Help! 2001 Tahoe grinding in 4 wheel drive

Hi,
I have a 2001 Tahoe with about 70k on it. Yesterday, when engaging 4 Hi on snowy-icy roads, the front end started making a grinding-howling noise. It
goes away when put back in 2wd and also makes the noise, although not as bad, in Auto. I drained and refilled the front diff. The level was a little low and there seemed to be some shavings in the oil as it drained. I refilled with new synthetic lube and the noise is still there. There seems to be a very slight leak on the left axle seal, however I don't know if that would have anything to do with it. Just wanted to give all of the info.
Does anyone have any suggestions on where to look to find this problem? Has anyone heard of this before? I only bought the truck this spring and tried the 4wd in all modes and everything seemed to work just fine then. Winter is coming and I need to get this fixed. Any advise would be greatly appreciated.
Thanks in advance,
Jason
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I had a 2000 Yukon that did the same thing. Also had a 2000 GMC Sierra 4x4 that did it too. There was a slight grinding noise, mainly when turning but noticeable other times too.
I had both looked over at my GMC dealership, and both times they said it was "normal" and nothing to be worried about. They even gave me a copy of a service bulletin that said that some grinding noises from the front end are normal when in Auto or 4x4.
You might check with your local Chevy dealership and ask them if it is normal or something that needs to be looked into further.
CJM

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oly wrote:

Yes, we see these problems all the time. It is true that it's normal for a certain amount of driveline noise when you engage 4hi. But if you start getting fairly loud grinding/howling noise when you engage 4hi, it often is a good indication that you have a problem in the front diff. It's very common (I've done 3 front diffs in one week) for the front diff right side bearing to pack it in. Usually, when you drain the oil, you will see fillings all over the magnetic tip of the drain plug.
Big money, and the front diff problems can also cause damage to the clutch pack in the transfer case if left long enough.
Ian
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Yes, there were plenty of shavings in the oil. The more I research and the more think about it, I am pretty sure it is the front diff. How much is "big money?" Is this something a independent garage can handle or do I need to take it to the dealer. I usually do most of my own work, but looking at the shopkey, it looks like it will take more time than I have and more special tools.
Thanks,
Jason

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oly wrote:

Any shop that is competent and confident about rebuilding a front diff on these trucks should be able to do it. It will be up to you to figure out what shop can do that. The dealership should obviously be able to do it as we are repairing these diffs all the time. We aren't allowed to just replace units, we have to rebuild things, so we get a lot of experience at it.
Rebuilding on of these split case aluminium front diffs is slightly different then doing a rear axle style...but the concepts are basically the same.
Labour would be about 7.5 hrs and whatever the cost of pinion bearings, side bearings, pinion seal, crush sleeve, bearing adjuster locks...is...etc.
Ian
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