grinding noise from rear

Noises from the rear axle when making tight turns almost always emanate from the limited slip differential. When turning the wheels have to move different distances (outside wheel travels further) which requires that the diff clutches allow some slip to occur by sliding over one another.

29,000 miles? Pretty odd to have issues at that mileage but perhaps the age -- 8 years now -- is coming into play.

Easiest place to start is to change the oil: 75W140 full synth and a bottle of friction modifier.

If this fails to get rid of the noise you might be looking at having to pull the diff and poke around. Like I said though, it's pretty unusual to be having diff issues on a car that's been hardly driven...

Ford TSB 06-04-04 LSD chatter

+1 on above.

There is a Ford TSB dealing with this issue. Check out:

http://www.stangnet.com/mustang-forums/805121-wheel-hop-when-i-reverse-cut-wheel.html

http://www.stangnet.com/images/stories/docs/sn95_TSBs/06-04-04.pdf

My 02 was doing this when I bought it (~55k miles). We started with changing the fluid, didn't help one bit. So I wouldn't waste my time with that.

It took replacing the LSD clutches to fix it, but mine had apparently been doing it so long that it had chipped the spider gears, requiring replacement.

Luckily, the car came with a 30 day warranty, so it didn't cost me a dime. It DID cost the dealer about $1k with their discounts.

Diagnosing rear-end noises

Suggestion. The mileage is so low that your problem may be binding of the LSD clutches. Try this. Go to an empty parking lot and drive in slow tight circles both forward/backward/left/right. The intent is to hyper exercise the LSD. Perhaps this can free it up and save an LSD overhaul.

Also, for the cost of new fluid vs the cost of an overhaul, IMO, it is worth changing the fluid if for no other reason than to inspect the inside of the diff. Might be possible to spot what is really wrong. Besides, it will rule out fluid level/condition as a possible source.

The fluid fill hole is above the weight. It is visible from the front of the diff and somewhat high.

It is possible to glean a lot of information from the particular sounds made by a rear-end. Understanding the dynamics occuring also helps narrow down the problem area. Please see the following from the Ford service CD. Note the detail associated with each noise.

Now onto the REAL world. IMO, most of the time, the fix is the same. That is a rear end rebuilding kit is installed. Reason? The kit is not that expensive (about $100) and there is just not a lot of labor to be saved installing a partial kit.

Exception. For the home mechanic, installing wheel bearings is very easy. So if a rear-end can be brought back online by installing new wheel bearings, go for it. HOWEVER, in my experience, if a car needs new wheel bearings, the half shafts roller surface is also damaged. Expect to need new half shafts as well.

Carrier bearings can also be installed by most home mechanics. The services of a professional press will be needed to press on/off the carrier bearings. Many machine shops will do this sort of bench work as well as some repair shops.

Pinion bearings are much more difficult. Research before attempting if this is your first time.

My driveway is my shop. I do everything on axle stands and do not own a lift. I have found it worth the effort when rebuilding a rear-end to remove the entire axle from the car. This affords much improved access.

Good luck.

>>From Ford Service CD.
Axle Noise
NOTE: Before disassembling the axle to diagnose and correct gear noise, eliminate the tires, exhaust, trim items, roof racks, axle shafts and wheel bearings as possible causes. Follow the diagnostic procedures in Section 100-04 .

The noises described as follows usually have specific causes that can be diagnosed by observation as the unit is disassembled. The initial clues are the type of noise heard during the road test.

Gear Howl and Whine
Howling or whining of the ring gear and pinion is due to an incorrect gear pattern, gear damage or incorrect bearing preload.

Bearing Whine
Bearing whine is a high-pitched sound similar to a whistle. It is usually caused by worn/damaged pinion bearings, which are operating at driveshaft speed. Bearing noise occurs at all driving speeds. This distinguishes it from gear whine which usually comes and goes as speed changes.

As noted, pinion bearings make a high-pitched, whistling noise, usually at all speeds. If however there is only one pinion bearing that is worn/damaged, the noise may vary in different driving phases. If pinion bearings are scored or damaged or there is a specific pinion bearing noise, new pinion bearings must be installed. A worn/damaged bearing will normally be obvious at disassembly. Examine the large end of the rollers for wear. If the pinion bearings original blend radius has worn to a sharp edge, a new pinion bearing must be installed.

NOTE: A low-pitched rumble normally associated with a worn/damaged wheel bearing can also be caused by tires.

A wheel bearing noise can be mistaken for a pinion bearing noise. Check the wheel bearing for a spalled cup, and spalled/damaged rollers. Check the wheel bearing for rotating smoothness and end play. Install a new wheel bearing if any of these concerns are detected.

If the wheel bearing is damaged, the roller surface on the axle shaft may also be damaged. Install a new axle shaft if any damage is detected.


Chuckle
Chuckle that occurs on the coast driving phase is usually caused by excessive clearance between the differential gear hub and the differential case bore.

Damage to a gear tooth on the coast side can cause a noise identical to a chuckle. A very small tooth nick or ridge on the edge of a tooth can cause the noise.

Clean the gear tooth nick or ridge with a small grinding wheel. If the damaged area is larger than 3.2 mm (1/8 inch), install a new gearset.

To check the ring gear and pinion, remove as much lubricant as possible from the gears with clean solvent. Wipe the gears dry or blow them dry with compressed air. Look for scored or damaged teeth. Also look for cracks or other damage.

If either gear is scored or damaged badly, install a new ring gear and pinion.

If metal has broken loose, the axle housing must be cleaned to remove particles that will cause damage. At this time, any other new parts in the axle housing must also be installed, if necessary.

Knock
Knock, which can occur on all driving phases, has several causes including damaged teeth or gearset.

In most cases, one of the following conditions will occur:

A gear tooth damaged on the drive side is a common cause of the knock. This can usually be corrected by grinding the damaged area.

NOTE: Measure the end play with a Dial Indicator with Bracketry and not by feel.

Knock is also caused by excessive end play in the axle shafts. Up to 0.762 mm (0.030 inch) is allowed in semi-float axles. The frequency of the knock will be less because the axle shaft speed is slower than the driveshaft.

Clunk
Clunk is a metallic noise heard when the automatic transmission is engaged in REVERSE or DRIVE. The noise may also occur when throttle is applied or released. It is caused by backlash somewhere in the driveline or loose suspension components; it is felt or heard in the axle. Refer to Total Backlash Check in this section.

Additionally, clunk may be heard upon initial drive-away. This occurs as engine torque shifts vehicle weight, forcing changes in driveline angles, preventing the driveshaft slip-yoke from sliding on the output shaft. To correct for this condition, lubricate the slip-yoke splines.