Dodge 2001 Ram 1500 Owner's Manual page 2425

21 - 790 AUTOMATIC TRANSMISSION - 47RE
VALVE BODY (Continued)
The governor plug serves a dual purpose:
• It allows the shift valves to move either left or
right, allowing both upshifts and downshifts.
• When in a manual selection position, it will be
hydraulically "blocked" into position so no upshift can
occur.
The physical blocking of the upshift while in the
manual "1" position is accomplished by the directing
of line pressure between both lands of the governor
plug. The line pressure reacts against the larger land
of the plug, pushing the plug back against the end
plate overcoming governor pressure. With the combi-
nation of the line pressure and spring pressure, the
valve cannot move, preventing any upshift.
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. 252):
• 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 posi-
tion and the transmission is in the first or second
gear range, 1-2 shift control or "modulated throttle
pressure" is supplied to the middle of the accumula-
tor piston by the 1-2 shift control valve. During the
1-2 upshift, this pressure is used to control the kick-
down servo apply pressure that is needed to apply
the kickdown and accumulator pistons. Thus, the 1-2
shift point is "cushioned" and the quality is
improved. During a WOT kickdown, kickdown pres-
sure 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, add-
ing to the spring load on the valve. The result of this
increased "modulated" throttle pressure is a firmer
WOT upshift.
Fig. 251 1-2 Shift Valve-After Shift
2-3 SHIFT VALVE
The 2-3 shift valve mechanism (Fig. 253) consists
of the 2-3 shift valve, governor plug and spring, and
a throttle plug. After the 1-2 shift valve has com-
pleted 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 vehicle speed increases, governor pressure
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 pressure 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 moving it to the right. The
shift valve causes land #4 to close the passage sup-
plying throttle pressure to the 2-3 shift valve. With-
out throttle pressure present in the circuit 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.
BR/BE