The higher engine speed and line pressure would
open the vent too far and reduce line pressure too
much. Throttle pressure, which increases with engine
speed (throttle opening), is used to oppose the move-
ment of the pressure valve to help control the meter-
ing passage at the vent. The throttle pressure is
combined with spring pressure to reduce the force of
the throttle pressure plug on the pressure valve. The
larger spring at the right closes the regulator valve
passage and maintains or increases line pressure.
The increased line pressure works against the reac-
tion area of the line pressure plug and the reaction
area left of land #3 simultaneously moves the regu-
lator valve train to the right and controls the meter-
ing passage.
The kickdown valve, along with the throttle valve,
serve to delay upshifts until the correct vehicle and
engine speed have been reached. It also controls
downshifts upon driver demand, or increased engine
load. If these valves were not in place, the shift
points would be at the same speed for all throttle
positions. The kickdown valve is actuated by a cam
connected to the throttle. This is accomplished
through either a linkage or a cable. The cam forces
the kickdown valve toward the throttle valve com-
pressing the spring between them and moving the
throttle valve. As the throttle valve land starts to
uncover its port, line pressure is “metered” out into
the circuits and viewed as throttle pressure. This
increased throttle pressure is metered out into the
circuits it is applied to: the 1–2 and 2–3 shift valves.
When the throttle pressure is high enough, a 3–2
downshift will occur. If the vehicle speed is low
enough, a 2–1 downshift will occur.
SWITCH VALVE
When the transmission is in Drive Second just
before the TCC application occurs (Fig. 41), the pres-
sure regulator valve is supplying torque converter
pressure to the switch valve. The switch valve directs
this pressure through the transmission input shaft,
into the converter, through the converter, back out
between the input shaft and the reaction shaft, and
back up to the switch valve. From the switch valve,
the fluid pressure is directed to the transmission
cooler, and lubrication pressure returns from the
cooler to lubricate different portions of the transmis-
sion.
Once the TCC control valve has moved to the left
(Fig. 42), line pressure is directed to the tip of the
switch valve, forcing the valve to the right. The
switch valve now vents oil from the front of the pis-
ton in the torque converter, and supplies line pres-
sure to the (rear) apply side of the torque converter
piston. This pressure differential causes the piston to
apply against the friction material, cutting off any
further flow of line pressure oil. After the switch
valve is shuttled right allowing line pressure to
engage
the
TCC,
torque
converter
pressure
is
directed past the switch valve into the transmission
cooler and lubrication circuits.
21 - 190
46RE AUTOMATIC TRANSMISSION
DN
DESCRIPTION AND OPERATION (Continued)