Bendix Commercial Vehicle Systems C-300N User Manual

C-300N/C-500N HYDRAULIC POWER STEERING GEAR

SD-30-4265

OUTPUT

SHAFT

OIL RETURN

OIL

SUPPLY

C-500N

NAMEPLATE

OIL RETURN

OIL SUPPLY

SIDE COVER

ADJUSTING

SCREW

OUTPUT

SHAFT

C-300N

NAME PLATE

ADJUSTING

SCREW

VALVE BODY

INPUT

SHAFT

VALVE BODY

STEERING

LIMITING STEM

PLUG

DESCRIPTION

The Compact 300N and 500N (C-300N/C-500N), Hydraulic Power Steering Gears are designed for medium and heavy duty vehicles with front axle weight ratings of 6,000 to 9,000 lbs for the C-300N and up to 15,000 lbs for the C-500N.

They are integral power steering gears incorporating the mechanical and hydraulic actuation and control components in a single cast housing which serves as the power cylinder. The C-300N and C-500N power steering gears are very similar in appearance with the major difference being that the C500N is proportionately larger than the C-300N.

OUTPUT

SHAFT

HOUSING

C-300N

POWER STEERING GEAR

PRESSURE

RELIEF & BYPASS

VALVE CAP NUT

The vehicles steering column is coupled to the gear at the input shaft which transmits steering effort through a recirculating ball screw (spindle assembly) and piston. The piston is an integral part of the power assist and also acts as a steering damper. The direction and degree of power assist is controlled by a rotary hydraulic valve which is integral to the input shaft and spindle assembly. An engine driven hydraulic pump supplies the flow and pressure.

SD-30-4265

TABLE OF CONTENTS

DESCRIPTION .............................................................. 1

OPERATION.................................................................. 1

 General ........................................................................ 1

 Mechanical .................................................................. 3

 Hydraulic ..................................................................... 4

 Rotary Control Valve .................................................... 4

 Steering Limiting Valve ................................................ 7

 Pressure Relief Valve................................................... 8

 Bypass Valve ............................................................... 8

POWER STEERING IDENTIFICATION ......................... 8

PREVENTIVE MAINTENANCE ..................................... 8

 Power Steering Oil ....................................................... 8

 Draining and Filling the System ................................... 8

 Oil Change Intervals .................................................... 8

 Output Shaft Sector Teeth Adjustment .......................... 8

 Output Shaft Boot & Dust Seals ................................... 9

CAUTION NOTE ........................................................... 9

REMOVAL ..................................................................... 9

SPECIAL TOOLS .......................................................... 9

DISASSEMBLY .............................................................11

 General .......................................................................11

 Output Shaft Removal .................................................11

 Piston ........................................................................ 13

 Main Housing & Side Cover ....................................... 15

 Valve Body & Spindle ................................................ 16

 Output Shaft .............................................................. 18

 Pressure Relief & Bypass Valve ................................ 18

 Spindle ...................................................................... 18

CLEANING & INSPECTION ........................................ 19

REASSEMBLY ............................................................. 19

 General ...................................................................... 19

 Valve Body & Spindle ................................................ 19

 Piston ........................................................................ 21

 Housing ..................................................................... 24

 Output Shaft & Side Cover ......................................... 25

ADJUSTMENT ............................................................ 26

 Piston to Output Shaft Gear Backlash ........................ 26

 Stroke Limiting Stem.................................................. 27

ON-VEHICLE POWER STEERING TESTS ................ 27

 Preliminary ................................................................ 28

 Pressure Relief Valve................................................. 28

 Internal Leakage ........................................................ 28

TECHNICAL DATA ...................................................... 29

ASSEMBLY TORQUE CHART .................................... 29

TROUBLESHOOTING ................................................ 30

PISTON OVER OUTPUT SHAFT MOUNTING

(LEFT HAND THREAD SPINDLE)

PISTON UNDER OUTPUT SHAFT MOUNTING

(RIGHT HAND THREAD SPINDLE)

PISTON

OUTPUT

SHAFT

SPINDLE

ASSEMBLY

INPUT

SHAFT

PITMAN

ARM

STEERING

WHEEL

VEHICLE

RIGHT

TURN

VEHICLE

LEFT

TURN

OUTPUT

SHAFT

PISTON

SPINDLE

ASSEMBLY

INPUT SHAFT

STEERING

WHEEL

PITMAN

ARM

FIGURE 1 - MECHANICAL OPERATION

OPERATION

GENERAL

Both steering gears are composed of mechanical and hydraulic power assist components.

