Trasmission requires 3500 rpm to shift at cetain times

1995 LHS Starts, runs shifts smooth all normal. Engine temperature comes up to normal and all continues to funtion normally. When car sits with engine off raising temp. of engine and is started transmission does not shift until approx. 3500 rpm all grears and rough downshifts. When left for period of time to lower coolant temp. all runs smooth. All vacuum lines ok new plugs, plug wires, and throttle position sensor. No codes are present after ignition key test.