What on earth is this noise?

Hello all,

My 2001 TRD 4x4 is making a couple of really weird noises. It all started yesterday when I was on the freeway and I heard what sounded like maybe a bearing that is about to seize making a really faint noise. It almost sounded like the air rushing by the window rubber when the rubber gets old and doesn’t seal quite as well but that isn’t what it was. It sounded as though the noise was coming from either underneath or behind the cab of the truck. The noise seemed to mellow out by the time I made it home so I put off crawling under the truck until later.

This morning I started the truck up and heard a really loud noise that sounded like the squeal of a bearing that’s going bad in an idler pulley. This particular noise was coming from the engine compartment. I took off and drove around a bit and the sound stopped after about 5-10 minutes. I stopped and popped the hood and didn’t see or hear anything wrong at that point. I figured all was well again so I hopped on the freeway and headed to work. While on the freeway, the noise from yesterday reappeared and sounded as though it was coming from behind or underneath the cab of the truck again. About halfway to work, that noise also stopped. Once I made it to work, I crawled underneath and took a look. Both driveshafts are still securely mounted and none of the bolts that hold them in place are loose. I didn’t see anything else that looked out of place either.

I had the truck at Claremont Toyota just over two weeks ago for a 60,000 mile service so I’m wondering what they may have done to perhaps cause these noises. A few days after I had it serviced, I started to smell burning grease and saw that they had over lubricated the U-joints (which splattered all over the exhaust). I still smell burning grease and It has been over two weeks since I had my truck serviced.

Any idea what may be going on?