New wheels with different offset may help you. Puts the load back where it was intended to be from the factory. I'm going to venture a guess and say that your wheels are sticking outside of your rig a ways? This usually will put extra stress on the wheel bearings.
Also found this with a quick search..
"Wheel Bearings
I have found that when running large tires on the Explorer a severe jolt to the wheel can cause the outer spindle locknut to come loose, causing excessive play in the wheel bearing (loss of preload).
In the stock configuration, the inner spindle nut has a pin which engages a keyed washer. The keyed washer keeps the inner nut from turning but there is nothing to keep the outer nut from breaking loose except the torque that is applied to it.
Warn now has a solution to this problem. Warn part #37207* (conversion kit) replaces the stock keyed washer with a new washer which incorporates slots instead of holes for locking purposes. The new outer locknut has been drilled for three small allen screws. These screws when tightened will engage one or more of the slots in the washer. Combined with the stock pinned inner locknut this makes for a nearly bullet proof set up. I have yet to experience a problem with the new locknuts.
*Warn has discontinued part #37207. The only way to get the required parts is to make them yourself."