[josephmartins]

2000 Avalon XLS, 93k miles. This began recently and only occurs over 70-72mph. It's consistently repeatable.

Once we reach that speed it sounds briefly like fingernails on a chalkboard, intermittently, and disappears below 70mph. A/C on or off, does not matter. Slight bumps/uneven surfaces don't affect it. Doesn't seem like the belt. Haven't had the guts to push it harder to see if it occurs at higher speeds. Any suggestions?

 

[josephmartins]

[UPDATE]

I discovered that this had to do with the metal "skid plate" beneath the front fascia. I had removed it to install the new radiator this summer and had not reinstalled it. Several bolt heads had snapped during removal due to rust. I have to cut the nuts off and tack weld new ones on to reinstall the plate. For now we're driving without it.

Two plastic panels beneath the Avalon attach to the plate with a couple bolts. With the plate removed the plastic panels are not attached rigidly along one edge. My best guess is that the plastic panels begin vibrating above certain highway speeds...much the same as a piece of paper vibrates as you blow air over its surface.

If my hunch is correct, this particular noise should disappear once the plate is reinstalled. Of course, now I have a new noise to deal with (a loud buzz) and I'll make that the subject of another thread.

 

[TedL]

With squeal present, turn O/D off. RPMs should jump. Report what happens to the squeal.

 

[josephmartins]

Way way off...

I know this is an older thread but I want to make sure others are aware of the solution.

It wasn't the plate underneath the car. It was....are you ready for this...the fuel door. 18 months after racking my brain over this and not finding a solution I accidentally figured it out.

I removed the fuel door to replace it recently. No more noise at any speed. I am guessing that as the fuel door hinge began to fail and the door would no longer close tightly, it vibrated against the body as air flowed over it. That's the high pitch vibration we heard at highway speeds.

So now you know.