Rumble noise at highway speed

[A.J.C.]

I need some direction to what could be causing a low rumble at highway speed. It sounds like a subwoofer making a low bass rumble tone at 70mph or higher. When coasting, it gets quieter. When accelerating, it gets louder. Also, at low speed acceleration during tight turns, the axle shudders like it his a "locked" differential. It has the limited slip with the friction modifier additive.

There also seems to be slop between the transmission and rear axle. When I'm coasting and give quick acceleration, it clunks.

I have replaced all the u-joints in the drive shaft.

My explorer is a 5.0 V8 2WD.

Any help is appreciated but I'm thinking it needs a new rear axle. The transmission output shaft can be wiggled slightly but it is not leaking.

 

[shadowless127]

Bad wheel bearing, bad alignment, or possibly a d-shaft out of balance.

 

[masospaghetti]

Bad rear axle bearings or worn axles will cause this. Bad differential carrier bearings will also cause it, and both sound almost the same. Low frequency rumble at high speed. A bad differential pinion bearings makes a higher pitch noise since its spinning at 3.27-3.73x as fast as the carrier and axle bearings.

You could find a used diff, but it might make more sense to get yours rebuilt with new bearings. A local 4x4 shop did mine for about $450. Although you could take your chances and replace the axle bearings first to see if that solves your problem, its much cheaper than rebuilding the differential. You can get axle repair bearings that will work even if the axle itself is worn and they are not expensive.

 

[92eddie4x4]

To hit on your "locking" differential. I would suggest searching on the viscous coupler in the transfer case. I've had two go bad in two Explorer generations. Also, the chains in the transfer case stretch causing a buck upon acceleration from a stop.