Abstract: A gas turbine engine and automatic transmission power train having a modulator valve controlled by an engine compressor pressure and altitude responsive force actuator and a speed governor to provide a modulator pressure increasing with increasing engine power during normal engine operation and decreasing with increasing output speed operative to increase friction drive capacity and increase upshift speed with increasing modulator pressure. The force actuator provides a force which increases with increasing compressor discharge pressure and an altitude aneroid provides an opposing force decreasing with increasing altitude so the net actuator apply force increases with increasing compressor discharge pressure and altitude and is the same at the same engine power at all altitudes.