Symptom Chart - Noise, Vibration and Harshness (NVH)

WARNING: This page is about a different car, the 2009 Mercury Grand Marquis and 2009 Ford Crown Victoria. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Noise, vibration and harshness (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 NOISE, VIBRATION & HARSHNESS article. 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. If this is not the causal system for the symptom, refer back to NOISE, VIBRATION & HARSHNESS article for the next likely system and continue diagnosis.

Condition	Possible Sources	Action
Axle howling or whine	Axle lubricant low	CHECK the lubricant level. FILL the axle to specification.
	Axle housing damage	INSPECT the axle housing for damage. REPAIR or INSTALL a new axle as necessary. REFER to REAR DRIVE AXLE/DIFFERENTIAL - FORD 8.8-INCH RING GEAR article.
	Damaged or worn axle shaft bearings	CHECK for abnormal axle shaft bearing play or roughness. REFER to REAR DRIVE AXLE/DIFFERENTIAL - FORD 8.8-INCH RING GEAR article.
	Damaged or worn differential ring and pinion	INSPECT and INSTALL a new differential ring and pinion as necessary. REFER to REAR DRIVE AXLE/DIFFERENTIAL - FORD 8.8-INCH RING GEAR article.
	Damaged or worn differential side or pinion bearings	INSPECT and INSTALL new differential side or pinion bearings as necessary. REFER to REAR DRIVE AXLE/DIFFERENTIAL - FORD 8.8-INCH RING GEAR article.
Driveline clunk - loud clunk when shifting from reverse to drive	Incorrect axle lubricant level	CHECK the lubricant level. FILL the axle to specification.
	Excessive backlash in the axle	CHECK the axle backlash. REPAIR as necessary. REFER to REAR DRIVE AXLE/DIFFERENTIAL - FORD 8.8-INCH RING GEAR article.
	Damaged or worn pinion bearings	REPAIR or INSTALL new pinion bearings as necessary. REFER to REAR DRIVE AXLE/DIFFERENTIAL - FORD 8.8-INCH RING GEAR article.
	Damaged or worn U-joints	INSPECT the U-joints for wear or damage. INSTALL new U-joints or driveshaft as necessary. REFER to DRIVESHAFT article.
Driveline clunk - occurs as the vehicle starts to move forward following a stop	Worn driveshaft U-joints with excessive play	INSPECT the U-joints for a worn condition. INSTALL a new driveshaft or U-joints as necessary. REFER to DRIVESHAFT article.
	Loose rear axle mount	CHECK the axle for loose bolts. TIGHTEN to specification. REFER to REAR DRIVE AXLE/DIFFERENTIAL - FORD 8.8-INCH RING GEAR article.
High pitched chattering - noise from the axle when the vehicle is turning	Incorrect or contaminated lubricant	CHECK the vehicle by driving in tight circles (5 clockwise, 5 counterclockwise). FLUSH and REFILL with the specified rear axle lubricant and friction modifier as necessary.
	Damaged or worn differential (differential side gears and pinion gears)	REPAIR or INSTALL new differential side gears or pinion gears as necessary. REFER to REAR DRIVE AXLE/DIFFERENTIAL - FORD 8.8-INCH RING GEAR article for the rear axle.
Buzz - buzzing noise is the same at cruise or coast/deceleration	Incorrect driveline angles	CHECK for correct driveline angles. REPAIR as necessary. REFER to Driveline Angle Measurement .
Rumble or boom - noise occurs at coast/deceleration, usually driveshaft speed-related and noticeable over a wide range of speeds	Driveshaft is out-of-balance	CHECK the driveshaft for damage, missing balance weights or undercoating. REFER to Driveshaft Runout and Balancing .
	U-joints are binding or seized	ROTATE the driveshaft and CHECK for rough operation or seized U-joints. INSTALL new U-joints or driveshaft as necessary. REFER to DRIVESHAFT article.
Grunting - normally associated with a shudder experienced during acceleration from a complete stop	Loose rear axle mount bolts or suspension fasteners	INSPECT the rear suspension and axle. TIGHTEN the fasteners to specification. REFER to REAR DRIVE AXLE/DIFFERENTIAL - FORD 8.8-INCH RING GEAR article.
Howl - can occur at various speeds and driving conditions. Affected by acceleration and deceleration	Incorrect ring and pinion contact, incorrect bearing preload or gear damage	INSPECT and REPAIR as necessary. REFER to REAR DRIVE AXLE/DIFFERENTIAL - FORD 8.8-INCH RING GEAR article.
Chuckle - heard at coast/deceleration. Also described as a knock	Incorrect ring and pinion contact or damaged teeth on the coast side of the ring and pinion	INSPECT and REPAIR as necessary. REFER to REAR DRIVE AXLE/DIFFERENTIAL - FORD 8.8-INCH RING GEAR article.
Knock - noise occurs at various speeds. Not affected by acceleration or deceleration	Gear tooth damage to the drive side of the ring and pinion	REPLACE the ring and pinion. REFER to REAR DRIVE AXLE/DIFFERENTIAL - FORD 8.8-INCH RING GEAR article.
Scraping noise - a continuous low pitched noise starting at low speeds	Worn or damaged pinion bearings	INSPECT and REPAIR or INSTALL new pinion bearings. REFER to REAR DRIVE AXLE/DIFFERENTIAL - FORD 8.8-INCH RING GEAR article.
Driveline shudder - occurs during acceleration from a slow speed or stop	Rear drive axle assembly mispositioned	CHECK the axle mounts and the rear suspension for damage or wear. REPAIR as necessary. REFER to REAR DRIVE AXLE/DIFFERENTIAL - FORD 8.8-INCH RING GEAR article.
	Loose rear axle bolts	CHECK the rear axle for loose bolts. TIGHTEN the bolts to specification. REFER to REAR DRIVE AXLE/DIFFERENTIAL - FORD 8.8-INCH RING GEAR article.
	Driveline angles out of specification	CHECK for correct driveline angles. REFER to Driveline Angle Measurement .
	U-joints binding or seized	ROTATE the driveshaft and CHECK for rough operation or seized U-joints. INSTALL new U-joints or driveshaft as necessary. REFER to DRIVESHAFT article.
Driveline vibration - occurs at cruising speeds	Worn U-joints	CHECK for wear or incorrect seating. INSTALL new U-joints or driveshaft as necessary. REFER to DRIVESHAFT article.
	Loose axle pinion flange bolts	INSPECT the axle pinion flange. TIGHTEN the pinion flange bolts to specification. REFER to DRIVESHAFT article.
	Excessive axle pinion flange runout	CARRY OUT a runout check. REPAIR as necessary. REFER to REAR DRIVE AXLE/DIFFERENTIAL - FORD 8.8-INCH RING GEAR article.
	Driveshaft is out-of-balance	CHECK the driveshaft for damage, missing balance weights or undercoating. CHECK the driveshaft balance. CARRY OUT a driveline vibration test. REFER to Driveshaft Runout and Balancing .
	Excessive driveshaft runout	CARRY OUT a runout check. REFER to Driveshaft Runout and Balancing .
	Driveline angles out of specification	CHECK for correct driveline angles. REPAIR as necessary. REFER to Driveline Angle Measurement .

