I posted pretty much the same thread on Sunday in the autocross section and haven't gotten any responses so I'll try here,

Got a LS 5 speed, did what's probably my 12th or 13th autocross event on Sunday, car was getting hot so I opened the hood to cool down after a couple runs and found my trans had started belching fluid out of the vent on top of the trans. I'm sure it's from the amount of time I spend full throttle and the amount of wheel spin I have. My questions 1)will buying stickier tire that I have less a chance to break free work? Or should I spend the time and money to find LSD?
2) I know I have to flush the fluid, what does everyone put in? Stock? Full synthetic? Or something else?

 

Use stock fluid back in the trans, I believe the F23 uses something similar to ATF, but don't quote me on that.

Consider adding a temp gauge to the trans, it's easy to do via the drain plug. This will give you an idea of how bad it's overheating, then you can try stickier tires and see if it changes enough to help. If not, you may need an LSD but I would almost say to add a cooler for less than the cost of an LSD and install.