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h. Protection in the Event of Electrical Interruption 1. The shift valves (except for the splitter shift valve) are arranged in a cascade system. This arrangement ensures that only one range clutch can be applied at a given time, because the ap-ply pressure of each depends upon the released position of the preceding valve. If two valves should be in the apply position, only the one that is first in line can receive apply pressure.

2. For models with lock-in-range, each of the for-ward operation shift valves directs its clutch apply pressure to the spring cavity beneath the valve at the same time the clutch is charged.

This ensures that the valve will remain in its upward position (clutch applied) even though the solenoid at the upper end of the valve is de-energized (by electrical interruption). This hy-draulic “hold” can be relieved only by the up-ward movement of an adjacent shift valve, or in the case of the low-range shift valve, by en-ergizing Solenoid A. The splitter shift valve, in splitter-low position, is unlocked by energizing Solenoid G to exhaust the pressure from be-neath the valve. These features are referred to as lock-in-range, because the operating range is retained even though an electrical interrup-tion occurs during operainterrup-tion.

3. Models with lock-in-neutral will shift into neu-tral from any range if an electrical interruption occurs.

4. For all models, the reverse shift valve will al-ways go to neutral (exhaust position) if an electrical interruption occurs during reverse operation.

i. Trimmer System

1. The trimmer system includes four valve groups in the lower section of the control valve assem-bly. These are: reverse trimmer, low-range trimmer, intermediate-range trimmer, and split-ter-low trimmer.

2. The functions of the four trimmers are similar.

Each trimmer regulates the application of its corresponding clutch, preventing shift shock from abrupt clutch engagement. Each trimmer initially limits the apply pressure of its clutch, and then permits full apply pressure. Spring force returns the valves to operating position.

3. A secondary function of the low-range, inter-mediate-range, and splitter-low trimmers is a regulation of the exhaust of preceding clutches.

This prevents both clutch slippage and exces-sive clutch overlap during shifting.

CAUTION:

Loss of hydraulic pressure (such as caused by stopping the engine) relieves all hydraulic holds.

Only neutral will be obtained when the engine is restarted following an electrical interruption.

4. Individual trimmer system valve groups are de-scribed in Paragraphs 2–21j through 2–21m.

j. Reverse Trimmer

1. The reverse trimmer valve group includes a valve stop and two springs in the lower end of the valve bore, a valve near the middle of the bore, and a spring and valve at the upper end of the bore. Refer to Items 75 through 80 (Foldout 21). A reverse-clutch pressure passage is con-nected to the upper end of the bore. An exhaust port is provided just below the reverse clutch pressure passage.

2. When the reverse clutch is applied, apply pres-sure is sent to the top end of the upper valve.

Initially, the upper and lower valves are forced downward against the springs until transmis-sion fluid escapes at the exhaust port. The es-cape of fluid, as long as it continues, reduces clutch-apply pressure. However, fluid flows through an orifice in the trimmer upper valve to the cavity between the upper trimmer valve and the lower trimmer valve. Hydraulic pres-sure in this cavity forces the lower valve far-ther downward to the stop. The lower valve stops, but the flow through the orifice contin-ues. The pressure below the upper trimmer valve plus the spring force is greater than the hydraulic pressure acting on the upper end of the valve. This causes the upper trimmer valve to move back up. This throttles, then stops, the escape of fluid through the exhaust port. When the escape of fluid is throttled, clutch pressure rises. When the escape of fluid stops, clutch pressure is maximized. The lower valve re-mains downward until the clutch is released.

3. Upon release of the clutch, the spring pushes all the trimmer components to the top of the valve bore. In this position, the trimmer is reset and ready for the next clutch application.

k. Low-Range Trimmer

1. The low-range trimmer valve group includes a valve stop and two springs at the lower end of the trimmer valve bore, a valve near the middle of the bore, and a trimmer valve and spring at the upper end of the bore. Refer to Items 69 through 74 (Foldout 21). A low-range clutch pressure passage is connected to the upper end

of the bore. An exhaust port is provided just be-low the be-low-range clutch pressure passage.

2. Exhaust passages from the low-range and high-range shift valve bores connect to the trimmer bore near the middle of the bore.

These passages, in conjunction with the posi-tion of the trimmer lower valve, control the ex-haust rates of preceding clutches.

3. The trimming function of the low-range trim-mer is similar to that of the reverse trimtrim-mer (Paragraph 2–21j).

l. Intermediate-Range Trimmer

1. The intermediate-range trimmer valve group in-cludes a valve stop and two springs at the lower end of the trimmer valve bore, a valve near the middle of the bore, and a trimmer valve and spring at the upper end of the bore. Refer to Items 63 through 68 (Foldout 21). An intermedi-ate-range clutch pressure passage is connected to the upper end of the bore. An exhaust port is provided just below the intermediate-range clutch pressure passage.

2. Exhaust passages from the intermediate-range shift valve and to the exhaust regulator valve are provided. These passages, in conjunction with the position of the trimmer lower valve, control the exhaust rate of the low-range clutch.

