H3 Howling sound during acceleration - is this bad?

mdocod said:

Lol... the T-case fluid can of worms...

The most likely reason for them to transition from speccing the Dex III to the Dex VI is the reduced viscosity of Dex VI is apt to improve average fleet fuel economy estimates.

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Dex VI would have been the quoted spec for all years but it was not yet certified for the transfer case when the 06s were released. The electronic service manuals that GM uses will specify Dex VI for all years of the H3. Unfortunately, they can't electronically update printed materials like the owner's manual. :giggle:

I think the best maintenance that you can do to the transfer case is change the fluid often. Unlike the diffs or the transmission, there's no magnet to catch any metal particles so those pieces keep floating through the oil. They may be small, but they will be abrasive nonetheless. I did a fluid change before Moab and post Moab, about 3000 miles on the oil and there was a light silvery sheen. Looks like something is wearing out in there. I've also gone 20K between changes with less metal apparent in the fluid.

There is a magnet in the t-case. Unfortunately it cannot be accessed or cleaned except during a teardown. Why it’s not on the drain plug is anyone’s guess.

The chain is steel but everything it rubs on is non ferrous anyway (magnesium or aluminum). So most of the metallic dust is softer metal that won’t attach to the magnet. It does a good job of clogging the oil pump pickup screen, however.

I'll be sure to let y'all know if the Tcase rebuild took care of my whining sound. I should be getting my truck back this week.

4speedfunk said:

There is a magnet in the t-case. Unfortunately it cannot be accessed or cleaned except during a teardown. Why it’s not on the drain plug is anyone’s guess.

The chain is steel but everything it rubs on is non ferrous anyway (magnesium or aluminum). So most of the metallic dust is softer metal that won’t attach to the magnet. It does a good job of clogging the oil pump pickup screen, however.

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thanks! I meant those, um, non-ferrous magnets weren't present :shame:

Hello Zerreitug, I have the exact same howling in my Hummer H3, in my case, I am almost sure it was the front differential. Some months ago, I rebuilt the front differential thanks to the help of 4speedfunk, that help me with a lot of information via email. I rebuilt the front differential because a loud coasting noise, but I have too a howling that sounds with acceleration in a speed range of 30 mph to 60 mph. I rebuilt the front differential with a master overhaul kit of bearings, seals, etc..from yukon, but i let the same ring and pinion, and the same pinion depth. So..after the rebuild the coasting noise is almost gone (I have a poly bushing kit in the front diff from outfitter design so I can understand a certain level of driveline noise because is not longer mounted in rubber), but the super noisy howling during acceleration is still there and the moment when it sounds a lot is when you are accelerating and achieve exactly 30 mph.

So my feelings are that I have a case of maybe warped ring and pinion...or maybe the aluminium differential allow enough flex that right now the differential is not aligned, and allow a permanent drive not aligned between the ring and pinion.

One option for me was to remove the differential and try to set up right, mainly the pinion depth but I want to know if maybe the problem is not related to front differential, and maybe is related to transfer case (because I remove the front propeller shaft and run it in 4Hi and yes! the noise is almost gone, the howling, but I can still listen it and feel it...maybe the ring and pinion running ,even without front propeller shaft, makes the noise..but maybe is the output shaft of the transfer case. (I used two differents cv joints in the propeller shaft with the same results)).

So I wait for atvspeed to rebuild his transfer case, and listen his feelings, maybe the transfer is the problem

Hope my case helps out!
Guerrero

Thanks for the input Guerrero. I too will be waiting for atvspeed's results about the transfer case.

I also noticed something else with my howling noise. Im not sure how it fits in but since my howling is intermittent, i have noticed that my brake pedal has a relatively long travel when pressed, before the brakes actually begin working. This long travel in the brakes seem to go inline with the howling. The only difference i notice with my H3 when the howling is absent, is that my brakes are very firm and responsive; but when the H3 howls, i have to press the pedal (what feels like) 3x further down before the brakes kick in.

Its pretty wierd, but these two situations go hand in hand. When the howling is absent, the brake pedal is very responsive; when the howling is present, the brake pedal has much more travel before the brakes engage.

Loose brake caliper that's sometimes in place, sometimes out of place?

Hi please tell me what was the outcome to your problem. Now I'm getting that noise you described my truck
Sounds like a jet between 30 and 45 mph. And it goes away at higher speeds and when I decelerate other than that
My truck is quiet. Thanks

JPaul said:

Sure it's not the engine fan? When the clutch is engaged the fan is pretty darn loud. More of a roar than a howl though I guess. Have any audio of the sound?

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This is quite common. Check the viscous clutch for the engine cooling fan.

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I Lost an axle seal on the front diff. during a cross trip. She roared like a banshee but got me back from Colorado to Mississippi. New front differential upon my return home.