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Loud wooing in front end... Help!

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HummDinger

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United States
Some background: 06 hummer h3 with 110k, 35" mickey Thompson atz, leveling kit and I do quite a bit of wheeling but nothing real crazy (I live in Michigan).
So I started out with a loud wooing noise coming from the front axle area on deceleration. I couldn't pin point the problem by driving it down the road so I put all 4 corners up on jack stands and put it in drive, speed up to about 35mph and then decelerate by simply letting my foot/hand off the gas.
In doing so I was able to listen to each part of the drive train with my stethoscope. Nothing sounded bad on deceleration until I put my stethoscope on the front differential, then putting it under the driver side carrier bearing I could here that the wooing was very loud right there.
So with this discovery I proceeded to change the carrier bearings out, put it all back together to find no change in noise.
Scratching my head (while reading these forums) I decided to go ahead and purchase a new half shaft for the driver side since the noise was definitely coming from the drivers side. Changed it out and still the same wooing bearing noise on deceleration that does not change going around a corner or hard turns left or right, so it shouldn't be a wheel bearing right?
I decided to take the front Driveshaft out to see if it made a difference and it did, the noise seemed to had disappeared.
So with this new found knowledge I decided to purchase a new cv for the prop shaft as well as a new u-joint, put it all back together and the noise is still there and getting worse/louder it every trip to work and back (bout a 45miles round trip) and I'm not real sure where to go from here.
Any help/suggestions would be greatly appreciated.
Thanks so much for your time and effort
 
4speedfunk

4speedfunk

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You crawled under a running vehicle sitting on jackstands? That's gonna get you a Darwin award for sure!

My guess is a pinion bearing. H3 front axles are famous for pinion bearing issues (among all the other problems they have).

And no...you wouldn't necessarily get the noise with the driveshaft out. This is because you have removed the resistance (load) that the pinion bearings normally get. During normal driving...the pinion gear is actually trying to climb up the ring gear, and screw itself deeper into the housing (on acceleration). Conversely, it tries to climb down the ring gear and un-screw itself away from the housing (on deceleration). This is because the twisting force is always connected to it, coming from the transfer-case...either in the form of clockwise twist (power application), or counter-clockwise twist (compression braking) from the motor. Take that away, and all you have is the front wheels driving a free-spinning yoke with almost no load on it, other than its own parasitic losses. Its very possible that the noise goes away because there is near-zero load on the pinion bearing. Also without a driveshaft...the front wheels spin the yoke constantly from the coast side of the teeth, and this occurs continuously...regardless if you are on/off the throttle. This would keep the pinion gear pushed tight to one end, and any slop would never be noticed except when backing up. However with a driveshaft in place, the load constantly alternates from coast to drive side of the teeth, every time you get on/off the throttle. So any slop in the pinion bearings would be very noticeable in the form of wooing, whining, or grinding. If bad enough, you might even feel or hear a small "clank" during the transfer from drive to cruise to coast.

When you had the carrier out...Did you try to spin the yoke & pinion? Did you feel any "rattle" at the yoke? It should feel nice & tight, and it should freely rotate with your hand but you should not be able to "spin" it like a top. If you could...you've lost pinion bearing pre-load. If someone has replaced the pinion seal...its very possible they disrupted the bearing pre-load. You should always install a new crush sleeve and re-torque the pinion nut to spec when swapping a pinion seal. You'de be surprised how many mechanics don't do this.
 
H

HummDinger

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4speedfunk, thanks so much for the knowledgeable response.
I did spin it by hand when it was apart and it did spin quite freely (very little preload) but no movement side to side and it felt smooth, no grinding or crunching... Maybe it wasn't bad enough to notice by hand yet. At any rate, I think that will be my next thing to replace. With 110k on it anything I Replace is warranted in my mind.
If I take the front drive shaft out do you think it would be OK to take on a 700mile round trip? Or is that to far being in 4lock?
Thanks again
 
4speedfunk

4speedfunk

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Yeah...free spinning the pinion by hand means its too loose. Its sort of a judgement call between "no play" and "proper pre-load". Pre-load is a hair tighter (a blonde one) than "no play". -Haha.

Ideally you need to measure it with an inch-pound torque wrench (with a dial on it). You'll need a BMF Pipe wrench to hold the yoke while you crank on the pinion nut with a breaker bar. The proper procedure is to remove the carrier (again) and tighten the pinion nut slowly...checking the pre-load after every pull...until you hit the sweet spot. With no ring gear installed, the freely rotating pinion should have around around 10 to 15 in/lbs. of drag on it as you spin it and read the gauge. It will take some muscle...upwards of 120 ft/lbs. of pull on that breaker bar to even get the nut to move. Once it does...tighten it in very small steps and check the pre-load often because the crush sleeve has a very narrow crush range and its easy to over-shoot it. When that happens, the crush sleeve is toast and it should be replaced. NEVER BACK-OFF A PINION NUT TO ACHIEVE PRE-LOAD. It must be achieved as you tighten it. If you catch a loose pinion early...it can be tightened and prevent further damage.

