Bruce,
Welcome to the slippery slope - pun intended.
Exercising the car on a real race track will cause a series of these kinds of problems. I have melted off the plastic dipstick in my power steering, lost engine
oil through a variety of places such as external plumbing for filter, cooler, valve covers etc., had shocks lose their
oil and many more.
The cause for this leakage is stressing the car's components in ways that are never encountered on the street. Heat builds up and away goes one or more kinds of fluid.
Most kit cars are not constructed with good resistance this kind of usage, so these leaks are going to happen. Even those that are targeted to the track have usually some period where things go awry and need mods to make them work correctly under track duress.
So if you are going to do this kind of activity again, you need to put on your Sherlock Holmes hat and figure out where this leak is, and then come up with a way to correct it.
If it is the differential, try to find out - maybe from Currie? - how to add a leak-resistant vent. It might only take a little baffle to accomplish this.
Be prepared to have other episodes - it's part of the experience
BTW, keep an eye on your
oil pressure in turns, especially if you get a set of track tires which allow cornering at higher Gs....
Tom