Loud Whine in 4wd and Auto 4wd

adbaker · January 13, 2012

Hi Everyone, last two days we've had some crappy roads to deal with, snow, ice, etc.. Anyways, the truck has developed a loud whine under acceleration or cruising speed (i.e. cruise control). It's definitely a whine, not a squeal, or grinding. If i let off the gas it quiets down. This morning i did some experimenting on the drive into work. There is no whine in 2wd. The whine sounds the same whether i'm in 4wd or using the auto 4wd. I can actually be cruising down the road in auto with the noise, hit 2wd and the whine stops. It gets louder, the faster i go. I can't hear any noise when i'm cornering, but it could be just that its too low of a noise and slow speeds.

Trucks a 2004 Silverado Ext with the Z71 package, stock, no lift or leveling kit.

I haven't had a chance to crawl under yet but with the weekend coming hopefully i will. Any ideas where i should start looking?

Thanks

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Stevens03 · January 13, 2012

Well, I'd check the obvious and make sure you have plenty of fluid, u-joints and CV joints. Otherwise you could be looking at the early stages of a bearing going out.

peteking · January 13, 2012

My 2005 does the exact same thing....though I don't believe it's as loud as what you are describing. But definately a "whine". I did change out the diff fluid and lubed every joint I could find about 15000 miles ago....and that helped.

adbaker · January 13, 2012

Thanks for the quick replies, fluid check first, easy one to do, didn't even occur to me...i need coffee!!! I was thinking/hoping u-joints. This summer i replaced the two u-joints in the rear it was more of a squeak or squeal but i'm hopeful 'cause that would be a pretty cheap fix. If it's bearing (hubs) or cv joints wouldn't i hear it in 2wd as well?

@PK, it's definitely louder than normal. Now, i don't use the auto or 4wd much. But the noise started about halfway to work yesterday and was there on the way home yesterday and on the way in today. So much so that i didn't bother with 4wd except for the few "tests" i ran on the way in.

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peteking · January 13, 2012

Yeah if it was your bearings, you'd hear the noise all the time I'd think.

When my 4wd (both full time and Auto 4wd) made that noise my first thought was the transfer case. But even after doing a fluid swap the noise remained....so I've just come to accept it as normal. But greasing the U-joints on my front drive shaft is probably a good idea too.

If this thread doesn't get his reply in the next few days...shoot a PM to ChevyTech77. He's usually on the forum every day or every few days. Very friendly guy....knowledgeable and helpful on questions like this.

wilsonz71 · January 13, 2012

How fast are you usually going when it gets screaming? 4wd is always going whine a fair bit more then 2wd in any truck, it's pretty normal. But I try to not to go over 60km/h in 4x4.. Never over 80!

BlackZ71Silverado · January 13, 2012

You should hear a little whine, but not as loud as you describe. What you hear are the gears in the front diff. It is noticable because you are much closer to the front than the rear, so you can't really hear the rear at all.

By the sound of it, I would guess that your front diff. bearings are going bad if it's that loud. Check your your diff fluid like mentioned above. Also check your diff seals to make sure they are not leaking (if the yare your fluid level should be a little low), front drive shaft U-joints.

Wires · January 14, 2012

Does it only do it in 4wd/auto? Could be you'be been roasting tires (or one is low), so the diff is spinning more trying since the tire diamters are different.

I really noticed it in 4wd when the back tires were worn more, and another time when one was low in the front in auto.

BlackZ71Silverado · January 14, 2012

Does it only do it in 4wd/auto? Could be you'be been roasting tires (or one is low), so the diff is spinning more trying since the tire diamters are different.

I really noticed it in 4wd when the back tires were worn more, and another time when one was low in the front in auto.

We don't have locking front diff. It is an open diff so the front tires don't spin at the same rate. The tire diameter idea would apply if there was a front locker, that's when you would see the wheel hop.

adbaker · January 14, 2012

Thanks for the suggestions, hopefully i can get a look around tomorrow, just spent two bours blowing snow, after an hour and a half hockey game, and i'm only half done the driveway...i'm a little burnt!

First up, it's definitely louder than normal, i've always had a slight hum in 4wd or auto but this is different, and as i mentioned, it started halfway to work. It hasn't changed today but its still loud. I can hear the whine at pretty much every speed when i accelerate, again only in auto or 4wd, not 2wd. It gets louder and faster the quicker i go.

Black...My axle seals are leaking slightly (again, had them done about 2 1/2 years ago) but i barely add between oil changes, could be they've gotten worse.

Oh and the tires are new, maybe 1000 km on them.

Thanks again everyone, still hoping it's u-joints. I'll let you know what i find...

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Wires · January 14, 2012

Does it only do it in 4wd/auto? Could be you'be been roasting tires (or one is low), so the diff is spinning more trying since the tire diamters are different.

I really noticed it in 4wd when the back tires were worn more, and another time when one was low in the front in auto.

We don't have locking front diff. It is an open diff so the front tires don't spin at the same rate. The tire diameter idea would apply if there was a front locker, that's when you would see the wheel hop.

Sorry.. good point. You do get the whine from the transfer case if the front/rears are mismatched in diameter though.