3. The trimming function of the intermediate-range trimmer is similar to that of the reverse trimmer (Paragraph 2–21j).

m. Splitter-Low Trimmer

1. The splitter-low trimmer valve group includes two springs and a valve stop in the lower end of the trimmer valve bore, a trimmer lower valve at the middle of the bore, and a spring and trimmer upper valve at the upper end of the valve bore. Refer to Items 53 through 58 (Fold-out 21). A splitter-low clutch pressure passage is connected to the upper end of the trimmer valve bore. An exhaust port is provided just be-low the splitter-be-low clutch pressure passage.

An exhaust passage from the splitter shift valve bore is connected to the middle of the trimmer valve bore. An exhaust port is provided just

be-low the splitter exhaust passage and another at the lower end of the trimmer valve bore.

2. The trimming function of the splitter-low mer valve is similar to that of the reverse trim-mer (Paragraph 2–21j).

3. A secondary function of the splitter-low trim-mer is the regulation of splitter-high clutch ex-haust. The position of the splitter-low trimmer valve, in relation to the exhaust passages near the middle of the trimmer valve bore, deter-mines the exhaust rate of the splitter-high clutch exhaust.

n. Exhaust Regulator Valve

1. The exhaust regulator valve group includes a valve guide pin, a spring, and a mushroom-shaped valve. The valve seats in an opening in the separator plate adjacent to the control valve body. The spring maintains a slight force to hold the valve in its seat (closed).

2. The exhaust regulator valve is a common point through which several exhaust passages lead.

This arrangement provides an exhaust system which dissipates almost all hydraulic pressure, but yet retains fluid in the system to enable quick response.

o. Solenoids

1. For lock-in-range models, the system includes seven solenoids. These are identified as Sole-noids A, B, C, D, E, F, and G in illustrations and explanations.

2. For lock-neutral models, the system in-cludes five solenoids. These are identified as Solenoids B, C, D, E, and F in illustrations and explanations.

3. These solenoids are identical components and are not marked for identification. Electrical leads which connect to the solenoids are marked.

4. A solenoid electrically produces a magnetic pulling force when energized. The magnetic force lifts a plunger which allows a check ball in the solenoid to unseat. The unseated check ball opens a port which bleeds off hydraulic pressure at the end of the shift valves faster than the pressure can be sustained by fluid coming into the area through an orifice. This

permits the shift valve spring to push the shift valve toward the solenoid (or relieves pressure at the spring end of valve).

5. Solenoids are designed to be actuated by either 12V or 24V. The manual-electric control has solenoids that match the voltage rating of the equipment electrical system.

p. Shift Selector Assembly (Foldout 33)

1. The shift selector assembly (shift tower) is manually operated and has eight selector posi-tions. These are (from rear to front): Reverse, Neutral, First, Second, Third, Fourth, Fifth, and Sixth. The range indicator is correspond-ingly marked R, N, 1, 2, 3, 4, 5, and 6. Each shift position is gated, and the selector lever must be pushed right or left, alternately, to clear the gate separating each shift position from the adjoining position.

2. Eight microswitches are operated by a cam at-tached to the manual selector lever. Each posi-tion of the lever opens and closes the switches required to energize or de-energize the proper combination of solenoids for that selector posi-tion.

3. A solenoid which has its axis on a line with the axis of the switch-operating cam acts as a downshift inhibitor. It is energized when the transmission lockup clutch engages. Lockup clutch pressure closes the pressure-actuated switch, which in turn energizes the inhibitor solenoid. The inhibitor solenoid engages a dog clutch arrangement which prevents the shift se-lector lever from being moved to a lower range position. The shift selector lever may be up-shifted.

4. A lamp, which illuminates a translucent shift guide, is included in the shift selector assem-bly. It is connected to the equipment dash lamp circuit. Both 12V and 24V systems use a 12V lamp. A resistor is in series with the lamp in 24V systems.

q. Wiring Harness

1. A wiring harness connecting the selector as-sembly to the valve body asas-sembly transmits the electrical signals that cause the transmis-sion to respond to the movements of the shift selector.

2. Fourteen wires are in the harness at the point where it leaves the selector assembly. Six wires branch off from the harness to attach to various parts of the circuit. The remaining eight wires attach to the main control valve body.

3. A sixteen-pin female connector is attached to the selector end of the wiring harness. An eight-pin female connector is attached to the control valve body end of the harness. These connectors push onto mating connectors on the selector assembly and valve bodies. A nut at each connector is tightened to secure the har-ness ends.

2–22. MANUAL-ELECTRIC CONTROL HYDRAULIC SYSTEM CIRCUITS (Foldout 6)

NOTE:

• References to up, down, left, or right refer to posi-tions or movements of components on Foldout 6.

• For manual-electric control system functions, refer to Paragraph 2–18a.

• For manual-electric control system schematics, re-fer to Paragraph 2–18b.

a. Neutral

1. The shift selector is in neutral, the equipment engine is idling, and the transmission fluid tem-perature is normal at 180–200˚F (83–93˚C). The input pump, driven when the engine is operat-ing, picks up transmission fluid from the sump and pumps it into the hydraulic system.

