Detent Downshift Valves In Second Gear Position

At vehicle speeds below about 70 mph, a forced or detent 3-2 downshift is possible by depressing the accelerator pedal fully. This will position the throttle valve (T.V.) plunger to allow T.V. oil to enter the detent passage. This oil, called detent oil, is routed to the line bias valve to boost M.T.V. pressure. M.T.V. oil acting on the T.V. boost valve will boost line pressure about 10 psi. Detent oil also flows to the 2-3 throttle valve, where detent and M.T.V. down oil acting on separate areas of the 2-3 throttle valve will close the 2-3 shift valve against governor oil and permit 3rd clutch and accumulator oil to pass through an orifice and exhaust at the 2-3 shift valve.

At vehicle speeds above approximately 50 mph, governor oil will act to close the 3-2 control valve. Now the exhausting 3rd clutch accumulator oil from the intermediate servo seats the 3rd clutch accumulator check ball and flows through another orifice controlling the intermediate band apply. This results in a smooth 3-2 shift at high speed.

A detent 2-1 downshift is possible at speeds below approximately 30 mph because detent oil pressure, in combination with 1-2 spring force, acts on the 1-2 throttle valve to close the 1-2 shift valve, resulting in the transmission shifting into first gear.

Those model transmissions with no part throttle 4-3 downshift will have a detent 4-3 or 4-2, in addition to detent 3-2 and 2-1 downshifts.