Lincoln Aviator 2020-2024 Service Manual / Chassis / Driveline / Front Drive Axle/Differential / Diagnosis and Testing - Front Drive Axle

Lincoln Aviator: Front Drive Axle/Differential / Diagnosis and Testing - Front Drive Axle

Principles of Operation

Inspection and Verification

Verify the customer concern.

Visually inspect for obvious signs of mechanical or electrical damage.

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

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

Symptom Chart - Front Differential

Condition	Possible Sources	Actions
Axle overheating	Axle lubricant low	CHECK the lubricant level. FILL the axle to specification. REFER to: Specifications (205-03 Front Drive Axle/Differential, Specifications).
	Incorrect or contaminated lubrication type	INSPECT the axle for damage. REPAIR as necessary. DRAIN and REFILL the axle to specification as necessary. REFER to: Specifications (205-03 Front Drive Axle/Differential, Specifications).
	Bearing preload adjusted too tight	If low mileage unit, CHECK the ring and pinion for damage. INSTALL new front axle as necessary REFER to: Axle Assembly (205-03 Front Drive Axle/Differential, Removal and Installation).
	Excessive gear wear	INSPECT all the axle gears for wear or damaged. INSTALL new front axle as necessary REFER to: Axle Assembly (205-03 Front Drive Axle/Differential, Removal and Installation).
Broken gear teeth on the ring gear or pinion	Insufficient lubrication	INSTALL a front axle assembly. REFER to: Axle Assembly (205-03 Front Drive Axle/Differential, Removal and Installation).
Differential side gears / pinion gears are scored	Incorrect or contaminated lubricant type	Drain and FILL the axle to specification. REFER to: Differential Draining and Filling (205-03 Front Drive Axle/Differential, General Procedures). Road test vehicle. If an observable symptom is present (noise from front axle), INSTALL new front axle assembly as necessary.REFER to: Axle Assembly (205-03 Front Drive Axle/Differential, Removal and Installation).
Lubricant leaking from the pinion seal, axle shaft oil seals	Vent	CLEAN the axle housing vent.
	Damage in the seal contact area or pinion flange dust shield	INSTALL a new pinion nut and the pinion seal if damage is found. REFER to: Drive Pinion Seal (205-03 Front Drive Axle/Differential, Removal and Installation).
	Damage in the seal contact area	INSTALL a new halfshaft seal as necessary. Inspect Halfshaft seal contact area. Install new halfshaft as necessary. REFER to: Axle Shaft Seal (205-03 Front Drive Axle/Differential, Removal and Installation).
Grease expelling from pinion splines	Missing / worn / damaged driveshaft to pinion circlip Missing / Damaged front axle pinion stem O-Ring	REMOVE the Front Driveshaft. INSTALL New Circlip and O-Ring. INSTALL the new Front Driveshaft as necessary. REFER to: Front Driveshaft (205-01 Driveshaft, Removal and Installation).

Symptom Chart - NVH

NOTE: NVH symptoms should be identified using the diagnostic tools that are available. For a list of these tools, an explanation of their uses and a glossary of common terms, refer to Section 100-04. Since it is possible any one of multiple systems may be the cause of a symptom, it may be necessary to use a process of elimination type of diagnostic approach to pinpoint the responsible system.

REFER to: Noise, Vibration and Harshness (NVH) (100-04 Noise, Vibration and Harshness, Diagnosis and Testing).

