Transmission failure, HELP NEEDED

[1980 malibu]

Last night i was doing a couple test runs on an empty road and as i was in wide open throttle, it shifted from 1st to 2nd, then 2nd to 3rd but 1 second after it shifted in 3rd it acted like it was in neutral and my engine rev'd freely. i thought i really was in neutral but i was in 3rd. now heres the problem, it wont engage in 1,2,D,OD, or reverse at all anymore, but when i put it in park the tranny locks up like normal. I have no idea what happened . i have a rebuilt TCI streetfighter 200r4 capable of handling 450 HP...i'm only runnsing about a little over 300 to the wheels. the rear end isnt broken, the drive shaft is still intact, it has to be something in the tranny. anyone have suggestions? input would be appreciated

 

[turbocaddy1982]

check the fluid cold,should be above level, warm eng, check and if it goes down to full mark the pump is working,if no noise when running...might be the same problem that happened to me, went to pass someone and pop,trans went into neutral, dropped trans and found converter stripped splines in the middle that connects to the input shaft..