chevy th350 problems

ok...it shifts through the gears fine till i hit 55mph..at that point it shifts down to 1st or 2nd gear but it's like it's in neutral...checked and replaced modulator and line...adjusted, then threw out tv cable and installed a plug...still the same problem... it has a b&m 2000 stall converter, and a b&m shift kit....worked great in the previous car...sat in my garage for a year...now it's doin this...any help or suggestions would be greatly appreciated..thanks

and if i have it past 1/4 throttle on take off...it never comes outta first gear...

no one has any ideas?:CRY: i cant think of anything except swapping the tranny out, and i REALLY dont wanna do that...:HMMM: