havent been able to determine if S550’s without the oem diff sensor have a calculated temp that triggers an over temp warning? Headed out for my first track day soon and wondering if I’ll get a warning or just have to assume I’m cooking my diff.
My '15 doesn't have a diff sensor either and there is no warning or limp mode that I have experienced. I'm using thermax temperature stickers on the diff to monitor it. They are rectangular blue stickers with a white strip in the middle, 241* being the bottom of the white strip and 309* being the top. The white strip turns black as it reaches each temperature level so you can "read it" quickly by looking under the car and seeing how much white strip has turned black instead of getting close and trying to read the numbers. I don't recall ever seeing a sticker read above 290*; 3:31 t-lok not torsen.
Wrapping the exhaust made a big difference for me, haven't had an axle overheat warning since I did that and I was getting them regularly before then, on a hot day I could barely get 20 minutes in. That plus I have a small battery powered fan I aim at the diff between sessions.
The 75w140 fluid and wrapping the exhaust around the diff seemed to have only bought me an extra lap or two last year. They definitely do help, however the only real way to solve this issue is a diff cooler.
If you're headed out for your first time on track, I wouldn't worry too much about it and just send it. Focus on your driving skills. If the warning does come up on your dash, give the car a cool-down lap and bring it in. It usually takes around 20 min for the warning light to come up for me.