2003 Tahoe Front End Howl - Can't find it!

It's really got me. I can't find it and it is driving me nuts...

2003 Tahoe 4WD, 91,000 miles. I am hearing a howl from up front that is audible anywhere after 20mph or so. I hear it in 2WD or 4WD, it doesn't matter. Hear it driving along, coasting or braking. It is not motor related, I even put it in neutral and shut the motor off to prove I still hear it. I also believe it to be dragging down the gas mileage, so I'm pretty sure it's in the driveline.

-I thought it must be a hub, but there is no play in either one, and nothing unusual when rotating by hand.
-Thought it might be a tire, so I rotated them front to back - no change.
-Changed the front differential oil - no change.
-Changed the transfer case oil - no change.
-Dropped the front driveshaft and the u-joints seem fine, no play, not frozen.
-Rotated the front differential yoke by hand while driveshaft was down and don't feel anything disturbing.

I'm fearing that it is inside the front differential and is going to be more than I can fix myself, but would like to prove it before I take it in. I have previously changed one hub that started grinding and am tempted to change the other as it seems logical, but there is no play in it and feels fine.

Thought about the drive axles...willing to change them, not a bad job, but hate to just throw parts at this thing and still end up with a bad front differential.

So I'm really hoping for some advice on what this could be, or how I could better find my problem. I feel I can replace most all of it until I get into that differential, that's probably more than I want.

Sorry for the long post, thanks in advance for any advice, words of wisdom or suggestions. John

There is no way from here to properly diagnose road noises as you can understand. Does it change driving in figure 8 patterns to vary the loads on the ft bearings.

It doesn't seem to change on curves or turns, but I have not done any tight figure 8's. I will try tighter turns tomorrow.

Yea I know it's impossible to diagnose over the internet, just hoping someone had something similar...grasping at straws. Or maybe hoping to find out if a front differential problem is common or rare?

John

Too late now, but did you see any fine metal debris in the diff fluid?

Some. Not anything I felt was a big deal, but yes, the magnet had some filings. John

the front hubs are a big failure item on these.

remove the speed sensor check on the hub grease. check that the hub is not leaking grease out the rear seal. the hub having some play would be when its really bad .

when turning at 20-40MPH and it gets loader it is a hub.

I and others do pump grease into these hubs @the sensor hole and they then last much longer. if one hub is bad then so is the other.

some in snow country replace these every 3-4 years...esp china crap hubs..

I have suspected the hub all along, and I did have to change one already due to it grinding. Maybe I will go ahead and change the second one to see if that does it. I'm keeping the truck so it would need it soon anyway if it isn't bad.

Thanks for the replies!

John

Don't overlook the tires and alignment as a source/contributor to the noise. If the tires are not directional you might consider rotation in an "X" pattern to get them into new positions. Tire wear can impart load on hub bearings just as incorrect toe and camber can load bearings oddly. The constant thrust load from either can cause wear and noise.

Should have gone with my gut earlier. I changed out the hub that I dodn't do last time and the noise is gone. Thank goodness.

I really figured it was that hub, but honestly couldn't feel anything wrong with it. Obviously it was on it's way out and I just couldn't tell.

Thanks for the input on this thread! Things worked out.

John

Based your info, I'd say the ft diff has a bad bearing, pinion bearings are the most common failures in ft diff. Of course Blue Bowties advice should be tried first.

so now you are a hub expert on these.
the hubs as I stated before do require some grease to be injected into the sensor hole. also the sensor hole may over time need a cleaning to remove rust. this rust will push out the sensor so little that , it reduces the output volts at slow speeds which then causes the abs to act up.

to reduce this rust I put a sealer over the sensor so corrosion is reduced to stop this since this if it does occur , will cause you not to stop , at slow speeds.

when spinning the hub by hand at a good speed ac volts should be .35-.6volts/ 350mv-600mv.. any output around 300mv is where abs sh*t happens.. these do rust quickly in the rust belt.

[quote=jjwg3;7196280]It's really got me. I can't find it and it is driving me nuts...

2003 Tahoe 4WD, 91,000 miles. I am hearing a howl from up front that is audible anywhere after 20mph or so. I hear it in 2WD or 4WD, it doesn't matter. Hear it driving along, coasting or braking. It is not motor related, I even put it in neutral and shut the motor off to prove I still hear it. I also believe it to be dragging down the gas mileage, so I'm pretty sure it's in the driveline.

-I thought it must be a hub, but there is no play in either one, and nothing unusual when rotating by hand.
-Thought it might be a tire, so I rotated them front to back - no change.
-Changed the front differential oil - no change.
-Changed the transfer case oil - no change.
-Dropped the front driveshaft and the u-joints seem fine, no play, not frozen.

I'm fearing that it is inside the front differential and is going to be more than I can fix myself, but would like to prove it before I take it in. I have previously changed one hub that started grinding and am tempted to change the other as it seems logical, but there is no play in it and feels fine
[quote]

on your drive train fluid work. do the transmission fluid/filter DEXRONVI ONLY . then drop the rear diff cover and clean out the diff using low odor mineral spirits. replace ALL the drive train fluids every 40K miles.