak is brown/black and venting fluid from the top of the PTU , the PTU is overfilled due to the input shaft seals leaking red automatic transmission fluid into the PTU . Replace the input shaft seals, REFER to Input Shaft Seal .