I currently have a TCI streetfighter C4 in my 66 mustang behind a 300hp 302. I was getting on the freeway last night hit second gear just fine, revved up to about 5000rpm then hit 3rd, only to hear a loud clunk noise and lose all my gears. It'll hold park, but any other gear feels like neutral, no grabbing or grinding whatsoever. Tranny fluid looks clean, driveshaft and u- joints intact, no leaks. The trans has about 20,000 miles on it and has never given me trouble before. Any ideas about what may have broke?