1956 AMC Hudson Technical Service Manual Supplement

FOURTH SPEED 4-3 DETENT DOWNSHIFT
52
It may be desirable to downshift the transmission from fourth to third
speed at a speed higher than the part throttle downshift would occur.
This downshift can be made up to speeds of approximately 65-70
As the throttle lever contacts the detent valve, the increased
resistance is to warn the driver and prevent an accidental downshift.
If additional foot pressure is used, the detent valve moves to the right.
Detent oil is then directed to the 3-4 shift valve which will close the
valve against governor pressures and the transmission will downshift
from fourth to third gear.
When the detent valve moves to the right, it cuts off the main line
passage through the 3-4 governor valve to the pressure regulator valve.
Pump pressure immediately builds up to a maximum operating
pressure for the fourth to third gear downshift.
M.P.H. by pressing the accelerator pedal all the way down.