Actual steering is accomplished mechanically. Effort applied at the vehicles steering wheel results in mechanical movement within the steering gear which causes the vehicle to change its direction of travel. The hydraulic power assist components function solely to reduce the mechanical effort required to turn the vehicles steering wheel. Loss of hydraulic power will in no way prevent the vehicle from being maneuvered mechanically, however greater effort will be required to turn the steering wheel.

MECHANICAL OPERATION

The turning effort exerted by the driver on the steering wheel is transmitted to the input shaft which is part of the spindle assembly. The spindle and piston function like a screw and nut through the action of a chain of recirculating balls that serve as an interface. Rotation of the spindle causes axial movement of the piston within the power cylinder. Gear teeth, cut directly into the piston, mesh with corresponding gear teeth on the output shaft. As the piston moves, the output shaft and the attached pitman arm are rotated. Figure 1

Spindle and piston sets are provided with either right or left hand screw threads. Figure 2 The manner in which the steering gear is mounted on the vehicle determines of the thread used. Figures 1, 2 & 3

LEFT HAND

THREAD

INPUT

SHAFT

BALL

SCREW

RIGHT HAND

THREAD

FIGURE 2 - SPINDLE ASSEMBLIES

TIE ROD

ARM

STEERING

ROD

ARM

TIE

DRAG

LINK

PITMAN

ARM

SPINDLE

ASSEMBLY

PISTON UNDER

OUTPUT SHAFT

FIGURE 3 - POWER STEERING GEAR MOUNTING CONFIGURATION

When the steering gear is mounted on the vehicle in a position similar to the piston under output shaft illustration in figure 1, the piston and spindle used will have a right hand thread. A left hand thread is required when the steering gear is mounted in a position similar to the piston over output shaft illustration. In either mounting position, a right turn is accomplished when the input shaft is rotated clockwise and the output shaft, along with the pitman arm, rotate toward the rear of the vehicle.

HYDRAULIC OPERATION

GENERAL

Functioning together, the spindle and valve body assemblies serve as a means of flow and pressure control for the power assist portion of the steering gear. All hydraulic fluid enters and exits the power steering gear through lines connected to the threaded ports in the valve body.

steering gear rather than being forced to and from the power steering pump and reservoir. Figure 9

The spindle assembly rotates on a ball bearing in the bore of the valve body. The spindle is composed of three major parts;, the input shaft, torsion bar, and ball screw. One end of the input shaft is finely splined for connection to the steering column while the other end has a coarse spline which mates loosely with a similar spline inside the ball screw. The coarse splines form mechanical stops which limit the amount of relative rotation between the ball screw and input shaft. Six evenly distributed longitudinal grooves are machined into the outer surface of the input shaft and correspond to six grooves machined into the bore of the ball screw. The torsion bar is pinned to the ball screw and input shaft and forms a spring connection between the two. With the input shaft inserted into the ball screw the six grooves of each of these components alternate with each other and form the hydraulic rotary control valve. Holes on the outside surface of the ball screw extend into the six

The valve body assembly forms a closure for the housing

grooves within its bore. Figure 5

and provides a means of retaining the spindle assembly. It contains a series of circular channels and radial passages which serve to direct the flow of hydraulic oil into and out of the rotary control valve in the spindle assembly. In addition, the valve body can contain an optional pressure relief and bypass valve. The pressure relief valve ensures that a preset maximum pressure is not exceeded. It is always set at a pressure level below that of the power steering pump relief valve and is intended to limit the power assist to a specific maximum level. Figure 8

These holes allow pressurized oil to enter and exit the two parts of the rotary control valve. There are three groups of holes in the ball screw. Each group is made up of three different size holes which form a diagonal line across the surface of the ball screw. The largest hole in each group conducts pressurized oil into the grooves of the rotary control valve. The second largest hole in each group conducts oil out of the rotary control valve to the side of the power piston furthest from the rotary control valve while the smallest hole conducts oil to the closest side of the piston.

