Squealing while driving.

Hey guys. I just bought a 2004 Tacoma TRD. Just recently it started a very high pitched squealing while driving but only when running flat. It doesn't do it on acceleration and less when decelerating. There is NO vibrations or grinding. while driving I hear it on my passenger side but my passengers here it on the driver side so that tells me it's in the center if the truck. I was thinking a carrier bearing. Someone told me it was a wheel bearing but it doesn't act like that. Any suggestions on what it could be?

 

Check your brake booster, mine squeals really high pitch around the master cylinder because there's a leak between the master cyl and the booster. Goes away on acceleration and deceleration. Easiest way to test is just pop the hood, and it shut if off while idling, then run over to the booster and listen. Mine is loud so it was easy to diagnose.

 

I recently had the same problem. It sounded like a belt slipping, but if I shifted in neutral and reved the engine the squeal didn't change pitch. I also noticed that it was worse when off the gas. After searching a bit, the two most common causes are the carrier bearing and the u-joints. I had never greased the drive train / u-joints so I did that. I followed this thread for locations Knock on wood. I haven't heard it again although I only greased them about a week ago. Of the six zerks on the drive line, the only one I had put grease in was the slip yoke. The rest might have been factory grease in there.

 

A high pitch squeal could be the wear sensors and your disc pads.

 

read my thread here and the following one 2 posts down for some detailed information on symptoms, diagnostics, and repair on a bad carrier bearing.

like 90% sure it's your drive line. either from the carrier or the u-joints. no vibrations indicates the u-joints are still good. grease them first since that's pretty cheap to do.

watch this movie to see what bad play in the bearing looks like. also, if your transmission mount is bad and the tranny is sitting lower than it's supposed to, you wont have much play in the carrier since the tranny is pulling the drive shaft down at the carrier. it will feel tight.

 

Are you carrying any livestock?