06 Hoist

HOIST SYSTEM HOLD BRAKE COOLING RELIEF VALVE HOIST RELIEF VALVE LOAD CHECK VALVE

TO HOIST & BRAKE COOLER

HOIST PUMP

777D Off Highway Truck

Adolfo

August 1997

VI. HOIST SYSTEM

1. Components Layout

2. Operation

3. Maintenance

CHAPTER : HOIST SYSTEM

777D Off Highway Truck

VI-1 Page: HOIST CONTROL VALVE HOIST PUMP TRANSMISSION NEUTRALIZER SWITCH CAB ORIFICE PLATE OIL COOLING RELIEF VALVE SLACK ADJUSTER OIL COOLING RELIEF VALVE

777D HOIST SYSTEM

COMPONENT LOCATIONS

HOIST CONTROL VALVE HOIST RELIEF VALVE ORIFICE PLATE HOIST PUMP HOIST RELIEF VALVE

TWO STAGE

HOIST CYLINDER

RAISE

FIRST STAGE

CHAPTER : HOIST SYSTEM

777D Off Highway Truck

VI-3 Page:

TWO STAGE

HOIST CYLINDER

HOIST VALVE

RAISE

CYLINDER HEAD END PORT CYLINDER ROD END PORT CYLINDER HEAD END PORT CYLINDER ROD END PORT TO BRAKE COOLERS RELIEF VALVE FROM

PUMP _{LOAD CHECK VALVE}

DETENT

HOIST VALVE

CHAPTER : HOIST SYSTEM

777D Off Highway T

ruck

HOIST SYSTEM

TO HOIST & BRAKE COOLER

HOIST PUMP

HOIST VALVE

FLOAT

HOIST VALVE

LOWER

PUMP _{LOAD CHECK}

DETENT RELIEF VALVE FROM PUMP DETENT LOAD CHECK FROM CYLINDERS HEAD END TO CYLINDERS ROD END NO FLOW

CHAPTER : HOIST SYSTEM

777D Off Highway T

ruck

HOIST SYSTEM

RAISE

TO DIVERTER VALVE & HOIST/BRAKE COOLER

BRAKE COOLING RELIEF VALVE

Lab A Worksheet

Hoist System Component Reference Checklist

Directions: Place the correct letter next to the component and give a brief description of each. Example: _____ Hoist Pump(s)

Supplies oil flow to the hoist system. The 769D - 777D only have one pump.

Hoist System Components

_____ Hoist Pump

_____ Hoist Control Valve

_____ Hoist Relief Valve

_____ Hoist Diverter Valve

_____ Parking Brake Release Valve

_____ Oil Cooling System Relief Valve

_____ Hoist Lever Switch (Transmission Neutralizer)

CHAPTER : HOIST SYSTEM

777D Off Highway Truck

VI-9 Page:

LAB EXERCISES

Lab B: Adjust Hoist Lever Linkage

This lab allows you to gain hands on experience checking and adjusting the hoist control lever linkage adjustment.

The lab also allows you to gain hands on experience checking the transmission neutralizer switch for correct operation.

Mechanic’s Tool Box and hand tools

Appropriate Service Manual Modules: Hydraulic System Operation, Testing and Adjusting

Check and adjust the hoist control lever linkage on an Off-highway Truck. After the linkage has been checked and adjusted, check for correct

BACKGROUND INFORMATION

MATERIALS NEEDED

INDIVIDUAL OR GROUP EXERCISE

Lab C: Hoist System Diagnostic Testing

This lab allows you to gain hands on experience performing pressure relief, cycle time and drift tests.

Appropriate Service Manual Module Mechanic’s Tool Box and hand tools 1 - 8T0857 Gauge (0-1450 psi) 1 - 8T0859 Gauge (0-3600 psi) 2 - 6V3989 Nipple 2 - 6V4143 Valved Coupler 2 - 6V3079 Diagnostic Hose 2 - 6J3958 1/8-27 NPTF Union 1 - 8T8902 11/16-16 ORFS Tee 1 - Stopwatch 1 - Tape measure

1 - 1U8865 Infrared Thermometer or

1 - 6V9130 Temperature Adapter Group

Perform relief valve pressure, cycle time and drift tests, and record your answers on the appropriate Lab C Worksheet for Off-highway Truck Hoist Test.

