Bought my 05 CTS used and on the drive home noticed a strange rumbling/wobbling noise coming from the front driver side. Took it to my buddies garage, he attempted to re-balance the wheel only to find out that the wheel was bent. Ordered new wheels, just had them put on, they balanced out perfectly, but of course that doesn't fix the problem and I still have this noise. It happens most frequently around 40mph, happens any time there is a variation in the road surface (bumps) and seems to increase with turns. The best way I can think to describe it is it sounds like the wheel isn't tightened all the way down (it is by the way) and it's wobbling on the studs. That's what it SOUNDS like, but not what it is. Any idea on what is causing this noise?!? Doesn't seem to be too serious considering everything is still functional, but it's obviously a noise that it shouldn't be making so I want to get it corrected. Any suggestions?!?!? Thanks for any info you can provide!

How many miles on the tires? On the CTS you have to rotate the tires every 6k or they will CUP. Run you hand alond the edges of the tires to see if there is any cupping on the tire. I had to discard some tires with 20k miles on them because the noise was driving me nuts, now I'm religous about rotating and them.

One other problem I had when hitting small bumps with the CTS is that the Stabilazer bar bushings were worn. If you remove the tire and look at the rubber block that holds the stabilizer bar, it should be tight and there should be no gaps. Mine were loose and worn, I took a bunch of zip ties (big ones) and put them throught there and it tightened it up and now the noise is gone.

If the wheel is bent id suspect it was in accident or hit something rather hard...

There could be another cause but consider this.
I have seen a few that have a rattling type noise that comes from the brake caliper area.

The caliper is held in by two bolts that screw into two pins that slip into the caliper mounting bracket.
The clearance inside the bracket can be weird and if not properly lubricated the pins will rattle on a washboard type surface or bumpy road as the caliper bounces up and down from the force.

To fix THIS problem just remove one caliper bolt (the bottom one) and swing the caliper up then slide it inboard to remove the upper pin, the bottom pin will just slide out.
Get some good brake hardware lubricant that will stand up to the high pressures and apply it to the pins and the bores, remember not to overdo it but don't be too shy.
Slide the lower pin back in, put the upper pin back in by sliding the caliper back into place and and make sure the boots are seated in the groove. Reinstall the lower caliper bolt, wipe off any excess grease that came out and put the wheels back on, torque the lug nuts properly. Road test it and see if the noise is gone.

the symptoms u decribed lead me to believe its a worn or cracked wheel hub/bearing. i had one of these go bad with mine except it was my passenger side rear wheel. same thing... the whoop whoop whoop sound and even louder whoop whoop wen cornering. whenever i would hit a dip in the road with that wheel it would cause my back end to wobble slightly for a quick sec as well. hope this helps...

I will second that it sounds like a wheel hub bearing.

yup thats the wheel hub baaring.. i just replaced that today...

hmmm...well my warranty covers that so I'll be scheduling an appointment soon. Last place I took it to said it was the bent wheel, think I'll be trying a Caddy dealership this time.

having a similar issue with my right rear. how much to repair/replace for you all? do work yourself, or dealership?

nevermind... search! :D