'02 XLT 3.73 LS differential howl

I purchased my '02 Explorer XLT w/tow package new in May of 2001.
Fourteen months ago (just before the warranty expired), I took it to my
servicing Ford dealer to have them check the differential for a whining
or howl noise. They determined that it needed new ring and pinion
gears so they ordered the parts and replaced them a week or so later.
All was well for the first 1000 miles or so and then the noise started
to gradually return. As before, the noise was most noticeable between
approximately 55 and 63 MPH.

We went through a period of time after that where we seldom drove on
the freeway, until going on a 3400 mile vacation earlier this month. I
was towing my tent trailer and had to drive right in the 55 to 60+ MPH
area. As the trip wore on, the howling noise seemed to increase. When
we returned home I took my Explorer back to my servicing dealer for
diagnosis and sure enough, the verdict was that it needs another new
ring and pinion. Although the ring and pinion replaced under warranty
only had 9000 miles on it, the 12 month/12,000 mile warranty on the
warranty repair had expired by a little less than 2 months. So, I was
told that the repair cost would be $1100.00. I complained and the
servicer agreed to give me a 25% discount.

Disgusted, I called FoMoCo and got basically the same answer: sorry,
the 12/12 warranty on the replacement ring and pinion has expired. You
have no warranty and therefore, you must pay for the new replacement
parts.

To add insult to injury, Ford could not come up with any TSB's or
recalls on the 3.73 LS differential and could not assure me that the
replacement parts were any better than the two sets that have already
failed.

So, I'm very, very disappointed with Ford at this point. 9000 miles on
a differential just doesn't cut it, not to mention my Explorer only has
40,000 miles total. I think I'm going to have it fixed and then trade
it in on some other brand of SUV, such as a Honda or Acura.

4.0L