I've had the rear differential/pinion gears replaced 3 times, but the loud whine from the grinding rear-end gears continues to return after a few thousand miles. I was finally told that this is normal, and wouldn't pose a problem, but the grinding noise has now gotten too loud to drown out with the radio. My research into this problem has led me to discover it's a very common problem due to Ford's design flaw (the soft aluminum housing expands at a different rate than metal gear assembly). I've also learned the rear end will eventually seize; just pray it's not on the expressway with your children on board. After 1yr/12000 miles, you're stuck paying >1.5K for another temporary fix. Too bad enforcement of consumer protection was gutted in 2001, as the well-known rear-end design problem of these vehicles has gone unchecked. Ford should be forced to recall these vehicles, since it is a safety issue when the rear-end seizes up eventually.
Ford should stand behind their decision to "cheap out" on the rear differential assembly, before enough disgusted owners initiate a move to educate all 2002-up Explorer owners of the true origin of this infamous problem (Google "Explorer Rear end whine") and move forward with a class-action lawsuit.
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