Well, just for the record, I re-changed my diff oil. After reading my owner's manual, I found that it called for 75W-140. I had also found a few claims that Royal Purple help quiet minor gear whine. Well, it didn't for me, and I chalked up the Mobil 1 75W-90 to an additional fluid flush.

As for the manual trans I changed it out with Royal Purple 5W-20 last weekend. Again, my owner's manual seems to differ from later years. It calls for ATF+4. However, that's not what was in it. Apparently someone had already changed it over to motor oil.

For the DIY'ers, both fluid changes were pretty easy. The diff I did without even jacking up the car. The trans I did on a lift, but only because I already had it up there. However, a second person is pretty much a must.