The optional bypass valve is intended to lessen the manual

Figures 5 & 6

steering effort required in the event hydraulic pressure is lost. The bypass valve permits fluid to circulate within the

PISTON OVER

OUTPUT SHAFT

SIDE VIEW

HOUSING

PISTON

STEERING

LIMITING STEM

POPPET

SEAT

POPPET

VALVE

OUTPUT

SHAFT

RACK AND

SECTOR GEAR

RECIRCULATING

BALLS

TORSION BAR

STEERING

LIMITING

STEM

BALL SCREW

ROTARY VALVE

VALVE BODY

SPINDLE

ASSEMBLY

INPUT

SHAFT

VALVE NUT

OUTPUT

SHAFT

END

VIEW

DUST BOOT

DUST

SEAL

RACK AND

SECTOR GEAR

RECIRCULATING

BALLS

PISTON

HOUSING

POPPET VALVE

SEAT

SEAL AND

BACKUP RING

ROLLER

BEARINGS

NAMEPLATE

STEERING

LIMITING STEM

ADJUSTING

SCREW SPACER

ADJUSTING

SCREW

ADJUSTING

SCREW LOCK

SIDE COVER

BALL TUBE

COVER

BALL TUBE

STEM PLUG

C-500N DETAIL

NUT

FIGURE 4 - POWER STEERING GEAR

BALL SCREW

(ROTARY VALVE

OUTER ELEMENT)

TORSION

BAR PIN

SPINDLE ASSEMBLY

OIL IN

SUPPLY

OIL OUT

LEFT TURN

BALL SCREW

(OUTER VALVE ELEMENT)

OIL OUT

RIGHT TURN

ROTARY VALVE LONGITUDINAL

GROOVES (6)

(INSIDE HIDDEN

FROM VIEW)

OIL IN

OIL OUT LEFT

TURN

PIN HOLE

INPUT SHAFT &

TORSION ASSEMBLY

OIL OUT RIGHT TURN

TORSION BAR

OIL OUT (RIGHT TURN)

OIL RETURN HOLES

(HIDDEN FROM VIEW)

INPUT SHAFT (INNER

VALVE ELEMENT)

STEERING

STOP

SPLINES

OIL RETURN (TO

PUMP RESERVOIR)

INNER VALVE

ELEMENT GROOVE

RETURN

HOLE

ROTARY

VALVE

GROOVES

(6)

INPUT SHAFT

(ROTARY VALVE

INNER ELEMENT)

(FROM PISTON CAVITY)

OIL RETURN

HOLES (TO

PUMP RES.)

OIL

TORSION BAR PIN

SPINDLE ASSEMBLY

FIGURE 5 - SPINDLE ASSEMBLY WITH ROTARY VALVE COMPONENTS

ROTARY CONTROL VALVE OPERATION

The rotary control valve is an open center type which allows a continuous flow of oil (through the longitudinal grooves in the input shaft and bore of the ball screw) when held in the neutral position by the torsion bar.

When steering effort is applied, the input shaft and ball screw tend to turn in unison, however the spring action of the torsion

TORSION BAR

OIL OUT

(LEFT TURN)

bar results in the input shaft rotating slightly in advance of the ball screw. The six pairs of grooves that form the rotary control valve are displaced from their neutral flow position. As steering effort increases, so does the amount of displacement. Depending on the direction steered, the groove displacement of the input shaft directs hydraulic oil through the appropriate drilled passages in the ball screw to one side or the other of the piston. Hydraulic pressure acting

INPUT SHAFT (INNER

VALVE ELEMENT)

OIL IN

SUPPLY

OIL RETURN (TO

PUMP RES.)

OUTER VALVE

ELEMENT GROOVE

BALL SCREW

(OUTER VALVE

ELEMENT)

PUMP

RES.

