2004 Explorer roaring noise

[Lee082m]

My explorer is rear wheel drive. It makes a roaring noise while driving. It doesn't change moving left to right or letting off the gas. If the wheels are turning, it's roaring. At first I thought it was coming from the front so I had both front wheel bearings changed. However, now I know it's coming from the rear. I jacked up the truck and checked both rear wheels for play or give. They do not move. They are good and tight. So it's not the rear hubs. I let a mechanic drive it and he says it needs a disc bearing kit. There are bearings that are on each side of the rear axles and because it would all have to be torn apart to get to them labor would cost about 400 bucks plus the cost of the kit. I've been looking to sell and have already spent quite a bit on it and don't want to spend much if any more. Has anyone heard of this? Does this sound correct? Please help.

 

[IPcamper]

The 02 and 03 years are know for rear differential problems, with a roaring sound being common. If you search through this forum you can find a lot of information about the differential that might help. As for the axle bearings in the differential, they can fail, and the noise would be related to the wheel speed. The gears can wear and cause a roaring sound as well.
When was the fluid in the differential changed? If it is the gears and the wear isn't too bad, you can sometimes buy some time by changing the fluid and using a high quality fluid like Royal Purple. But that won't help if the wear is bad, or if the bearings are failing. Replacing the axle bearings is a fair amount of labor, I am sure the shops around me would charge a lot more the $400.

As for the rear wheel bearings, just because they feel tight, they can still be the cause of the noise. You can jack the vehicle up and put it in neutral so you can spin the wheels easily, listen and feel for any slight sound, or hesitation / binding in the rotation. if necessary, do it with the brakes removed to eliminate any drag from a worn / warped rotor.

My 03 had the rear differential fail at 90,000 miles and it was rebuild by the dealer. The right axle bearing, pinion bearing went bad and the pinion gear was worn. Last fall the differential started to fail again with 226K miles on it. The pinion bearing, and who knows what else, but it sounded like a Lear jet at 40mph and was spitting metal flakes into the fluid. Just before I replaced it, the pinion seal started leaking. Since this was the second time it failed, I figured it was one of the bad differentials from '03. For my Christmas project, I replaced it with a used differential from a 04 Mountaineer with 139K miles. While the differential was the worst of the problem, it turns out the wheel bearings were going bad as well, so I replaced them while I had it apart. So far everything is good.

 

[dkl]

The rear wheel bearings will start to fail long before you are able to detect any free play. The noise they make, resonating through the (sheet metal) disc brake dust shield sounds like studded snow tires on spring slush. It's a loud drone that only gets worse the faster you go.

Try putting it up on a rack and using the right tools to verify the problem is with the differential/axle bearings. I think it's sometimes difficult to identify with a road test, the Mechanic I first went to suggested new tires.