Dodge Durango (DN). Manual — part 80

Fig. 31 1–2 Shift Control Valve

Fig. 32 2–3 Shift Valve-Before Shift

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DESCRIPTION AND OPERATION (Continued)

After the shift (Fig. 33), 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.

3–4 SHIFT VALVE

The PCM energizes the overdrive solenoid during

the 3-4 upshift (Fig. 34). This causes the solenoid
check ball to close the vent port allowing line pres-
sure from the 2-3 shift valve to act directly on the 3-4
upshift valve. Line pressure on the 3-4 shift valve
overcomes valve spring pressure moving the valve to
the upshift position (Fig. 35). This action exposes the
feed passages to the 3-4 timing valve, 3-4 quick fill
valve, 3-4 accumulator, and ultimately to the over-
drive piston.

3–4 TIMING VALVE

The 3-4 timing valve is moved by line pressure

coming through the 3-4 shift valve (Fig. 36). The tim-
ing valve holds the 2-3 shift valve in an upshift posi-

tion. The purpose is to prevent the 2-3 valve from up
or downshifting before the 3-4 valve (Fig. 37).

Fig. 33 2–3 Shift Valve-After Shift

Fig. 34 3–4 Shift Valve Before Shift

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DESCRIPTION AND OPERATION (Continued)

3–4 QUICK FILL VALVE

The 3-4 quick fill valve provides faster engagement of

the overdrive clutch during 3-4 upshifts. The valve tem-
porarily bypasses the clutch piston feed orifice at the
start of a 3-4 upshift (Fig. 39). This exposes a larger
passage into the piston retainer resulting in a much
faster clutch fill and apply sequence. The quick fill
valve does not bypass the regular clutch feed orifice
throughout the 3-4 upshift. Instead, once a predeter-
mined pressure develops within the clutch, the valve
closes the bypass. Clutch fill is then completed through
the regular feed orifice.

THROTTLE VALVE

In all gear positions the throttle valve (Fig. 40) is

being supplied with line pressure. The throttle valve
meters and reduces the line pressure that now
becomes throttle pressure. The throttle valve is
moved by a spring and the kickdown valve, which is
mechanically connected to the throttle. The larger
the throttle opening, the higher the throttle pressure
(to a maximum of line pressure). The smaller the
throttle opening, the lower the throttle pressure (to a
minimum of zero at idle). As engine speed increases,
the increase in pump speed increases pump output.
The increase in pressure and volume must be regu-
lated to maintain the balance within the transmis-
sion. To do this, throttle pressure is routed to the

Fig. 35 3–4 Shift Valve After Shift

Fig. 36 3–4 Timing Valve Allowing 4–3 Shift

Fig. 37 3–4 Timing Valve Allowing 3–2 Shift

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DESCRIPTION AND OPERATION (Continued)

reaction area on the right side of the throttle pres-
sure plug (in the regulator valve).

Fig. 38 3–4 Quick Fill Valve Before Shift

Fig. 39 3–4 Quick Fill Valve After Shift

Fig. 40 Throttle Valve

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DESCRIPTION AND OPERATION (Continued)