I normally don't recommend stuff like this but, since you are rather high mileage and you'll probably have a tear-down in your future...I'll go ahead and throw this option out there: Its quite possible you can simply grab the yoke with a large pipe-wrench, and put a breaker bar on the pinion nut and tighten it without disassembling anything. I have done this before on other vehicles and it fixed the whining noise. Its not technically the correct way to do it but, you might give it a try if you feel confident it is simply a loose pinion bearing. You should do this in very small increments....re-connect the front U-joint to the axle...and go for a test drive after every pull. Repeat this redneck procedure...and keep tightening it until it quits wooing at you. Just remember...you can't loosen it, so do it small steps. The numbers we're talking about here are very small...so it shouldn't take more than 4 or 5 degrees of wrench rotation to reach your pre-load. I've had axles run quietly for YEARS after doing it this way, even though it seems hill-billy.

Lastly...I don't think the t-case cares if you pull the shaft completely and drive around for a year in 4HI-Lock.
 
H

HummDinger

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Thanks for all that. I will give it the redneck treatment tonight and see if that makes the noise go away and then plan a replacement in the near future. Still a little green to the h3 and all its weak points so I really appreciate your help. Any suggestions on what brand bearing to get?
 
digglesworth

digglesworth

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illinois
this thread comes at a perfect time for me. im having a similar issue and pinion bearing sounds like it could be an option. my noise happens while "coasting"... not really accelerating nor decelerating. mostly noticed while having gentle pressure on the pedal to maintain a constant speed. accelerate, it goes away. let off the gas, goes away. it seems like it doesnt happen when theres load on it. decrease/remove load or torque and i get the spinning metal (bearing) sound.
 
digglesworth

digglesworth

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And a good axle guy....... Had a local shop quote a buddy $700 to put a locker in his xterra. And that was just labor. No parts.... Ridiculous!
 
4speedfunk

4speedfunk

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Around here...diff work starts around $250 and goes up from there.

If you have an axle that is known to be good, and all you want to do is swap gears, or upgrade to a locker...it can be pretty cheap. This is because you have a "benchmark" and you can simply use math to adjust the shims to set the pinion depth. However, if you start with a blown diff or an empty housing, the price can increase pretty dramatically. Empty housings require some special tools, and some additional measuring to get them set up properly. Most axle guys have all the tools...stuff like case spreaders, set-up bearings, pinion depth gauges, torque wrenches, etc. These are not cheap tools, so I'm sure that figures into their price.

Most of all it requires EXPERIENCE. I know several guys here in the Indy area...but I only trust two of em. These guys do set-ups all day, every day! I used to do my own stuff but, I was slow and didn't have many of the specialized tools. So nowdays I just take my axles to these guys and let them do it. They work faster. They do a better job. And I have more confidence in them than I do myself.
 
digglesworth

digglesworth

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Yeah. This was to just swap the old carrier for a locker. I dunno if they were using the old races/bearings or pressing on new. Using the old ring gear cause he wasn't regearing. I don't know if they had to drop the diff out or could work it in the truck. It was a rear so I'm sure they could leave it in. This was with them doing all the work too. Not just dropping the axle off to them. Either way, I heard that and almost spit my beer out on him. Lol
 
H

HummDinger

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update: i went ahead and had the pinion bearing replaced, inner and outer both with new races and a new crush sleeve and seal, and the noise is still present and has not made any big change in noise. It definately sounds like its coming from the front but is it possible an output shaft bearing on the t-case could sound like its coming from the front end? I'm really at a stand still right now and hate to keep throwing parts at it. The wheel bearings seem solid and the noise does not change when cornering in either direction. Any more Ideas?
 
digglesworth

digglesworth

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I think mine was a tiny little rock between the caliper and rotor... I took my wheels off to clean out all the mud and leaves from each corner. Pulled the rock out and I haven't heard anything since. Lucky me I guess.
 
4speedfunk

4speedfunk

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I guess I'll just wait for something to explode or fall out
Click to expand...

Been there. Done that. Such is Hummer ownership.

Only other cheap and easy issue I can think of, is the CV on the driveshaft. Everything else is hard to determine and costs mo money.
 
4speedfunk

4speedfunk

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Hmmmm. There are so many things it could be. You've already inspected the front diff & driveshaft...all good, right?

Have you drained the t-case fluid and checked it out? Mine was beyond nasty at only 40K miles...full of metal particulate. It was toast and I replaced the entire unit. But, it didn't make any noise like that. It was more of a catastrophic BANG and POP sound, in 4HI-Street under 10 mph. The condition of the t-case fluid can tell you a lot. Look closely at it. Smell it. Feel it. If it seems really dark, shimmering, and smells burnt...its not a good sign.
 
Last edited:
amrg

amrg

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4speedfunk said:
Hmmmm. There are so many things it could be. You've already inspected the front diff & driveshaft...all good, right?

Have you drained the t-case fluid and checked it out? Mine was beyond nasty at only 40K miles...full of metal particulate. It was toast and I replaced the entire unit. But, it didn't make any noise like that. It was more of a catastrophic BANG and POP sound, in 4HI-Street under 10 mph. The condition of the t-case fluid can tell you a lot. Look closely at it. Smell it. Feel it. If it seems really dark, shimmering, and smells burnt...its not a good sign.
Click to expand...
Any writeup on how to drain the case? Ive replaced trans fluids but not the case before.
 
H

HummDinger

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I did drain some fluid and checked it out, no shimmering and smells fine. I did change the fluid about 10k ago but i did not know about filling it through the speed sensor (thanks 3rdH3), could running it for 10k with abouut a third of a quart low cause the some bearings to go out, namely the front output shaft bearing? Also i did replace the prop shaft CV and u-joint when the noise started as i was trying to eliminate the easy stuff first.

I'll keep updating as I go but thanks to all for your thoughts, time and efforts.
 
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