This is my first 4x4 so I dunno if it's normal, but when I'm driving it in 4wd the drivetrain makes a winding noise similar to the sound performance transmissions make. It doesn't sound bad or anything, but I was wondering if this is normal. My roommate's TJ doesn't do it.

BTW, it's an '88 GMC Suburban 3/4 ton automatic.

Id make sure the pinions nuts are tight and theres gearoil in the diffs and transfr case.

Cool. Thanks. I know the diff/case oil needs to be changed, but there's definitely some in there, lol.

Thats how they normally sound judging from every other vehicle ive driven with chain drive tcases

That's even more encouraging. I just wanted to make sure it wasn't a catastrophic failure waiting to happen.

tjs have chain driven tcases to... your chain may be stretched and therefore hitting the top or bottom of the case... check and see if there are any metal shavings in the oil.