Symptom Chart - NVH

Condition	Possible Sources	Actions
NVH concern isolated to front axle using proper diagnostic tools. Symptom may be constant or only occurs under specific driving conditions	Axle lubricant low or contamination	CHECK the lubricant level. FILL the axle to specification. REFER to: Differential Fluid Level Check (205-03 Front Drive Axle/Differential, General Procedures). OR INSPECT front axle fluid, if required, Drain and FILL the axle to specification. REFER to: Differential Draining and Filling (205-03 Front Drive Axle/Differential, General Procedures).
	Internal FDU (Front Drive Unit) damage	Remove side cover and inspect components for wear or damage. INSTALL a new FDU (Front Drive Unit) as necessary. REFER to: Axle Assembly (205-03 Front Drive Axle/Differential, Removal and Installation).
Driveline clunk - loud clunk when shifting from REVERSE to DRIVE	Loose or missing fasteners	CHECK all driveline fasteners for proper torque.
Driveline clunk — occurs as the vehicle starts to move forward following a stop	Loose front axle mount	CHECK the front axle for loose bolts. TIGHTEN to proper torque. REFER to: Axle Assembly (205-03 Front Drive Axle/Differential, Removal and Installation).
Driveline clunk — occurs during acceleration or from cruise to coast / deceleration	Rear driveshaft U-joint Missing or damaged circlip on front axle pinion.	INSPECT the rear driveshaft U-joints for wear or damage. INSTALL a new rear driveshaft as necessary. REFER to: Rear Driveshaft (205-01 Driveshaft, Removal and Installation). Install new circlip.
Grunting — normally associated with a shudder experienced during acceleration from a complete stop	Rear Driveshaft	INSPECT the rear Driveshaft. INSTALL the new rear Driveshaft. REFER to: Rear Driveshaft (205-01 Driveshaft, Removal and Installation).
Scraping noise — a continuous low pitched noise starting at low speeds	Intermediate shaft LH halfshaft seal deflector bent / damaged	INSPECT components for wear/damage. INSTALL a new LH Halfshaft seal as necessary. REFER to: Axle Shaft Seal (205-03 Front Drive Axle/Differential, Removal and Installation).
Driveline shudder – occurs during acceleration from a slow speed or stop	Rear driveshaft	INSPECT the rear Driveshaft. INSTALL the new rear Driveshaft. REFER to: Rear Driveshaft (205-01 Driveshaft, Removal and Installation).

Axle Fluid Analysis

The appearance of milky fluid could be caused by fluid contamination. Drain and refill fluid and retest for normal operation.
REFER to: Differential Draining and Filling (205-03 Front Drive Axle/Differential, General Procedures).

Analysis of Leakage

Clean up the leaking area enough to identify the exact source.

Axle Vent

A plugged vent will cause excessive seal lip wear due to internal pressure buildup. If a leak occurs, check the vent. If the vent cannot be cleared, install a new vent.

Drive Pinion Seal

Leaks at the drive pinion seal originate from the following causes:

Damaged seal
Worn seal surface on Pinion Nut

The service kit available comes with seal, nut, & deflector.

Differential Seals

NOTICE: When installing shafts, do not allow splines to contact seals during installation or damage to the seals may occur.

The front axle fluid level is above halfshaft. Top-off the fluid level after replacing either differential seal. The seals are one time use and should be replaced whenever the RH halfshaft or intermediate shaft is removed.

RH halfshaft seal is a typical unitized seal found on many applications. The LH differential seal is the intermediate shaft to oil pan O-Ring.

The intermediate shaft also contains a differential seal to prevent gear lubricant from entering the intermediate shaft. This seal is serviced with the intermediate shaft.

Description and Operation - Front Drive Axle and Differential

The 6.5-inch ring gear rear differential axle has 3.31, 3.58 and 3.73 gear ratio versions. Front Drive Axle and Differential The front drive axle consists of: A cast-aluminum center section, a removable cast-aluminum differential housing cover Integral-type housing hypoid gear design (center of the pinion set below the centerline of the ring gear)...

General Procedures - Differential Draining and Filling

Materials Name Specification Motorcraft® SAE 75W-140 Synthetic Rear Axle LubricantXY-75W140-QL WSL-M2C192-A Draining With the vehicle in NEUTRAL, position it on a hoist...

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Child Safety Locks

When the child safety locks are set, you cannot open the rear doors from the inside.

Lincoln Aviator. Child Safety Locks

The child safety lock control is on the driver door.

Press the control to switch the child safety locks on. Press the control again to switch them off. A light on the child safety control illuminates when you switch them on.