Help identifying odd noise

[jalfonso1]

Hey guys,

Recently I have noticed an intermittent noise coming from underneath my Jeep towards the rear. It's not consistent at all, but it does seem to appear after driving for any number of minutes.

I would describe the sound as if I was dragging something on the road. (was the 1st thing I checked for and I'm definitely not Sounds kinda like a type of plastic jug dragging along the road. Sound does not increase or decrease in any gear, including neutral, or when applying brakes or emergency brake. Additionally the sound doesn't change with speed and will appear at random times and go away as well at random.

I first noticed it after driving up a long hill for about 10 mins, when I got to a flat section I heard it for a few seconds then it went away. Now, the last 2 times I have used it it has appeared (and disappeared) at some point during the 30-40 min. trip.

I'm not able to replicate the sound by jacking up the wheels and shifting through all 3 gears or by turning the driveshaft or tires by hand. While I had it on the jack, I removed the tires and drums and nothing is out of place, broken, rubbing or worn. There's about 75% of the pad still left on the shoes.

My first thought was bad wheel bearing in the rear (front has all new bearings, carriers and everything is greased up. Does this sound symptomatic of bad bearings?

Any other common areas I can look for that would produce this type of noise?

I feel like I have checked pretty thoroughly w/o opening anything up. Most recent work I did, over the weekend was changing the Transfer Case rear output oil seal & felt and cleaned and adjusted the brake there. There's no noise or drag there and it is very silent in that area. I actually heard the noise once before I even worked on that.

 

[Torxhead]

I would first suggest checking the diff fluid level and maybe changing it, possibly to a heavier weight gear oil. When you remove the diff cover check the wear on the gears. It could be the wheel bearings, check for any leaking inside on the rear brake backing plate and check for any axle wobbling.

 

[jalfonso1]

Thanks for the suggestions.

Diff oil is good and clean, changed less than a year ago. All looked good at that point and I just checked level recently and oil is a good color and filled to the top with 80/90.

I do have some movement at the wheels, but honestly it's no worse than when I first bought the Jeep around 5 years ago. Just a few millimeters would be my guess. Also, I have no leakage around the drum area.

 

[hagar]

While driving at the speed the noise is heard, you might be able to verify which side might be bad by turning the steering wheel back and forth and putting more weight on one side of the vehicle or the other at a time.
The noise could get louder with more weight or quieter as weight is taken off the offending bearing.

 

[Torxhead]

Another oil option which is for use in heavy duty applications would be to use a 80w-140 gear oil. I have heard of guys using STP as a last ditch effort to quiet things down that is mixed in with existing gear oil.