Hydraulic System--Low-Range Operation

downward, with the low-range clutch (e below).

c. Front Governor (Gl) Circuit (blue, b l a c k --

( 6 ) O i l f l o w i n g t o the high-intermediate

fig. 2-3).

inhibitor circuit is restricted by an orifice before it

(1) Pressure or flow in the front governor

reaches the inhibitor valve and the intermediate-

circuit is caused by the front fluid velocity governor

high blocker plug. Refer to paragraph 2-20a for an

( p a r a 2-7). The three branches of the circuit

e x p l a n a t i o n of the high-intermediate inhibitor

connect with the main regulator plug, lockup valve

circuit.

plug, and a ball check valve at the right of the

( 7 ) O i l f l o w i n g t o the intermediate-low

manual selector valve.

inhibitor circuit is restricted by an orifice before it

(2) In neutral (and reverse) the ball check

reaches the inhibitor valve and low-intermediate

valve is always open (downward) because there is

b l o c k e r plug. Refer to paragraph 2-21a for an

no pressure below the ball to seat it (upward). The

o f the intermediate-low inhibitor

explanation

line, below the ball, exhausts around the manual

circuit.

selector valve stem. Thus, there is a flow, but no

(8) At the lockup valve, which is in lockup

pressure in the front governor circuit. As a result,

position (upward), main pressure divides to two

the main regulator plug and lockup valve plug

branches. The lower branch is still blocked as in

remain down. Main pressure is not modulated by

converter operation. The upper branch is open to

front governor pressure, and lockup cannot occur in

l o c k u p feed. Lockup feed also divides to two

neutral operation.

b r a n c h e s . The upper branch directs pressure,

2-15.

Hydraulic

System--Low-Range

Oper-

through an orifice, to the area between the main

ation

regulator valve and regulator plug. Here, main

a. Main Pressure Circuit (red--fig. 2-4).

pressure forces the plug downward, and forces the

(1) Figure 2-4 illustrates low-range operation

main regulator valve upward. This decreases main

of the transmission while engine throttle is open

pressure.

and the lockup clutch is engaged. The explanations

(9) The lower branch of lockup feed enters the

of circuits and components, below, will refer to

flow valve bore and supplies pressure for lockup

previous explanations where applicable.

operation (except when flow valve is downward).

( 2 ) Oil is pumped into the main pressure

Refer to i below for explanation of the lockup

circuit by both oil pumps (when vehicle is moving

circuit.

forward) in low-range operation. The rear pump

(10) Main pressure enters the flow valve bore

check valve is open (upward) when the rear pump

and acts as described in paragraph 2-14a (6).

is rotating. O i l is distributed as described in

(11) At the main regulator valve, main

paragraph 2-14a (2).

pressure raises the valve as described in paragraph

(3) At the throttle valve, during full-throttle

2-14a (7). However, the valve is moved farther

operation as illustrated, the throttle valve (TV) and

u p w a r d in the bore than shown in figure 2-3,

throttle (T) circuits are charged. Refer to f and g

allowing oil to escape to the sump as well as to the

below for explanations of these circuits.

converter-in circuit. Refer to b below for ex-

(4) At the manual selector valve, main

planation of the converter-in circuit during lockup

pressure is directed to four points. These are the

operation.

front governor check valve ball, low-intermediate

( 1 2 ) At the trimmer valve, main pressure

shift valve. high-intermediate inhibitor circuit, and

enters the valve bore at two points. At the upper

intermediate-low inhibitor circuit. Main pressure

point (orifice at right side of bore), oil fills the area

seats the check valve ball (upward) in the front

above the trimmer plug. Main pressure is at full

governor ( G 1 ) passage and prevents governor

value in this area because no oil can escape past

pressure from exhausting.

the extender valve ball held downward by main

(5) At the low-intermediate shift valve, main

pressure.

pressure divides to two branches. The upper branch

(13) At the lower end of the trimmer valve,

is blocked but the pressure exerted against valve

m a i n pressure enters the trimmer valve bore,

lands of different diameters exerts a downward

connects with the area within the valve through an

force on low-intermediate shift valve. This pressure

orifice. and exerts equal pressure above and below

acts only when the valve is downward and prevents

the valve. The springs above and below the trimmer

cycling of the valve. A similar downward force,

p l u g hold the trimmer plug and valve in the

resulting from unequal valve land diameters, is

positions illustrated. The trimmer is set for action

exerted in the lower branch. These forces act only

when in this condition. Refer to paragraph 2-16i

when the valve is downward. The lower branch

for explanation of trimmer operation.

connects. when the low-intermediate shift valve is

2-11