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.