Analysis of Leakage

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

Inspect leaking area for any worn or damaged parts.

A plugged rear drive unit (RDU) housing vent can cause excessive pinion seal lip wear due to internal pressure buildup.

Verify the RDU lubricant level is at least 3-5 mm (1/8-3/16 in) below the bottom of the fill hole.

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 journal surface

Any damage to the seal bore (dings, dents, gouges or other imperfections) distorts the seal casing and allows leakage past the outer edge of the drive pinion seal.

The drive pinion seal can be torn, cut or gouged if it is not installed correctly. The spring that holds the drive pinion seal against the pinion flange may be knocked out and allow fluid to pass the lip.

Metal chips trapped at the sealing lip can cause oil leaks. These can cause a wear groove on the drive pinion flange and result in pinion seal wear.

When a seal leak occurs, install a new drive pinion seal and check the vent to make sure it is clean and free of foreign material.

A new drive pinion flange must be installed if any of these conditions exist.

Drive Pinion Nut

CAUTION: Install the drive pinion nut to the correct torque specifications or damage to the differential components may occur.

On some high-mileage vehicles, oil may leak through the threads of the drive pinion nut. This condition can be corrected by installing a new nut and applying threadlock and sealer on the threads and nut face.

Differential Seals

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

Halfshaft pilot bearing housing seals are susceptible to the same types of damage as drive pinion seals if incorrectly installed. The seal bore must be clean and the lip handled carefully to avoid cutting or tearing it. The seal journal surface must be free of nicks, gouges and rough surface texture.

For information on differential seals, refer to REAR DRIVE AXLE/DIFFERENTIAL - FORD 8.8-INCH RING GEAR article.