ok my rearend just started making a wierd noise today. Out of the blue. I know what gear whine is, and this isn't it. It is somewhat of a whine, though a deep one, not high pitched. Maybe even a grind. But thing is its much more distinguishable at low speeds. Doesn't change when i hit the brakes either. Only thing i can think of that happened was last time i drove it was when it snowed and my driveway was covered in ice, and i was trying to back it into the garage. i would get like halfway and then it would just start spinning. That shouldn't cause a problem though. I took it to my shop today and we got it up on the lift and added more lube in the rear end, and he said the brakes looked fine. So i have no clue what is going on. Also, maybe it is my imagination but lately i have been feeling liek my car has been getting this floating sensation on the highway, where its like very slightly and gently moving laterally, like wiggling almost at speeds of 70+. Again maybe im crazy but I've been noticing it, and it feels really wierd, I thought maybe it was the road, but I'm starting to think it actually might be happening.

 

maybe the wheel bearings have had enough?

 

A friend of mine had an explorer that had about the same problems as you describe.... slight grinding noise that changed pitch with speed and also a fluttering or vibration on the road. Turns out one of his carrier bearings let go and the carrier itself was moving around. Might want to pull the rear cover and check ASAP. He drove it for a couple hundred miles like that, got worse and worse all along, and it ruined his gears (began whining due to the contact patterns being screwed up).

Just a possibility.