hear a "whirring" sound when slowing down in 4 X 4. Anybody know what that is?

its your whole drive system keeping in sync. if i'm right it's not a sound that just start happening. 4x4 is different then AWD. 4x4 locks up so all wheels spin at the same speed. you shouldnt use 4x4 unsless you need to, its made for off road. when its used on dry pavement it grinds the gears out from forcing them to sync

Sounds like a bad wheel bearing, generally when you get drivetrain bind-up the vehicle jerks and the tires will hop, only time you will get that is sharp cornering on dry pavement or when the front and back wheels are different sizes. Four wheel drive mode will put more load on the bearings, could also be a bad front u-joint or front diff.

usely when you hear a whinning noise and go.s away when you make a right turn check your tires or can come from rearend check lube in your pumpkins in otherwards if have a 4wheel drive your differentals