904 Transmission issues.

I have a 904 transmission behind a 410 sb.I had the tranny redone for racing with new belts,lower first gear,change drum and a TransGo-3 manual valvebody kit.My t.c is a Coan 8 inch 4500 stall.I,ve had the car out for a test drive around the block(2 miles)and everything was good,so I trailered the car to an alignment shop for alignment.After the alignment I went for another test drive to check the alignment(alls good)I turned a corner and poof no gears whatsoever(no 1st,2nd,3rd or reverse,just park)I,m gonna pop a line off to see if the pump is pumping?I was also told to put a spring on the kickdown lever at tranny at 3/4 open for pressure.I,m hopeing it,s just the pump,cause everything was all good.Any ideas what might have gone wrong?Any help will be appreaciated.Thanks

P.S All internals were installed by a very recommended tranny builder for racing.