Hydraulic System--Intermediate-Range Operation

exhaust port, coupled with the limited flow caused

throttle valve (TV) pressure is connected to the

by the restriction in the feed line, causes a reduced

throttle (T) pressure circuit. From this point, and

pressure in the inhibitor circuit. This reduced

t h r o u g h o u t the remaining throttle opening

pressure is calibrated against the downward force

movement, TV and T pressures are equal. Both

required to downshift the low-intermediate shift

increase as the throttle is opened. Throttle (T)

valve at a specific vehicle speed (and specific G2

pressure is directed to the upper surface areas of the

low-intermediate shift valve, intermediate-high

pressure).

shift valve, and the lockup valve.

(3) In the high-intermediate inhibitor circuit,

hydraulic action is identical to that described in (2)

(2) At the low-intermediate shift valve, T

above, except that calibration of the pressure is to

pressure is exerted downward on the shift valve and

that required to downshift the intermediate-high

upward on the blocker plug. This pressure tends to

shift valve.

hold the shift valve downward against the low-

intermediate shift plug which is being pushed

(4) In low range, oil escapes continuously at

the exhaust ports in the inhibitor bores.

upward by G2 pressure. Thus, throttle opening

i. Lockup Clutch Circuit (blue, white--fig. 2-4).

delays upshifting. The greater throttle opening is,

When the lockup valve is upward, main pressure

the greater is upshift delay.

supplies the lockup feed line. When the flow valve

(3) At the intermediate-high shift valve, the

is upward, pressure in the lockup feed line supplies

effect of T pressure is identical to that described in

oil to the lockup clutch circuit. Lockup pressure

(2) above. However, the transmission speed range

applies the lockup clutch.

( a n d G2 pressure range) within which the

movement of each of the shift values occurs is

2-16. Hydraulic System--Intermediate-Range

different. This difference is caused by the difference

Operation

in spring loads and plug areas against which G2

a. Main Pressure Circuit (red--fig. 2-5).

pressure works. Thus, the low-intermediate shift

(1) The main pressure circuit in intermediate

valve, working with the lighter spring and greater

range functions as described in paragraph 2-15a

plug area, will upshift at a lower vehicle speed (and

for low-range operation except for the differences

G2 pressure) than will the intermediate-high shift

outlined in (a) through (e) below.

valve.

(a) Main pressure is cut off from the passage

(4) At the lockup valve, T pressure delays the

(line 2) leading to the intermediate-low inhibitor

upward movement of the lockup valve and thus

circuit.

delays lockup. The delay varies with throttle

(b) Main pressure is extended from the low-

opening. Should the throttle be closed completely

intermediate shift valve bore to the intermediate-

while the transmission is in low range, there would

high shift valve bore.

be no T pressure or TV pressure to inhibit the

(c) Because a clutch (intermediate range) is

upward movement of the lockup valve.

in the initial stage of being charged, there is a rapid

(5) Throttle (TP) pressure can cause a

flow of oil through the orifice at the left side of the

downshift at full throttle under certain conditions

flow valve. This reduces the pressure downstream

as well as preventing an upshift under some con-

of the orifice and causes the flow valve to move

ditions. T pressure can also cause a change from

downward.

lockup operation to converter operation by moving

(d) The downward position of the flow valve

the lockup valve downward. Input and output

temporarily releases lockup clutch pressure. In

speed and governor (G1 and G2) pressures in-

addition, main pressure is cut off from the line

fluence the point at which upshifts, downshifts, or

leading to the area above the extender valve ball.

lockup occur when the throttle is manipulated.

This permits pressure above the trimmer plug to

h. Inhibitor Pressure Circuit (dotted red--fig. 2-

escape past the extender valve ball and to exhaust

4).

finally through the same port at the right of the flow

(1) In low-range operation, the intermediate-

valve bore through which lockup pressure exhausts.

low and high-intermediate inhibitor circuits are

(e) Release of pressure above the trimmer

charged. The only function of these pressures in

plug permits the trimmer plug to move upward.

low-range operation is to prevent the upshifting of

This, in turn, permits the trimmer valve to move

either shift valve.

upward until main pressure escapes at the exhaust

(2) In the intermediate-low inhibitor circuit,

port at the left of the trimmer valve bore.

oil enters (from main) through an orifice and exerts

(2) The results of the differences in the main

pressure against the upper surface areas of the

pressure circuit are explained in the various circuit

inhibitor valve and the blocker plug. The inhibitor

explanations which follow.

valve moves downward against its spring and

b. Converter-In Circuit (yellow--fig. 2-5). The

allows oil to escape from the exhaust port at the left

converter-in circuit functions as described in

side of the valve bore. The escape of oil at the

paragraph 2-15b.

2-14