FYI

[WAM]

I'm posting this because it may be of some help to someone someday.

I have not owned this car long and from day one every time I back down my driveway and turn onto my street the car was making a crunching/rubbing noise from what seemed to be the right rear of the car and for a mile or so it seemed like a rattling noise that made me think the lug nuts might be loose. All of the noises would go away once it was run for a while.

I was under the car looking things over. The shocks were dry and wheels were tight.

The car only has about 9700 miles on it but it is 11 years old.

On a hunch I decided to have the rear oil changed thinking it was the cheapest thing to try before paying someone to try and figure it out.

I took it to the Cadillac dealer and had it changed. I told the tech why I was doing it and he told me the oil that came out looked clean which made me think I just wasted $100.

Took the car home and let it sit a day and then backed it down the drive onto the street and NO NOISE. Now I wasn't convinced but I let the car sit another two days and I tried it again and still no noise.

I really hate to say this but I think the oil change did the trick. The oil looked clean but maybe the friction modifier in the oil breaks down over time. There is a slim possibility that someone in the past changed the oil and replaced it with the wrong oil.

In any case I'm happy for an easy fix.

I sure hope this post is not going to jinx me.

 

[nerkpowers]

There is actually a TSB on this ( Technical Service Bulletin). Usually described as chatter while turning. I had mine changed this year for the 'chatter'. It almost sounds like the fluid was low enough that it took a 1/4 mile or so for the gears to get fully coated with the diff fluid. Fix for the following TSB was, I think, to either top off or change the differential fluid.

TSB No.: 3559NHTSA No.: 10016945TSB Date: January 1, 1901Date Added to File: October 18, 2005
Failing Component: Power Train Axle Assembly
Summary: Rear axle chatter shudder on turns. Updated

Tim


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[Phil105]

TSB

Had the same issue right after I got my car in August - 22,000 miles on it. Found the following on this forum and it was the fix and yes, it was put out in a TSB. Note the change in oil to be put in.

1. Important: DO NOT add any limited-slip additive (friction modifier). With this new fluid (Dexron LS Gear Oil 75W-90) it is no longer required to add friction modifier. If friction modifier is added, it will cause the fluid to lose some of it's friction reducing properties as well as reducing seal life.
   
   
   

   Fill the differential with the new DEXRON® LS gear oil, P/N 88862624 (Canadian P/N 88862625). Refer to the table listed below for lubrication specifications.Check the fluid level to ensure it is even with the bottom of the fill plug hole to no lower than 6 mm (0.25 in) below the opening.Install the fill plug and washer to the differential. Tighten
   Tighten the differential fill plug to 35 N·m (26 lb ft).
   Important: Steps 8-13 are for vehicles equipped with the differential cooling system. For vehicles not equipped with the cooling system, proceed to step 14.
   Raise the vehicle so the wheels are about a foot off the floor. Make sure the wheels can spin freely without obstruction from the hoist or any nearby items. Start the vehicle and put the transmission in second gear. Slowly accelerate to 10 mph and hold this speed for one minute.Turn the vehicle off . Raise the vehicle. Check the fluid level in the differential. Add fluid until the recommended level is reached. Lower the vehicle.
   ​
2. Once the differential fluid has been changed, the vehicle must be driven in 8-10 tight figure eight maneuvers to heat the fluid and allow the fluid to be worked into the clutch plates.

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