When, with engine kept stopped, driven road wheels are turned, the
toroidal type continuously variable transmission is suppressed from
shifting toward a higher speed side. That is, when, with the engine kept
stopped, the road wheels are turned in a reverse direction due to a
traction of a motor vehicle with its front end facing backward, an extra
oil pump driven by the road wheels produces an oil pressure which is
applied to a hydraulic servo mechanism to keep a speed change ratio at a
lower speed side. While, when, with the engine kept stopped, the road
wheels are turned in a forward direction due to a traction of the motor
vehicle with its front end facing forward, the oil pressure produced by
the extra oil pump is not practically used. Under this condition, a
biasing spring suppresses a servo piston from moving in a direction to
bring about a speed change ratio for the higher speed side.