CHAPTER : HOIST SYSTEM

777D Off Highway Truck

VI-11 Page:

LAB EXERCISES

769D-777D OFF-HIGHWAY TRUCK

HOIST TEST

Machine Model__________________________ Date __________________________________ Serial # ________________________________ Customer ______________________________ Dealer _________________________________ SMH _________________________________ Serviceman _____________________________ Application ____________________________

VISUAL CHECKS

Oil Level _______________________________ Oil Viscosity ___________________________ Air/Water in Oil? ________________________ Suction Screen Debris? ___________________ Oil Leaks?______________________________ Oil Filter Examination____________________

TEST SPECS ACTUAL

DRIFT RAISE TIME

769D - 777D

HOIST SYSTEM

BRAKE COOLING RELIEF VALVE

HOIST RELIEF VALVE LOAD CHECK VALVE

TO BRAKE COOLER

RAISE

HOIST RELIEF VALVE

LAB D: TRACING HOIST SYSTEM OIL FLOW

CHAPTER : HOIST SYSTEM

777D Off Highway Truck

VI-13 Page:

POST TEST

Directions: Modified True/False. If a question is false, underline or circle the word or words that make

the statement incorrect and replace with word(s) to make the statement correct.

hoist system Example: _____ 1. This is an engine class.

____ 1. Whenever work is performed under the body while the body is raised, you must install the safety pins AND disconnect the hoist control linkage.

____ 2. Incorrect adjustment of the hoist control linkage can prevent the transmission from shifting into reverse.

____ 3. Screens located on top of the hydraulic tank prevent contamination from entering the hoist system.

____ 4. The hoist system pilot operated relief valve controls the maximum pressure in the brake cooling system.

____ 5. An orifice plate at the rod end of the hoist cylinders prevents the body from raising faster than the pump can supply oil to the cylinders (caused by a sudden shift of the load).

Directions: Multiple Choice. Circle the correct letter(s) of the best answer(s) for each question.

6. Supply oil from the hoist pump flows to the brake cooling system when the hoist lever is in the _____ position.

A. Raise B. Lower C. Hold D. Float

7. The _____ holds the hoist lever in the float position after the operator releases the lever. A. ratchet pawl on the hoist lever

B. centering spring on the directional spool C. ball detent on the directional spool D. small gremlin living in the hydraulic tank

8. When the hoist valve is in the hold position with the body raised above the frame, the _____ will prevent the body from lowering.

A. directional spool B. orifice plate C. centering spring D. load check valve

9. If the hoist valve is moved from the hold to the raise position with the body raised above the frame, the _____ will prevent the body from lowering until pump supply pressure is higher than the pressure in the head end of the hoist cylinders.

A. directional spool B. load check valve C. relief valve D. orifice plate

10.When the hoist lever is in the _____ position, a small amount of oil pressure in the rod end of the hoist cylinders holds the body firmly down on the frame to prevent the body from bouncing when traveling without a load in the body.

A. Raise B. Lower C. Hold D. Float

Directions: Match the component with the correct location by placing the letter next to the component.

____ Hoist Supply Pump A. Inside the hydraulic tank

____ Suction Screen B. Rod end port of the hoist cylinders ____ Pilot Operated Relief Valve C. On the hoist valve directional spool ____ Hoist Control Valve D. Below the hoist valve

____ Brake Cooling Relief Valve E. On the pump drive near the torque converter ____ Float Position Ball Detent F. Head end port of the hoist cylinders

____ Transmission Neutralizer Switch G. Behind the hoist pump suction hose in the tank ____ Orifice Plate H. Near the inlet port on the hoist control valve ____ Hoist System Pressure Tap I. Behind the operator’s seat in the cab