I have a 2004 Chevy suburban 1500. Just the other day when we got some ice on the road I put it in four-wheel high . It started to make a humming sound from the front end while in four-wheel drive. But only when I was stepping on the gas. If I let off the gas the sound would go away. I put it back in two wheel high and the sound is not there. Could it just be the differential and the front is low on fluid? I don't feel like it would be a wheel bearing because wouldn't it do the same sound in two-wheel high as well? Any help is appreciated.

 

Get under your rig and check the fluid. If low, fill it. If that keeps occurring and the fluid was real low, you need to repair or replace the axle, as it is not your bearings or CVJ's. You've seen no indication that it was not leaking?

 

So I was just out underneath it and it was about a quarter of a quart low. Which doesn't seem like very much but I topped it off. No leaks that I can see. Both the front and back differentials are dry and clean. I'm curious if these older suburbans are just louder when there in four-wheel drive? Seems odd that it only makes the humming sound when I press the gas.

 

I have had several 4WD's, including a Jeep that had a T/C with manual locking hub's.They will make a bit more noise in 4x4, then 2x4 particularly a Jeep CJ-5 that was intended to be driven off-road and it was, but it was not that much more noise, even with the hubs locked in.going straight with a 4-speed stick. The Jeep I had even had an undocumented Borg-Warner 205 T/C that had a 2x4 low setting, which I have never seen since. I cant explain the gas issue.

That's not occurred on my 98' Chevy K-1500 no matter what. I can put the gas to the floor in 4x4 with my 5-speed stick,and I only hear it making a little more noise that is not a whine, but I don't know about a newer Chevy Suburban.I'd recommend pulling the axle cover off and checking out the spider-gears. That way you could see if something is amiss, as well, as getting rid of any excess metal wear from break-in or other with a magnet. My apologies and you have already done that. It's a mystery like my 2x4. Sure made backing up slow in a parking lot easy as pie !

 

whenever you hear a noise "from the dash" or "from under the hood"

1) get out check all the lug nuts are on and tight

they can make a wide variety of noises (depends on car model and so on)

good to year you were low and got it solved.