Driveshaft RPM and odd rubbing noise: trying to figure this out.

[Montego Murph]

Ok. I'm away from home and trying to figure something out.

While driving over 30mph, I hear a noise like Im dragging a plastic garbage can. It started suddenly, but is getting more pronounced. We noticed it while driving 65, i pulled over but saw nothing.

Its a scraping noise, but seems to flutter sometimes. (Imagine dragging a tree branch out the car window and as it bounces on the road, it goes quiet briefly, then comes back.) Randomly, no rhythm. The noise is always the same, does not change pitch when car speed changes.

Not related to engine rpm, braking, or side of the car. Did the swerve/lean test to rule out wheel bearings.

I crawled under the car thinking it was a plastic bag or something. Nothing down there but car parts. Shields on the rear brakes seems secure, neither wheel seems hotter than the other

Sometimes after a stop it takes a while for the noise to start up, but most of the time it starts at 30 miles an hour like clockwork

No check engine, drag, metallic feeling, or lack of power.

So, Im wondering. Approximately what RPM does the driveshaft turn in relation to the wheels? My only guess is that a heat sheild came loose and at speed, the wind catches it and it rubs on the driveshaft, then makes the noise. But then I second guess myself becuase metal on metal at driveshaft RPM would sound like a grinding wheel. Plus now that I think about it, I did not see clean stripes scratched into the drive shaft where metal would have been rubbing on it.

Any ideas what I should check before I can get home into my own driveway and jack it up? I'm not allowed to do any maintenance where I am because HOA and lack of tools.

Hmmmm

 

[Ralphman]

Your drive shaft spins 3.73 times faster then your wheels as long as you have stock gears

 

[Rishi3]

Quick question, is it normal for my v6 5 speed 2007 sport to cruise 80 mph at 2200 rpm?

 

[CXS]

Ok. I'm away from home and trying to figure something out.

While driving over 30mph, I hear a noise like Im dragging a plastic garbage can. It started suddenly, but is getting more pronounced. We noticed it while driving 65, i pulled over but saw nothing.

I had something like that once, turned out the be a loose wheel well liner that would fold back and hit the tire making terrible noise. When going slow it would go back in place, go over 30-40 and it would fold back again hitting the tire.

 

[Montego Murph]

Epilogue

Well, I called it in my guess. Turns out the heat shield directly over the muffler had broken loose and was somehow (likely the wind) blowing against the driveshaft causing the noise. Eventually it settled into a position where it rubbed even at slow speeds, and there was a difference in pitch which helped us know where to look.

A few 10mm socket wrenches and fender washers got us back on the road again!

Hoping this works as a good reference for someone else searching for a similar issue later on down the line.

Murph