Tahoe 4WD Howling Noise

[JLaud]

First of all I'd like to say this forum has been a wealth of knowledge and a great help to me, been lurking around here for a few weeks now ever since i got my 2003 Tahoe Z71. Used the how to's to do the rear brakes, Intermediate Steering Shaft, DRLs, belts and other misc items.

Went for a drive with the family yesterday up I-70, hit the snow storm and used 4WD. Everything worked great but there seems to be a growling/humming noise like I've got mud tires only when slowing down/coasting between 35 - 25 mph. It's very quiet at all other speeds. This happens whether I'm on the brakes or not, tranny in neutral or drive. It happens in both Auto 4WD and 4Hi mode, and goes away in 2Hi. It's also kinda intermittent, does it only when its warmed up and not when its cold, and there are times when it doesn't do it at all.

Did some research online and the only thing that came up with similar symptoms was unevenly worn tires between the front and back causing the driveline to bind up a bit. My tires aren't the best, they are a bit unevenly worn between the front and the back, figured since its going to be summer I will hold off on buying new tires until the fall.

Truck is very quiet with no noises or sounds in 2Hi or when accelerating in 4Hi or Auto 4Hi. Come to think of it, I've only got 2 strange noises in my truck, this 4WD noise and a noise from the back like a screech or squeal when going over speed bumps or dips. Searching online, most people think this is the slip yoke that needs to be greased. My folks' 03 Suburban makes the rear squeal noise as well.

I got it serviced a week ago and everything checked out, no leaks underneath and the CV axles look good.

Sorry for the long winded post, figured I'd give you guys as much info as possible. Appreciate the help in advance.

 

[Jay]

First thought is carrier bearings... the 8.25" IFS is known for eating these and the problem usually shows itself in the form of light throttle and coasting situations at 30-45mph in Auto 4WD and 4Hi. AWD versions of our trucks have the most issues.

I hope this isn't it, but from the description it seems accurate. When the front diff was drained, whoever did it should have noticed metal shavings.

Just so you know, the front CV shafts ALWAYS turn in our trucks (regardless of drive mode), but the front differential and driveshaft do not since they are disconnected at the front passenger side axle tube in 2WD (crawl under there, you will see a little motor assembly on the passenger side the front differential). In Auto 4WD the front encoder motor locks the front axle in, making the whole front drivetrain turn with the tires including the front driveshaft. However, the driveshaft is not connected (being driven) at the transfer case. It's like being in 2WD with the front axle turning, but not powered... this way when the computer senses need for 4WD it just engages the clutch pack in the transfer case.

If you are only getting the noise in Auto 4WD or 4Hi at these speeds, the problem is inside the front differential or the driveshaft. 90% of the time it's the carrier bearings. Been there a few times myself... the front diff isn't that hard to rebuild though.

 

[01HDtahoeNJN]

Had the same problem ..mine happened to be the bearings

Sent from my SCH-I500 using Tapatalk

 

[JLaud]

Thanks for the replies. I was just thinking that bearings usually make noise whether accelerating or not and the noise usually increases with speed, since there is no noise in any speed while accelerating, only when coasting and only between 25-30mph, figured it may have been the front driveshaft u joints or something like that.


I was hoping the carrier bearings weren't the issue, but guess thats how it goes. Any idea of how much it costs to get it rebuilt, or is there some guide on how to rebuild it. I can do routine maintenance on my vehicles but not skilled quite enough to tackle a diff rebuild.

 

[Jay]

As long as the gears are still good the cost for parts isn't high. You can get a good quality rebuild kit with Timken bearings for under $150. Make sure you get the new locking tabs for the spanner nuts from an 07+ truck (cheap at GM dealer... tell them 07+, don't let them source the old style). The older tabs were very prone to failure... in fact I'm willing to bet if/when you tear it down you will find one or both tabs broken off. Which lets the preload dissipate and since these are tapered needle bearings, they will eat themselves alive.

If you don't have access to a GM service manual you can try finding the original AAM service manual.

Just did a google search while typing and found this: http://www.truckmodcentral.com/forums/showthread.php?t=13813

One of the best internet articles I've ever seen for the 8.25". If you take the parts to a reputable shop I don't imagine they'd charge more than 5-800 to do the job. Wouldn't hurt to get a few quotes though.

 

[JLaud]

Thanks for the info. I'll have it checked out. Might hold off on doing this until later since it doesn't do anything in 2Hi and being summer I won't be using 4WD for a while.

But, I've got another issue that's popped up. Did a lot of searches on this forum and the internet but didn't turn up a lot. I've got this hissing/whining/whistling noise from the steering wheel only when turning left after engine has warmed up going slow like into the driveway or in parking lots. It does it even when the truck is stopped and if I turn the wheel left and hold it. Checked the PS pump fluid and it looks clean and full with no leaks. Reading online, people seem to think that it's the Steering gear since it only does it when turning left and not right. The noise is not heard from outside the truck, only inside.

You guys have any thoughts on this? If it is the Steering gear, it doesn't look too difficult to replace and it's not overly expensive, but don't want to just throw parts at it. Thanks for the help.