2004 DeVille noise coming from driver's rear wheel area

[GMC]

This has been a tough one.  I have a 2004 Cadillac DeVille with 50,000 miles - always serviced and maintained.  Occasionally I hear a series of claps/taps coming from the rear wheel area.  On a different forum, I found this person who was having exactly the same problem. He said,

"I have kind of a weird question just sitting in my car with it on I hear a knock knock knock knock knock coming from the driver side rear wheel area any idea what this could be I have no codes and the car is driving and acting perfectly fine it's not a very loud noise but it just sounds like somebody is tapping somewhere by the driver side rear tire area. Usually it's about four or five taps all within two or three seconds."

I couldn't describe what I'm hearing any better than this; however, the sounds are seemingly occurring randomly, and I did get a clue today.  As I pulled into my driveway, the normally quick sequence of taps happened to start, but as I was almost stopped, the noise slowed with my decrease in speed.  This tells me its likely involving some part within the wheel well ie ABS, emergency brake, load-leveling system, etc.  I do have a short loud brake squeak coming from the same wheel when I back out of the driveway, but it always stops when I drive forward - (the pads still have good life).

I'm hoping someone has heard of this weird noise sequence - I've seen several forums that have discussed this problem, but no conclusion on what the problem was found to be.  Any theories out there?

GMAC

 

[Logan]

My first guess is maybe the exhaust system? The pipe will grow over a inch between being cold and hot. 

Some cars.....after you turn it off. If you sit in the car for a minute.....you may hear it shrinking.....donk....donk...donkdonk kind of thing.

[GMC]

Thanks for your response.  The noise seems to be connected somehow to the wheels turning.  After researching, their seems to be several possible culprits.  The wheel hub assembly is suspicious, as is the auto load leveling system.  Some think it could be a faulty solenoid.  Who knows?  Again, thanks for the response!