[Jsreo]

Changed mine before each track day per the owners manual

[N Camarolina]

I am nearly certain the owner's manual (including the high performance guide) does NOT tell you to change the diff oil every track event. After the first two changes (see below), it's based instead on number of track hours. I have to check on the exact number but it's something like 20 hrs.

To be fair, they do tell you to change it at 1500 before the first track event, and then (I think) after the first track event. This makes sense since the first 1500 has debris from manufacturing and run-in, and the first track event is likely to be the first time you really place high demands on the rear diff gears and clutch, so likely more unusual wear.

[Buddy Shagmore]

I changed the diff fluid at 5K, put in Mobil 1 syn 75w-90. I have been hearing groaning noises when backing up cold and turning out of my driveway.
I changed it today using AC/Delco Dexron. There was just a fine layer of black sludge on the drain plug. I'm gonna do some slow figure 8's tomorrow morning in a big empty parking lot. Hopefully the groaning will be gone.

[Buddy Shagmore]

Well, I did a few minutes of tight figure 8's this morning. Happy to report no more groans.I guess that and the AC/Delco Dexron fixed it.