Deep humming noise from under TB While driving?

[kchristensen]

I have a 07 Trailblazer that I just bought a few months ago and about a week ago I started to notice a humming noise coming from under the TB while i'm driving. It almost sounds like if I had mud tires on but I don't. It changes pitch as I accelerate and decelerate. Does anybody know what could be causing this noise?

[The Roadie]

Welcome! How many miles does it have, and did you immediately change all the fluids if you didn't get a maintenance history? The transfer case fluid is a surprisingly low 50K miles. Other fluids 100K. Other maintenance also due at 100K - check the Owner's Manual.

Your noise may be the transfer case or something else in the drivetrain. Or a wheel hub/bearing assembly. The front bearings have a relatively short lifetime, and often (but not always) change their sound if you turn left or right and change the stress on one side or the other. Does your 4HI function work, and does the noise change if you engage it for a short time while going straight ahead in a parking lot?

[kchristensen]

I'm at 117,000 miles. I had the oil changed immediately. But have have not got to the other fluids yet. The sound I hear does not seem to change while turning, it only changes pitch while accelerating or decelerating the 4hi does work. I will have to take it for a drive to see if the sound changes with it engaged.

[Mooseknuckle]

welcome! Roadie said it best. A lot of good knowledgeable people on this site. Good luck

[kchristensen]

Ok so noise does not change whether its in 2wd or 4wd. Checked both engine oil and trans oil both levels are good. I looked under and noticed that I do have a leak of some sort from somewhere in the front but haven't got under to figure out what or where yet. Once I get the noise issue solved and fixed I plan on changing out all the fluids so what is recommended?

[The Roadie]

... I plan on changing out all the fluids so what is recommended?

Checking the Owner's Manual for the recommended fluids and amounts, then firing up a Google session to see how it's done would be my recommendation. If not here, then our sister site GMTNation.com shold have a lot of discussion about simple maintenance and fluid changes.

[Jimbo121]

I'm going to say if it sounds like it is up in front, have the front hubs checked????

[navigator]

a little more info on checking the wheel bearings, head down the highway at like 50 or so(when you hear the noise best) in a straight line and like bump the steering wheel slightly from like 12 oclock to 1 and then from 12 to 11. If the noise gets quieter it is likely a wheel bearing. If it gets quieter when bumping right it is the left bearing and if it gets quieter when bumping left it is the right bearing. I just bought a pair on ebay for $76. I've only had them a few week so I can't give a real review yet.
I tried every test in the book and this was the only way to tell. I even pulled one off and checked it and rolled it and I really couldn't tell anything was wrong other than it felt like maybe the grease was a little thick. No play or anything in it.

[Flying Monkey]

After changing my clunking cv on drivers side there was still a humming sound from the passenger side. I changed my other CV and its gone.....other then my tire noise lol

[DirtyBacon04]

peh, the proper solution for the humming noise is to turn up the music. Just drive it till it breaks so you know for sure whats wrong.............................

[SaltWaterDrinker]

When I had that humming noise it was my wheel hub bearings.

The next instance that produced a weird noise was the lower ball joints.

If it is at all coming from the front of the truck, that may be what it is...per my experience with it, of course.

[kchristensen]

Thanks for everyone's help! I got the prob all figured out! Thanks "navigator" I did your straight line test with the turns and it turned out to be the Ft. Driver side hub. changed it out yesterday and everything is good now!

[DirtyBacon04]

Glad you got it all figured out!

[navigator]

glad we could help, I just recently had the same problem and picked up the troubleshooting tips from here as well.

[Conner299]

So, I have done my searching with the search bar. I have read through most of the threads on this subject, which I now seem to be experiencing myself. I haven't had a chance to do the "Veer-Test". I, at first, thought it was road noise from new tires. This seems to be more pronounced, and deeper in sound, than the sound I get from the tires when I first got them. It is mainly heard at average highway speeds, and gets louder going around turns, either left or right. My main question is this: Can you buy just a rebuild kit(bearing, races, and seals), and if so, is this advisable? I have looked around and found complete hubs, and bearings & races under the same category as the hubs. Everything I read talks about just changing out the complete hubs. Guidance appreciated...

[v7guy]

The trailblazer has a sealed hub with an ABS sensor and they can't be rebuilt. You can only replace it. The cheap no name hubs are known to have a high failure rate and I've read several threads where they only lasted a year. Many people pony up for the Timkens and have many years of trouble free service (unless you have 35s and go offroad frequently).
Lots of info here and on GMTnation.