BrilliantBob

Completely stock. As you know, they're very quiet! Perhaps if I go aftermarket I won't be able to hear the droning...

Slakker

And it's speed related not RPM related?

I would get an alignment and another balance just to eliminate that from the equation.

With the windows down, the sound should get better or worse when turning if it's a wheel bearing.

Next up is the axle. You can get a salvage one for $100 and the swap out is a couple of hours DIY (so plan a day of you're not familiar with these). Read through the pelican how to prior to make sure you have the tools on hand.

BrilliantBob

It does get louder with speed, but it's not a rotational sound that gets faster as the speed rises.

I haven't noticed any change in the noise when turning right or left. I do think that the vibration might get slightly worse when the 'wheel is turned though.

skiracer

I brought my car in to change the motor mounts, and they found a transmission mount that was shot and in need of replacement. My clunking and droning went away completely after a new mount. Maybe check this out as well?

5CHN3LL

For clarification: You will not be trying to troubleshoot this on your own?

Might as well quit soliciting suggestions, then - unless you really want to sour the relationship with whomever the car winds up with, in which case be sure to hand him a printout of this thread when you hand over the car.

For maximum impact, use the following wording:
"I know you're supposed to be pretty good, but I got some expert advice off the Internet."

You really need to emphasize "expert" - you can't hit that word too hard. It's key; do it wrong, and he's merely annoyed; do it just right, and he'll go berserk.

Niceguyeddie

You have vibration and noise: I simply HATE taking my car into the shop for stuff like this...they always misdiagnose or write up 5 other things that might be wrong instead of the primary cause. My advice is to jack it up or put it on a rack and figure out what is worn out. There should be no play and usually your eyes can spot something that is loose/worn. I spent perhaps $500 on my front end and over 10 hours replacing parts. I still have to replace the struts and tires but it is 95% better than it was.

I'm thinking you should have those tires' balance re-checked and also a 4 wheel alignment is in order. If there is a slight jarring that is enough to cause some "curbage" or scarring of the inside of the rim, it could have knocked that wheel out pf alignment. The only way you can tell for sure if alignment is out, is uneven tire wear. Since you have new tires...the evidence was thrown away with the old tires.

Larry Hughes

I had a very similar set of problems on my 139,000 mile 2001 996: clunking and drone.
Tires make a HUGE difference. I replaced Pirellis with Michelin PS2s and it was a great improvement. I could barely stand to be in the car with the Pirellis.
Clunking proved to be sway bar end links. I replaced end links and bushings for about $110 for the front and same for the rear. Big improvement. Clunks are gone.
I still have some droning. Speed related, not RPM. Toeing the brake doesn't seem to change the drone. I don't think it can be the tranny mount as the drone is the same with clutch disengaged. I suspect wheel bearing and/or CV joint. Will work on that.