2010 5.7L 1500, humming/rubbing when coasting in rear.

[new2trucks]

Recently noticed a humming or rubbing sound when I let off the gas, takes a second or two then its audible. First thought is wheel bearing but that doesn't make sense because I'm not accelerating. I'm new to trucks and 4WD so I'm trying to learn as much as I can. What other possibilities or has someone has the same issue?

EDIT: noise goes away when in Neutral.

 

[Burla]

Jack up rear end and see if wheels spin easily with trans in neutral and parking brake off, yes you will need to be level to do this.

Humming could be considered whining which would be gears, get a top diff fluid and change immediately. Valvoline now has bags, get 75w140 x 3 bags and do it asap. Anyone can do this, nothing to it. Most gear oils you will need a pump, the newer bags you need nothing but a wrench.

If you have a temperature gun it would be helpful to see if there is any white hot parts after your trip.

There are other things as well, post a youtube of the sound if you can.

 

[new2trucks]

Thanks Burla, also wanted to mention noise goes away when the truck is in Neutral.

 

[Burla]

So it is in the driveline somewhere, good time to check diff fluid anyhow. If it goes away in neutral you can most likely rule out brake issue and no need to jack up.

 

[Racer9]

Is your truck an extended cab long wheelbase? That could be carrier bearing, assuming it has one.
Also check the u-joints over real good.
Other thing is pinion bearing, see if there's any up and down or side to side movement in the rear yoke.

 

[new2trucks]

Racer9,

No mine is a Crew Laramie 4WD.