[Rey]

Wrote the other day that I haven't experienced rear end problems, but today I am not so sure.
When the car is cold or even after being parked for an hour, backing up and cranking the steering tight I am hearing a low frequency "thump, thump, thump". At first it sounded a bit like a heavy bass radio response. Now the sound is a bit more mechanical. It is definitely tied to the rotational speed of rear wheels. My sense is that it may be related somehow to the limited-slip components of the rear end. But, I do not know anything about rear ends.
This sound arises only when the steering wheel is max crank at slow forward or reverse speed. There is no such sound, at this time, while turning 90 degree residential corners or otherwise.
I am wondering if this is the sign of an eminent failure. Of course this always happens on the eve of a long trip. Thanks for your comments.

 

[Flyboy]

I've been told it's the clutches within the diff....and regrettably, it's probably on it's way out.......safe to drive IMO. (Mine does that too).....waiting for the new P/N later in the year.

 

[gswoff]

Same EXACT problem here, low grinding noise at low speed turns... very easy to hear. Diff fluid swapped at 4k, now at 7k... on original diff.

 

[vonhiner]

My first rear end went out about 5500 miles with the whining problem starting about 40mph. A new diff was installed which lasted about 300 mi. with the same symptems yours has. (grinding noise when backing out of or into parking space) They ended up putting in a second diff and said the clutch pack went out. It did seem to be ok going down the road...don't know if it is ok for your trip or not. Chris

 

[crowan]

I just stopped by Lindsay Cadillac yesterday to discuss the same problem. I'm going to have it looked at next week when I take the car in for regular service. I'll post results when I get them.

The sound is awful, but at speed, I do not have any gear whine or other noise from the diff. Go figure.

CR

 

[Lindsay Cadillac]

Rey

From your description I'd say something is going on in the diff... It may not be a "failure" though... It could be something as simple as the fluid needs to be changed out... Would really need to hear it to say for sure...

James

 

[ahahnu]

I just had a diff repair last week. I herd something like that, not quite a thump, but now in whines real bad at 40 and above in 4th. Whined in sixth, which it didn't do before the repair.

 

[a64pilot]

I've been told it's the clutches within the diff....and regrettably, it's probably on it's way out.......safe to drive IMO. (Mine does that too).....waiting for the new P/N later in the year.

Yes should be the clutches. Yes it's safe to go on the trip if it's the clutches. Put the additive in. Takes two bottles for an Fbody, don't know about ours but I bet it's the same. If it's the clutches it should quiten it right up almost immedately and you can go on about life.

 

[cts-v ls6]

My '04 V was making the same noise when backing out of the garage every morning. Phil at DTE advised me to try Red Line lube AND the GM additive [1 bottle]. I did this changeout and the noise stopped immediately. I had no metal particles in my oil at all. But, the diff whines loudly, especially at 45 mph. I have 34k+ miles.