2. The transmission fluid flows through the filters to the main-pressure regulator valve. From the regulator valve, the fluid flows to the lockup shift valve and the flow valve. Fluid at the lockup shift valve is stopped at the valve. At the flow valve, fluid must flow through an ori-fice. If the circuit beyond the valve requires fluid, then the fluid moves the valve, bypassing the orifice, and flows unrestricted through the flow valve. When the flow valve moves, fluid at the larger diameter end of the valve unseats the

check valve and enters the main hydraulic cir-cuit (red) beyond the flow valve.

3. Even though the action of the flow valve oc-curs every time there is a significant flow of fluid through it, the primary purpose of the flow valve is to disengage the lockup clutch during an upshift or downshift, automatically placing the transmission in converter opera-tion. At that time, the movement of the flow valve opens the ports that exhaust the lockup clutch and shuts off the fluid supply.

4. Main pressure (red), leaving the flow valve, is directed to the solenoid pressure regulator valve and to the priority valve. At the solenoid pressure regulator valve, a regulated solenoid pressure (yellow/white) for controlling the shift valves is produced and directed to each shift valve. At each shift valve, the fluid must pass through an orifice. At the priority valve, fluid passes through an orifice and exerts up-ward pressure on the step diameter of the valve. In a parallel branch, fluid flows beneath the lower end of the priority valve and is di-rected to the splitter shift valve, two points on the high-range shift valve, and the low-range shift valve.

5. At the reverse shift valve, Solenoid B is de-en-ergized and its check ball is seated. This retains solenoid pressure and the valve is pushed downward against its spring. The reverse clutch is exhausted through the spring-loaded exhaust regulator valve.

6. At the low-range shift valve, Solenoid C is de-energized and its check ball is seated. For mod-els with lock-in-range, Solenoid A is energized and its check ball is unseated. For models with lock-in-neutral, Solenoid A is not present. So-lenoid pressure at the upper end of the valve holds the valve downward against its spring.

The low-range clutch is exhausted via the bore of the intermediate-range shift valve, through the spring-loaded exhaust regulator valve, and through the unseated check ball of Solenoid A (if present).

7. At the intermediate-range shift valve, Solenoid D is de-energized, and its check ball is seated.

Solenoid pressure, retained at the upper end of the valve, forces the valve downward against its spring. The intermediate-range clutch is ex-hausted through the high-range shift valve bore (valve downward), through the low-range trim-mer valve bore, and then through the spring-loaded exhaust regulator valve.

8. At the high-range shift valve, Solenoid E is de-energized and its check ball is seated. Solenoid pressure retained at the upper end of the shift valve forces the valve downward against its spring. The high-range clutch is exhausted di-rectly through a hole in the separator plate.

9. At the splitter shift valve, Solenoid F is ener-gized and its check ball is unseated. Solenoid G (if present) is de-energized and its check ball is seated. No pressure is retained at the upper end of the valve, and the spring at the lower end of the valve pushes the valve upward. With the valve in its upward position, pressure is di-rected to the splitter-low clutch (red/white) and applies the clutch. Splitter-low clutch pressure is also directed to the splitter-low trimmer valve. The splitter shift valve remains upward until Solenoid F is de-energized and Solenoid G (if present) is energized.

b. Protection in the Event of Electrical Interrup-tion While Operating in Neutral

1. Protection in the event of electrical interruption while operating in neutral, as covered herein, concerns only the design of the system to pro-vide certain safeguards in the event of interrup-tion of electrical power to the solenoids.

2. If total electrical power is interrupted while the transmission is operating in neutral, the transmission will remain in neutral (engine running) regardless of any position which might be manually selected after the interrup-tion. Partial electrical interruption (one sole-noid loses power) while operating in neutral will permit the transmission to continue oper-ation in neutral if the selector lever is not moved. If electrical power to individual Sole-noid A (if present) or SoleSole-noid F is inter-rupted while operating in neutral, erratic

shifting can be expected if other selector posi-tions are selected. Refer to Troubleshooting (Paragraph 3–23).

c. Protection in the Event of Electrical Interrup-tion While Operating in Forward Ranges 1. For models with lock-in-range, if electrical

power is interrupted completely during opera-tion in any forward range, the transmission will continue operation in that range if the equip-ment engine is not stopped.

2. If the shift selector is moved, that same range will be maintained in all selector lever posi-tions. If the engine is stopped, the transmission will go to neutral when the engine is restarted.

3. If electrical power to the individual energized solenoids is interrupted during operation in any forward range, the transmission will continue in that same range until shifted out of that range or until the engine is stopped. Thereafter, shifting will be erratic in other selector positions. Refer to Troubleshooting (Paragraph 3–23).

4. For models with lock-in-neutral, if electrical power is interrupted completely during opera-tion in any range, the transmission will shift to neutral.

d. First-Range Operation

1. When the selector lever is moved from N