Front (?) end grinding noise

[uconnjack]

Hi, first time poster here with a problem I can't seem to diagnose or solve. I have a 2008 4WD Avalanche 5.3L with 80K miles. About 2 weeks ago, I noticed a "grinding" noise coming from what sounds like the front end, similar to what you would hear if brake pads are getting low and starting to grind on metal. Here is a summary of observations, diagnostics, and attempted repairs I have performed:

• Sound is first noticeable around 15-20 mph and continues through highway speeds.
  
• It is constant, although it has a rhythmic pattern to it which increases in frequency the faster you go (rpms don't affect it).
  
• It gets slightly louder when I turn or slalom left, and get quieter or disappears to the right.
  
• Engaging 4WD doesn't affect or alter the noise at all.
  
• The noise does change at all when applying the brakes (other than the frequency due to deceleration).
  
• The noise also doesn't change when applying the emergency brake while moving (although it doesn't seem to work in general).
  
• My first action was to clean up the front brakes and change the pads. Rotors, calipers, pins, dust shield, etc. were all in good shape. Didn't stop or change the noise.
  
• Next I replaced the front right wheel bearing hub, based on the noise decreasing when turning right taking off load from that side (although neither side seemed to have any play or noise when hand turning). Had no effect on the noise.
  
• Since I had only bought one new hub, I switched out the left bearing hub with the old right one I had just replaced (since it appeared to be in good shape and apparently not the culprit). Again, noise didn't change at all.
  
• I checked the front differential fluid from the fill port, it was at the correct level. It looked and smelled OK, although I did not drain and check for metal filing/sludge.
  
• I jacked up the back and checked for play in the rear wheels, both sides had some, but very minimal play. Rear pads and rotors were good too.
  
• The front drive shafts also did not seems to have any appreciable play and no grinding when manually turned.
  

So now I am at a loss. The change in the noise when turning/slaloming back and forth led me to believe in was front bearings, but apparently wasn't. I suppose it could be the rears, but it really sounds like its coming from the front. I don't think it would be in the differential itself since I wouldn't think the changing directions would affect that. Maybe a front drive axle/CV joints, but those usually clunk a opposed to grind I believe? I am pretty confident its not associated with the brakes.

Anyone have any ideas or thoughts on what I may have missed? Thanks in advance!

[zzGUY46]

Maybe the carrier bearing that holds up the driveshaft going to the rear? I think thats what its called. Another guess might be the front transfer case, there was a fix I saw somewhere where the aluminum case gets worn and the fix was putting a steel piece where the wear was inside., so check for aluminum flakes in front diff fluid. sorry for being vague but I have had similiar probs and watched lots of Youtubes...lol maybe someone else will be able to explain better. I'm doing front bearings right now.

[arcasey]

First, before I say this, I'm not saying that the other Hub that you moved from one side to the other is bad but from my experience if you change one you really should change both. I have also found Hub bearings to be bad and there be no immediate signs of them being bad. The only way I knew it was bad was by replacing what I thought was a good bearing with a brand new one and all my problems went away. The only other things that could be causing your noises are the CV axles and front differential bearings because those are the only other components that I can think of that should be rotating when driving and changing speed with actual vehicle speed and not engine speed (assuming 2WD operation and not engaged in 4WD).

 

I may be wrong but I think what zzGUY46 is referring to is an aluminum clip in the transfer case that is notorious for wearing and breaking and the best fix was replacing it with a steel clip. Again I may be wrong and that may not apply to this particular model but I really think if your problem was transfer case related you would know it. When you engaged the truck in 4WD did you actually go and drive it in 4WD? How about 4WD Low Range?

[uconnjack]

Yeah, it's always possible that the bearing I switched was bad too, but I dont't think so since that would have meant both bearings went at exactly the same time which is unlikely, and the noise didn't change at all regardless. And yes, I did drive it for a while in 4wd high, no difference (not 4wd low though since you can't really go over 20mph anyway.)

 

I also don't think it's in the front differential, since I don't think the sound would appreciably change with turning. I will pull the drain though and see if there is any metal in the fluid.

 

I guess the cv/axle is my next most likely candidate since that it the most likely to change noise when weight is shifted and to make sound when in motion. Just always expected more of a clunk or crunching sound than a grinding. Easy to switch out though.

