Need help on my Silverado.. Grinding.. Whirring sound up front in 4WD

Grinding could be the differential. Could be u joints too. If you put it in 4wd and when you take off you hear like clicks or snaps that could mean the gears in the differential are ate up. Whiring noise tho could be u joints. Grease the u joint and then check your differential fluid.

Since it only does it in 4wd narrow it down to your 4wd components. Check them and then just use process of elimination.

More than likely the CV Joint gone bad.....not that you'll replace it yourself, but this describes it quite explicitly.

Cv joint is when you make turns. Turn right and if your hear the click it means the left one is bad. And vise versa.

Drive backwards & turn hard (use a car park) left or right, thats when the CV's really make a noise.

bearings also make more noise in turns, but so does bad rubber on worn tires
I'd suggest checking out a Chevy truck 4X4 forum for clues/answers

You can also put it up on jackstands and let it idle in gear, walk around it listening for the sounds, just don't get under it or be in its way if a jackstand lets loose

My guess from the sounds of it, would be a bearing within the front differential.
On the basis that I'm asuming that it is IFS and that you mention that the sounds are in 4wd, ...and not in 2WD, ...here I am asuming this as well.
I had to have a bearing replaced in the front diff. of my '03 Sierra a few years back, ...had a nasty whirring/groan sound while in 4wd and sounded normal in 2wd.
I doubt it's the CV shafts, if the noise changes from 2wd to 4wd as they are always spinning anyway

just a guess here but probably something in the front differential I doubt it is the cv joints since on a Silverado they turn all the time but there is no torque on them in 2wd it could possibly be in the front drive shaft or in the transfer case but you would probably hear/feel that under your feet more then from the front end. if you can get all 4 wheel off the ground and get someone to put it in 4wd and accelerate you can use a mechanics stethoscope and listen to the components and narrow it down

of course if you have a chevy built before 1988 you have a solid front axle and you could have axle bearings or wheel ujoints going out

I'd look towards the gearbox, have you checked the fluids in it? Might be a good time to change it. Let the first quart go into a clear plastic qt jar or something, then comb through it for metal bits, maybe just let it settle then pour it off the top till you get down to the bottom so you can know if anythings breaking loose. Also poke your finger up on there if possible to check for anything loose that didn't come out with the oil.
After that I'd look on downstream till you find it

Originally Posted by Jvcr1

My guess from the sounds of it, would be a bearing within the front differential.
On the basis that I'm asuming that it is IFS and that you mention that the sounds are in 4wd, ...and not in 2WD, ...here I am asuming this as well.
I had to have a bearing replaced in the front diff. of my '03 Sierra a few years back, ...had a nasty whirring/groan sound while in 4wd and sounded normal in 2wd.
I doubt it's the CV shafts, if the noise changes from 2wd to 4wd as they are always spinning anyway

Sounds right from here (NZ) a floating shaft with a bad bearing won't make much noise, but put pressure on it & the shaft will go out of centre & nek minute theres a % of your HP going into spreading two of the ball bearings apart & sideways pressure on the bearing housing & cage.
Maybe the squealings from a ripped up bearing cage? Or the gears grinding at each other.

I know from practice that if a wheel bearings starting to go bad, do a looooonnnngggg turn to the right, or left, while travelling strait. That puts pressure on the bearings & makes them louder.
Also, running the bad bearings wheel on a continous painted line on the road will quieten it down a bit. Painted road is smoother.

The front differential is sorta like a rear diff. There's a fill plug on it somewhere. With a rear diff you just pop the cover off to drain, but the front ones I'm not sure how alike they are(mine has to be pulled, or you can use a pump to pull the oil out thru the fill hole)

The transfer case should have a drain, and a fill plug.
Do you have a repair manual for that vehicle ?