I decided to change out my fluid today, since my unit was at a charity golf tournament, and I can't golf anymore... . so I had the day off.
I went to AutoZone, but they only sell the Pennzoil Syncromesh two quarts at a time... what a waste of time, but I was able to buy a 17mm hex head socket, so not a total loss.
Then I went to O'Reilly Auto Parts and asked them if they sold Pennzoil 3501, and they looked at me funny. After asking me what truck, they looked at the new Pennzoil catalog and it says "GLS" (not a typo)... finally after about ten minutes on hold with Pennzoil, the tech guy tells my parts guy it's Syncromesh... . he looks at me and says, "It's Syncromesh!", to which I replied, "Yeah, maybe I should have said that in the first place"... . I felt pretty dumb, but the parts guy is a friend, so all was cool. I bought seven quarts.
Got home and did some chores, let the transmission cool down and then went out and drained it... . fluid was still amber... . I had it rebuilt at 95,000 miles and I'm now at 124,000..... so 29,000 miles on the rebuild, with lots of towing... . not bad. No metal particles at all.
I found out real quick that the fill port wasn't going to cut it, when it started overflowing at 3 quarts, so I went in from the top and filled it up. I also added a bottle of Mopar LSD... I found that it works really well.
We'll see how 7 quarts fares, vs the recommended 4. 75 quarts... . I'm sure Blumenthal knows their business.
Definitely a worth-while DIY job.