strange noise - need help diagnosing
Several weeks ago I noticed what sounded like a tire noise on my '92 SSE */c so I took the car in and got 2 new tires to replace the 2 that needed replacing anyway. Now I have 2 brand new tires and 2 almost new tires, all of which are Kelly Navigator Platinums, P225/60R16, but unfortunately the noise is still there. It'* hard to hear, but can most easily be heard from roughly 20-45 MPH, but only with the windows closed because the noise isn't loud enough to hear when there'* outside traffic or road noise.
The noise is kinda like a hhh-hhh-hhh noise that varies in frequency (but not intensity) with speed, and doesn't change around turns or when braking. The noise occurs when coasting in neutral too. There'* no squeaking, humming, clunking, thumping, vibration, shuddering, or any other symptoms while driving, turning, or braking, and I can't feel any vibration.
Since the noise sounds like it'* coming from the rear, I took the car in again and asked them to put the rear tires on the front. I took it for a test drive, but to my surprise the noise still sounds like it'* coming from the rear, so although the 2 slightly older front tires seem to have a little scalloping on the outer treads, this can't logically be the cause of the rear noise, right? The slightly scalloped tires are now on the front, and the noise still sounds like it'* coming from the rear.
So I asked them to check the rear drums, the rear bearings, and the front CV boots and joints. They said everything was ok except the struts and shocks, so I had them replace the front struts with KYB GR2s and replaced the rear air shocks with Monroe air shocks. They said the noise I reported is 'probably' gone but there'* a little bit of tire noise and the 2 front tires should be replaced. I wasn't about to spend another $250 to replace 2 tires that only have a few thousand miles on them, so I paid the bill and left.
I drove the car home, and guess what? That noise is STILL THERE! I knew this was going to happen, and I've spent several hundred dollars and it didn't change anything!
Do any of you experts have any ideas?
'99 Bonneville SLE, white, 112,000 miles
'02 Park Avenue Ultra, white diamond pearl, 88,000 miles