Highway speed whining

[Ryan2828]

2017 silverado 5.3 with 3.42 rear end. Noticed when its cold out a get a rythmic type whining that comes and goes about every 5 seconds. At highway speeds it more consistent. If i hear it and put it in 4wd Auto it immediately goes away and doesnt return after i go back to 2wd.  It doesn’t do it if its above 45 degrees outside or i drive the truck for a distance. I’m trying to get as much info as i can before i take it in because the truck has aggressive tires and i know i’m going to get the classic “its your tires” response from the dealership. Any info is greatly appreciated 

[2017_whitez71]

Cold tires?  Are the tires at proper pressures?  If they are under inflated they will make more noise.

[Ryan2828]

Its not the tires

[hirdlej]

Does it go away with any positive or negative throttle?  Just noise at steady cruise?  If so it's probably your rear differential.  I went through 4 of them in my '15 before they finally got it right.

[Ryan2828]

Throttle position doesn’t affect it.  It does change with speed. Above 75 its very hard to hear because of wind and tire noise

[Ryan2828]

Going into 4wd auto immediately does away with the noise