my 1992 celica gts wnt shift till u red line it...whats wrong

Could be a cracked or leaking vacuum hose going to the vacuum modulator on the tranny or could be a problem with the trans itself (ie.. valve body sticking, vacuum modulator itself). Did this start happening suddenly? or intermitantly? Also, could be broken, sticking or misadjusted T/V cable (kickdown cable). Hard to say without physically seeing the vehicle, but those are the most likely causes IMO