2003 Z71 4.10 Front Differential Noise

I see a few other threads started on this but my avalanche just starting making a grinding noise from the front end. We had some snow and I had the truck in "auto 4-wheel" and could here the grinding now and then. The next day I took a look at it and when in "auto 4-wheel" I could not hear the grinding. I then realize it must of only been grinding when it was actually engaged in 4-wheel. So i put the truck in 4-wheel high and the grinding is constant. So in two wheel drive it is fine. I then put truck on lift and ran it in 4-wheel with tires off the ground and no grinding it sounds fine. Is it the front differential and it can only hear it when under load ? So in two wheel drive everything is fine but in 4-wheel under load it grinds. The fluid does look a little "whipped" but not horrible? Thoughts ?

When in 4wd it will make more noise especially when on dry pavement making turns. That of course is not good for the drivetrain and is warned about in the owner's manual. Some noise is normal when on slippery surfaces though too.
If you do not know the maintenance history of the AV you may want to change the driveline fluids since it is a 2003 and look for metal bits in the fluid to get some idea if the parts are broken or worn.

As Vaeagleav posted, I would plan on changing the driveline fluids, at the very least.

Start with the front diff and don't forget to always remove the upper "fill" plug first, then the lower drain plug.

The drain plug will be magnetic and if you see quite a bit of metal clinging to the plug, you know you are most likely looking at part of the problem.

My EXT is all wheel drive and the front diff is always engaged and under load.

From the first day I bought the used truck, it had made a good deal of noise from the front end area.

But not much more than my 4WD Explorer, so I wasn't too terribly concerned.

At first, I did not give it much thought, knowing the entire driveline was engaged and under load all the time.

However, the front end noises increased over time and when I had the truck in for a complete driveline fluid change, we saw the front diff drain plug was coated in metal shavings.

The fluid change did nothing to quiet the growling.

A complete rebuild of the front diff solved the problem for me.

New gears, bearings and the whole smack.

Now the only noise I have is a slight whine from the transfer case.

We saw no metal when the transfer case was drained and refilled and the noise is slight, so I am inclined to just let that roll for a while.

Your noises may be coming from somewhere else, but it certainly can't hurt to freshen up the front diff fluid.

EXT4ME - how loud / bad / obvious was the front diff noise? Where / who rebuilt the front diff for you and how much? Did the same place that rebuilt it do the removal and install or did you have one place remove it and send it out for the rebuild?

The noise could be described as a growl.

It was not obvious where it was coming from when I first got the truck, but it was there.

There were several things I had replaced during the first few months I had this truck.

Most things I had on my to-do list, since the truck already had 116K miles on it.

I had the front wheel hubs replaced early on, and a little bit of the noise went away, but not all.

The truck also had some fairly worn E-Series tire on it when I bought it.

When those were replaced, a lot of the noise went away, but not all.

At one point, I had the transfer case and front diff fluids changed and I had both front axle assemblies replaced.

All of this was done to chase down the noises coming from the front end of the truck.

It was at that time, when it was obvious by the amount of metal on the magnetic drain plug of the front diff, that quite a bit of wear had taken place inside the diff.

I did not have the front diff rebuilt, at this point.

After this work, the noise was less, but still there and in short order, the growling began to increase.

I then had the front diff completely rebuilt with new gears and seals.

99% of the noises went away instantly.

Since that time, I still had some noise coming from the transfer case, but not much.

Certainly not enough to cause concern or make me want to have the TC rebuilt.

I checked my files and it shows a bearing kit @ $149.90, OEM 3:73 gear set at $389.99 and 2 quarts of Mobil 1 gear oil at $21.98.

I had the front diff work done and had the power steering pump replaced at the same time and the labor was $1150.00 for this trip.

I can't tell you what just the front diff would have been.

The power steering pump was shot, so I just had them do them both while I had it in the shop.

If I had the money and lived closer, I would buy that EXT off of you in a heartbeat.

Mine, especially after spending a ton of money early on, has been the best truck I have ever owned.

Period.

Best of luck to you.

And, I had all of the work done at a local independent mechanic that I have used for many years.

He usually gives me my parts at his cost and I get a 10% break on his labor since I return the favor by working on his computers, when needed.

He removed, rebuilt and replaced everything in his own shop.

Seeing the front diff all laid out on the bench, I was a bit surprised that it was as small as it was.

What I know?

Did your $1150 include the gear and bearings, os was that on top of the $1150?

When did you have the front diff done, and how many miles do you now have? Has it gotten louder as you have put more miles on it?

The $1120 was the labor for the rebuilding of the front diff and the replacement of the power steering pump.

I listed the parts cost in my other post.

I do not have a breakdown of the cost of each labor charge.

I just rolled over 209K this week.

The EXT had about 150K on it when I had the front diff rebuilt, so we now have close to 60K on the rebuild.

The front diff has been perfectly quiet ever since the rebuild.

The only noise I have had since that time is a low level noise coming from the transfer case that has not gotten any worse with time and miles.

The transfer case noise is not bad enough to be concerned with and I only notice it when I think about it.

I have all of the fluid levels checked at every oil change.