Possible bearing or rear diff problem

[BrianF]

So I am trying to track down a "humming" sound in my 06 TB. It starts around 40km/h and gets progressively louder up to highway speed. I feel a slight vibration in the steering wheel, which is similar to the sound being produced. I try to load the outside bearings by turning sharp but the sound is unchanged. of course I do not have a large smooth parking lot to pick up speed and maintain the turn. I had the Tb on blocks and individually rotated each front and rear wheel. I only felt a slight vibration on the front driver side strut as I did this.

Now the rears were smooth in rotation but had a slight amount of end play on each axle. You could move the wheel out a fraction of a millimeter, just enough to make a sound. Is this cause for concern or is this end play normal?

My Tb has 165,000km, 4x4 and recently I rebuilt the disconnect, trans fluid exchange, struts/shocks and rotated the new tires. These humming sounds precede the above mentioned maintenance. I am happy to say though that the sway bar end links and ball joints are still in good shape...... at least.....

I am leaning heavily towards new front bearings

 

[BrianF]

And further, the front and rear diff gear oil were changed over to amsoil at 130k as was the TC with autotrak 2.

 

[kickass audio]

Usually when this happens (see plenty of other threads about it) it is the front bearings that are shot. Since you have 4x4, have you checked the front CV shafts for any play by grabbing them and trying to wiggle them? What I have found from previous experience is that with CV shafts, when they go out the sound gets louder but when a bearing goes out, it gets a higher pitch to it when gaining speed. Again just my experience, others have reported it to be different than I stated. When you turn the wheels by hand, do you feel equal resistance from one side to the other? I found that only with my bearings off the truck and spinning them in my hand that one of them was "skipping" where when I spun it you would feel a lot more resistance on a few spots than in the rest while spinning it around.

I strongly advise that if you diagnose further and determine your bearings are to blame, replace them in pairs if you can afford to do so. I mis-diagnosed the bearings on my envoy where it would get louder when making right turns and get quieter on left turns. Usually that indicates the drivers side bearing on its way out but it was actually my passenger side front that was shot. I wound up replacing both though after finding the one was bad and the other wasn't too far away from joining in on failure.

Quick question. Another thing I noticed with wheel bearings is that if there is one failing, you will notice that feeling in the brake pedal that is the exact same feeling you get when you slam on your brakes and start to skid and the ABS kicks on. I noticed both on my envoy and my dads tahoe that when both our front bearings were starting to fail on us, when we were at low speeds under 20mph the brake pedal would make that grinding noise and you could feel it in the pedal as the ABS kicked in for a second. It would stop pumping the brakes after that second but it would do that once in awhile. After we replaced the faulty bearing it stopped doing that. So let us know if your pedal randomly has the ABS engaging.

 

[BrianF]

I am definitely suspecting the front bearings for the howling noise. And if one is gone I intend to replace both. But of course it now it generated a very loud and squeaking noise, I suspect from the rear. It does not do it in reverse, only in forward gears. I first thought a rock or debris caught in the brakes but the sound does not change while braking, only when coasting does it subside. You apply torque and the sound comes back. It sounds like something rotating and is speed dependent.

I finally broke down and will have the local dealer do a diagnostic on these issues. I just dont have time to dick around this time. I will update

 

[kickass audio]

The squeaking may be something with you can track down if you rock the truck side to side and up and down from the front and back. I know with mine since I upgraded to the z71 springs, those stupid rubber dampers on them that cushion the soft part of the spring make a little squeaking noise when I go over a hard bump and the back end bounces a little. Never hear it inside the truck but it is noticeable outside and I am contemplating taking those bumpers off and seeing if that "clatter" other members claim you get with those is true. Stuff like that is hard to figure out unless you have someone go forward for you in your driveway or a big parking lot to diagnose it while in motion.

 

[Texan]

The end play on the rear axles is normal. Possible U joint on rear drive shaft?

 

[BrianF]

so they got the girl looked at. the howl is a front bearing which with beer is easy enough to change out. The squeaking was a u-joint that is on its way out. I started to figure this but the joints still did not exhibit any play from worn needle bearings. The engine codes were the usual air injection solenoid which I was not too interested in changing a year ago as well as the steering wheel position sensor.

Now with this sensor does it throw a P code or C?? I never pulled a code that was listed as P for the sensor. But either way I got a bit of work ahead. But at least the techs diagnosed the problems and now the wife will stop nagging me that I dont know what i am doing....

 

[PProph]

Good luck with that u-joint, you will need heat to get rid of the nylon inserts. I ended up needing heat and a press because gm are a bunch of #!%@#$!@$...

 

[BrianF]

Perhaps then I will dump it at a shop for the u-joints. I never liked doing them. ever.