 

However, when asking my son who was riding in the back where he thought the sound was coming from, he agreed definitely on the right side, but he thought maybe from the back. Maybe the rear bearing is going? Does that happen often?

 

Just FYI, we did just get back from a 3 week xcountry trip with a camper, although this sound started a few weeks after returning. I also rented a boat on that trip and launched with both rear wheel submerged, but I can't imagine that caused any damage?

[arcasey]

If you think it may be coming from the rear I might would jack the rear end up and spin the tires while holding one hand on the back bumper to feel for vibration. Then pull the tires and the brake drums/rotors off and check to see if there is any gear oil leaking from the bearings. I would also check the U-joints on the rear drive shaft.

[nqabigt]

have the rotors checked for warping

just changed mine, and way quieter now

if stock rotors, change them

[KO Phoenix]

I have an 06 Tahoe that we picked up about six months ago and wasn't having any issues until a few weeks ago, when it started to experience the very same problem, with one troubling addition that the transfer case selector switch (push button controls on left side of dash) appears to be stuck in Auto AWD . I had asked my wife (who was driving the vehicle while I was deployed) how long the light was on and she couldn't remember. I know there is a way to manually put the truck back in 2H (as a temporary fix), but I can no longer find the YouTube video providing the steps. If anyone can point me in the right direction on this, I would be most appreciative as I need to get the truck out of Auto AWD, before I tackle the CV Axles (which from my initial post hub assembly research sounds to be the culprit). Let me add that I'm not a professional "wrencher" and am admittedly probably not well versed as the majority of other posters but this is our second bowtie (other truck is an 05 Av) and have been doing my best to learn a long the way. I will again appreciate any advice or inputs to this issue to get this truck back on the road for my wife and kids. Thx.

[dlfiscus]

I have the identical problem with my 03 Denali, with the addition of a slight tick in the steering wheel - like a small lump on a tire, but all are round and running smooth and true recently balanced. Experimenting at highway speeds, just a SLIGHT off center right will cause the noise to almost disappear, and back to center it reappears, and gets worse with left turn. Definitely front end - all feel is through the steering wheel.

I replaced the front brakes and rotors, and the right wheel hub - all with no change. Left hub was next, although I didn't think that was the problem. Now after finding this post, really don't think it is the problem. Have driven over 1000 miles since first noticing it - has gotten more pronounced, but not a lot.

Vehicle has 104,000 miles - front diff changed at 80,000 with an 05 Escalade one with 40,000?? miles.

I am leaning toward(worrying about) something in the front differential. Someone mentioned noisy clutches in the limited slip, but mechanics tell me no, GM trucks don't do that.

 

All help appreciated!

 

Don

[Kurt1234]

Wheel bearing bad my first guess. If you turn left and the noise goes away it is the right side wheel bearing. If you turn right and the noise goes away it is the left side wheel bearing.

[ifixedit]

Been there and done that with my 03. From what I'm reading here I too would agree, bad front hub bearing(s). I swear the things have built in timers, at appox. 80K miles they go bad!

[dlfiscus]

Wheel bearing bad my first guess. If you turn left and the noise goes away it is the right side wheel bearing. If you turn right and the noise goes away it is the left side wheel bearing.

Oh, Oh This is opposite of my theory. I thought grinding noise will get worse with more load on the wheel. When I turn left(put load on the right wheel), the noise gets worse.

 

What am I missing?

[ifixedit]

When the front hub bearing(s) have gone bad on my 03 they've usually been dead silent going straight, would make all kinds of weird squealing / squeaking noises turning up the driveway as an example, but then the next time not do it at all. I had one get bad enough that it did start rumbling at speed on the freeway, I'd hit the brakes and the noise would go away but then come back a few minutes later. Easiest way I found was to jack up one front wheel at a time and try rocking the wheel up and down, I found in my case there was considerable play, took the hub off and found very rusty bearings, in other words they were shot. Another indicator of bad hub bearings is if you have a lot of brake dust on one or both front wheels, or the truck pulls to one side or the other when you hit the brakes, that's also a good indication of a bad hub bearing as when the bearing gets bad it no longer holds the wheel square to the brakes / calipers and things are out of alignment when you hit the brakes, hence the pulling and excessive brake dust.

 

Just some ideas that may help.

[dlfiscus]

Think I found the problem. Front differential drain plug looks like a porcupine. Some shavings 1/4" long!

[Kurt1234]

Yep. Sounds correct.