Noise when in 4wd

[heavychevy02]

I just resently bought a 2002 chev silverado selective 4x4 and have noticed a fairly loud growl or whine coming from the front diff when in either auto 4wd or 4 hi worst around 80 km/h gets loud as i accelorate and changes tone when the truck slows down but no noise in 2wd wondering if this is normal or if i am looking at a rebuild on my front diff. thanks for any input.

[04sierracrewcab]

is there a good amount of good gear oil in the diff?

is a service 4wd light on?

[MrShorty]

I just resently bought a 2002 chev silverado selective 4x4 and have noticed a fairly loud growl or whine coming from the front diff when in either auto 4wd or 4 hi worst around 80 km/h gets loud as i accelorate and changes tone when the truck slows down but no noise in 2wd wondering if this is normal or if i am looking at a rebuild on my front diff. thanks for any input.
A little bit of extra noise in 4A/4H could be normal. Excessive noise could be caused by numerous things. My first thought would be front driveshaft u-joints, but it could be a pinion bearing or something in the diff, too. I would probably start by climbing underneath and checking the u-joints, and rotating the driveshaft by hand to see if I could hear/feel where the noise is coming from.

[heavychevy02]

no light on and i just resently changed the oil and they were full before servicing and there was no unusual amount of filings, transfer case is full, u joints feel fine, maybe a pinion bearing thanks for the feedback.

[CoolAirVw]

I'm too lazy to google. How fast is 80Km per hour anyway?

[CamoRig]

80 kph is about 50 MPH, not sure I ever needed 4wd at those speeds but I never did any kind of racing just need it to keep me from getting stuck in mud holes now and back when I needed to climb mountain trails in Alaska.