Well, not today, but last month, I replaced the rear differential in my 03 Explorer. The original 3.73LS diff died a horrible bearing failure at 90,000 miles and the dealer rebuilt it under an extended warranty. Well at 225,000 mile, it sounded like a lear jet at 40 mph and the oil was full of metal. I thought seriously of rebuilding it again, but since it failed twice, I was wondering if it had a warp housing or a mis-shaped bearing seat in the housing, so I picked a used 3.73LS with 139,000miles off of 2004 Mountaineer from LKQ ( with a 6 month warranty ). Changed out the seals on the replacement with new ones. I ran into a hic-up on removing the old one, the left axle would not come out. I hit the thing with a piece of wood and a mallet, nothing. I used a crow bar to pry it out ( I wasn't keeping the old diff anyways. ) could not budge it. I ended up separating the inner CV and leaving part of it in the diff. While I was at it, I found that the right rear wheel bearing was bad, and the left was only slightly better. So, I pressed in new bearings. I picked up a new left axle and put it all back together. A long weekend for me. I spend a little less than $600 for the replacement differential, new bearings, new axle, axle nuts, and fluid. I am sure the local shops around here would have charged me 3 to 4 times that.
It is running smooth and quiet. If I can get a few years out of this differential it will be great!
A note for those who might press their own rear bearings, the 12-Ton Harbor Freight press is barely able to do the job. I had to put the bearings under full pressure, then heat the knuckle with a torch to ~200 degrees and use a hand sledge to tap around the press plate to get the bearing to start moving. Once it started to move the press could handle it, but it wasn't enough to break the bearing free by itself. The 12-Ton press is more than enough for installing the new bearings, but other's have mentioned needing a 20-Ton press for this Job and I can see why.