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Does it always happen around 3k RPM? *NM*


All Porsches welcome!

Expect the best, and accept no substitute.
2003 Boxster base, approx 59000 miles

Issue: Occasionally, when driving (over 40 or so) I get this sensation that seems to be emanating from the "back" like I am driving over rubble strips. Nothing too serious, just that subtle noise and "feeling." It goes away with time and, occasionally, seems to correspond with letting off the gas (similarly, occasionally, accelerating seems to eliminate the "feeling"winking smiley

Any ideas. Good news is always appreciative especially where the wife is beginning to question our purchase lol

EDIT: Oh, and if it matters, the rear tires are definitely in need of replacement



Edited 1 time(s). Last edit at 02/23/2012 03:39PM by mnchstrcityblues79. (view changes)
Quote
mnchstrcityblues79
2003 Boxster base, approx 59000 miles

Issue: Occasionally, when driving (over 40 or so) I get this sensation that seems to be emanating from the "back" like I am driving over rubble strips. Nothing too serious, just that subtle noise and "feeling." It goes away with time and, occasionally, seems to correspond with letting off the gas (similarly, occasionally, accelerating seems to eliminate the "feeling"winking smiley

Any ideas. Good news is always appreciative especially where the wife is beginning to question our purchase lol

EDIT: Oh, and if it matters, the rear tires are definitely in need of replacement

If your tires are unevenly worn - specially "feathered" it can give that rumble strip vibration. When you're accelerating, you're putting load on the rear tires that might make the vibration less severe. When you slow down, the weight shifts toward the front of the car, which could make the vibration seem more severe.
...also
Guenter in Ontario - Thursday, 23 February, 2012, at 4:24:38 pm
if your tires are feathered or unevenly worn. Make sure you get an alignment when you get the new tires.
Re: ...also
mnchstrcityblues79 - Thursday, 23 February, 2012, at 5:24:19 pm
Thanks for the input, guys. I am less apt to believe its a bearing issue because I haven't experienced the tell-tale "womp womp". I am no mechanic but if I had to use an analogy to describe the issue, imagine a dog preparing to sit on command. As the dog begins to "crouch" (decelerating) the rumble vibrations start. If the dog decides to lift its back end out of the crouch (acceleration) the rumble stops. It's almost like a "settling" occurs that is accompanied by the rumble. You feel it in the seat of your pants.

Does that make ANY sense? Lol

(PS: I am a dog owner, thus the weird analogy)
I just fixed a similar problem at the dealership..
Kimo - Thursday, 23 February, 2012, at 5:09:15 pm
it's a whomp...whomp...whomp noise that gets worse with speed. I originally thought it was my tires too, since I haven't balanced my wheels in a while and the odd winter temps played havoc on tire pressures. In the end, I read several boards and some boarders with the same issue said their wheel bearing was the issue, i.e. worn wheel bearings. Since my problem was obviously the driver's front tire area, I asked the dealership to have the mechanic take it for a fast test drive....and the mechanic said it was the bearing...yada yada yada...they replaced the wheel bearing and rides smooth and without the whomp whomp whomp or crazy vibrations.

If your situation doesn't vibrate your car much, and your wheel bearing is the fault, then you may have an early stage of worn out wheel bearings.

I'm not saying that's your problem, but that's what my issue turned out to be.

Best of luck to you...cost me $382 for wheel bearing replacement.
Trouble is my experience is that a bearing is bad is not often than clear. There is some noise -- noticable only after replacing 4 very worn and very noisy (Pirelli) tires -- but even then which bearing was the bad one was hard to determine. No play or other symptoms/signs, just a noise coming from the rear of the car.

Could be something as simple as a wheel lost a weight?

Another possible cause: I have been told is that in some cases the tires wear and they go out of balance. The techs tell me this is quite a problem with the Cayenne and its (large) tires but it happens with all models.

I note you did mention the rear tires are definitely in need of replacement. So it could be a weight was lost or the tires simply wore down enough to change the balance characteristics of the tires.

I assume tire pressures are good? I have found just a few pounds overinflated front tires will cause the car to vibrate like there's a tire balance problem. While you are not complaining about a tire vibration the vibration causes the tire noise -- which in my experience can rise to pretty high levels when the tires get near to the end of their life -- to vary which might be mistaken for a bad wheel bearing.

Sincerely,

MarcW.
Does it always happen around 3k RPM? *NM*
Boxsterra - Thursday, 23 February, 2012, at 8:41:13 pm
Good call on the 3K rpm check
dghii - Thursday, 23 February, 2012, at 8:58:03 pm
Also might want to peek under the rear of the car and look at your CV boots. I developed a vibration last summer when my boots tore. My vibration was most notable at freeway speeds.
Its worth a quick look for tears in the boot or grease flung about the bottom of your car.

dghii 2000 Boxster S 6speed 112k miles
Two very common issues are worn wheel bearings and bad motor mount. If your sound doesn't seem proportional to wheel rotation, I'd check the motor mount next.
My 97 has this same issue, but only when I get the RPMs around 5K, I really think it's motor mounts, and once it warms up I'm going to have it looked at. What RPM do you feel the rumble?

Damon
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