Dodge 2001 Ram 1500 Owner's Manual page 1909

21 - 274 AUTOMATIC TRANSMISSION - 42RE
VALVE BODY (Continued)
1-2 SHIFT CONTROL VALVE
It contains a valve with four lands and a spring. It
is used as both a "relay" and "balanced" valve.
The valve has two specific operations (Fig. 257):
• Aid in quality of the 1-2 upshift.
• Aid in the quality and timing of the 3-2 kick-
down ranges.
When the manual valve is set to the DRIVE position
and the transmission is in the first or second gear range,
1-2 shift control or "modulated throttle pressure" is sup-
plied to the middle of the accumulator piston by the 1-2
shift control valve. During the 1-2 upshift, this pressure
is used to control the kickdown servo apply pressure that
is needed to apply the kickdown and accumulator pis-
tons. Thus, the 1-2 shift point is "cushioned" and the
quality is improved. During a WOT kickdown, kickdown
pressure is applied between the kickdown valve and the
1-2 shift control valve. This additional pressure is
directed to the 1-2 shift control's spring cavity, adding to
the spring load on the valve. The result of this increased
"modulated" throttle pressure is a firmer WOT upshift.
2-3 SHIFT VALVE
The 2-3 shift valve mechanism (Fig. 258) consists of
the 2-3 shift valve, governor plug and spring, and a
throttle plug. After the 1-2 shift valve has completed its
operation and applied the front band, line pressure is
directed to the 2-3 shift valve through the connecting
passages from the 1-2 shift valve. The line pressure will
then dead–end at land #2 until the 2-3 valve is ready to
make its shift. Now that the vehicle is in motion and
under acceleration, there is throttle pressure being
applied to the spring side of the valve and between
lands #3 and #4.
As
increases proportionately, until it becomes great enough
to overcome the combined throttle and spring pressure
on the right side of the valve. Since the throttle pres-
sure end of the 2-3 shift valve is larger in diameter than
the 1-2 shift valve, the 2-3 shift will always happen at a
greater speed than the 1-2 shift. When this happens,
the governor plug is forced against the shift valve mov-
ing it to the right. The shift valve causes land #4 to
close the passage supplying throttle pressure to the 2-3
shift valve. Without throttle pressure present in the cir-
cuit now, the governor plug will push the valve over far
enough to bottom the valve in its bore. This allows land
#2 to direct line pressure to the front clutch.
After the shift (Fig. 259), line pressure is directed
to the land between the shift valve and the governor
plug, and to the release side of the kickdown servo.
This releases the front band and applies the front
clutch, shifting into third gear or direct drive. The
rear clutch remains applied, as it has been in the
other gears. During a manual "1" or manual "2" gear
selection, line pressure is sent between the two lands
of the 2-3 governor plug. This line pressure at the
governor plug locks the shift valve into the second
gear position, preventing an upshift into direct drive.
The theory for the blocking of the valve is the same
as that of the 1-2 shift valve.
Fig. 257 1-2 Shift Control Valve
vehicle speed increases,
BR/BE
governor pressure