hum or howl in 4wd

[Doubeleive]

this has been a historical issue on the gmt800's some of the front diff''s are just noisy period..
I experienced the same (noise in 4wd) and there was no indication of anything being bad, miles and miles and miles, always worked fine, just noisy when engaged
no metal shavings, no leaked out fluid, no play in anything, just noisy.
have not really heard of it happening on the 900's though until now.

 

[Charlie207]

this has been a historical issue on the gmt800's some of the front diff''s are just noisy period..
I experienced the same (noise in 4wd) and there was no indication of anything being bad, miles and miles and miles, always worked fine, just noisy when engaged
no metal shavings, no leaked out fluid, no play in anything, just noisy.
have not really heard of it happening on the 900's though until now.

I would have been fine with the noise in my front diff, but it was getting worse and worse, and the fluid was clearly full of bearing material - lots of sparkles accumulating after fluid replacement and almost no 4WD engagement.

I have the bad unit sitting on my workbench, and I'm not sure what to do with it. I could probably pull it most of the way apart, but I don't have a press to reassemble, or the desire currently to fire the parts-cannon at it.

 

[DaveO9]

I had my wife drive it tonight so I could sit in front pass seat and rear seat to listen. Still don't have it nailed down, but I think I can rule out t-case. It's most noticeable from driver's seat. I've got 207k with what I'm assuming are the original front hubs/bearings. If the noise isn't coming from the wheel bearings, no worse off since I should replace them anyway. If I still have it, I'll have to think about replacing the front diff with another used unit. But I am curious about the possibility of it just being a normal thing for these front diffs. It's not a super obnoxious noise. My subaru had bad rear wheel bearings when I bought it - that noise was crazy obnoxious. Most of the time in 4wd in the Tahoe, it just sounds like I'm running knobby mudder tires up front.

I'll report back after the hub replacements. Might be a month or two.