I hear a metal on metal scraping/screeching sound with the windows down and only when i drive by guard rails and other stuff sound reflects off of. I saw the traveling hub zerk thread and that's what made me think of it. I've zerked every fitting I've seen, but this ones new to me. Problem is I can't even tell witch wheel (if any) it's coming from. It's consistent with speed.

 

It could be a small rock stuck somewhere.

 

I see you have a thread about warped rotors... do you have a stuck caliper?

 

To add to the confusion, I've has it jacked up before and manually spun the wheels and not heard the sound. It was by hand, so maybe it wasn't fast enough. I can get them going pretty fast with my pressure washer. Maybe I should try that?

 

Jack it up and shake the wheels to check for bad front bearings, try it in 4wd, and check your ujoints.

 

I recently had the exact same noise in one of my cars, it was a broken brake caliper.

 

Going off of what EXv10 said, there shouldn't be any play in the wheel whatsoever. You will notice wheel bearing play most when you are moving the camber of the wheel (this is the best way I know how to say it in text)

 

mispost,,,

 

Shake the wheel at the top.

 

I've heard that sound twice before. The first time, it was a missing caliper bolt. The second time, it was a bad front hub.

 

Take it all apart and inspect.
Strap a tape recorder all around.

 

I have a metal to metal sound that happens at about 2300 rpm and goes away at 2700 rpm and will do the same coming down on rpms. I think it is the torque converter rubbing up against a dust shield. I've never looked into it and it's not getting worse. One of these days I may look.

 

Not sure if this is it or not, but I had a similar noise. It turned out to be one of the front hubs. The outer o-ring on the turn **** was working its way out of the hub. Try putting it in 4wd high(while driving straight) if it goes away it's the same issue I had. Took hub apart and cleaned and regreased everything. No more noise. It was the gear that had 2 rows of teeth that locks the axle to the hub they were rubbing ever so slightly.