Been there - done that... (twice in one race day, actually).
My problem appears to have been a bad bearing or two. After replacing the bearings, and keeping them cleaned, I have not cooked another motor running the same gearing I was running originally. I still have CRAZY hot motors, but I haven't cooked another one ----- yet.
Now I have jinxed myself, and I will probably waste 1 Saturday.
BTW - hidden bearings are important too... Don't just think of the wheel bearings. (I am not familiar with where all the bearings are on the TC3) The worst bearing I had was on the pulley for the belt tension on my Losi.