OIL IN

OIL

RETURNING

FROM RIGHT

TURN SIDE OF

POWER PISTON

FIGURE 8 - ROTARY VALVE OPERATION

OIL OUT

(LEFT TURN)

LEFT TURN

OIL OUT

RIGHT

TURN

OIL IN

OIL OUT

(LEFT TURN)

NEUTRAL

PUMP

RES.

OIL OUT

RIGHT

TURN

OIL IN

OIL RETURNING

FROM LEFT TURN

SIDE OF POWER

PISTON

PUMP

RES.

RIGHT TURN

EXTREME LEFT TURN POSITION POPPET VALVE OPEN EXTREME RIGHT TURN POSITION POPPET VALVE OPEN

SPRING

OUTPUT

SHAFT

BALL

PISTON

SCREW

SPINDLE ASSEMBLY

LIMITING

PRESSURIZED SIDE OF PISTON DURING

LEFT TURN

INPUT

SHAFT

STEM

RETURN

SIDE OF

PISTON

HOUSING

POPPET

VALVE

POPPET VALVE

PISTON

POPPET SEAT

ADJUSTABLE STEM

O-RING

FIGURE 7 - STEERING LIMITING POPPET VALVE OPERATION

upon the piston surface eliminates much of the pistons resistance to movement. Spring force exerted by the torsion bar causes the ball screw to rotate as piston resistance is removed. As the ball screw rotates, the relative groove displacement is eliminated and the rotary valve returns to a neutral position.

Moderate effort at the steering wheel produces smaller valve displacements and lower power assist, thus providing good steering feel. At Increased displacements, the pressure rises more rapidly giving increased power assistance and quicker response. Maximum pressure is developed after approximately 30 displacement giving a direct feel to the steering. Groove displacement is limited by the clearance of the stop spline mesh between the input shaft and ball screw. The splines take up the steering movement while allowing the torsion bar to hold the groove displacement. The torsion bar and stop splines form two parallel means of transmitting the steering torque. When no steering torque is applied, the torsion bar returns the valve grooves to a neutral position allowing the pressurized oil to flow to the return line. Figures 5 & 6.

OUTPUT

SHAFT

INPUT

SHAFT

PRESSURIZED SIDE

DURING RIGHT TURN

PISTON

LIMITING

STEM

POPPET VALVES

(STEERING LIMITING)

steering linkages and components. Figure 7 When this feature is incorporated in the C-300N, only one of the two steering limiting stems is externally adjustable. Both steering limiting stems in the C-500N are externally adjustable. Figure 4.

PRESSURE RELIEF VALVE OPERATION

The pressure relief valve is an option. Located in the valve body, the pressure relief valve limits hydraulic pressure within the power steering gear to a preset maximum. While the setting of the pressure relief valve may be adjusted to various levels depending upon part number and application, it is always set to a pressure lower than the relief valve on the power steering pump. Figure 8.

OIL

RETURN

CHANNEL

INPUT

SHAFT

POWER

STEERING

GEAR

HOUSING

VALVE BODY

PRESSURE

RELIEF

VALVE PLUG

ADJUSTING

SHIMS

SPRING

SEAT

STEERING LIMITING VALVE OPERATION

In steering gears equipped with steering limiting valve, power assisted movement of the piston within its bore is limited by poppet valves installed in both piston faces. As the piston approaches its extreme travel in either direction, a stem unseats the steering limiting poppet valve. Some hydraulic power assist is removed as pressurized oil passes around the poppet valve to the other side of the piston and to the return line. Continued movement of the piston will result in removal of increasing amounts of power assist and cause increased steering effort. Steering limiting reduces the maximum power assist that can be transmitted to the axle

PRESSURE

RELIEF VALVE

& PISTON

BYPASS

VALVE

OIL RETURN

PORT

FIGURE 8 - PRESSURE RELIEF VALVE OPERATION

OIL SUPPLY

PORT

OIL

RETURN

CHANNEL

INPUT

SHAFT

POWER

STEERING

GEAR

HOUSING

VALVE

BODY

BENDIX ASSEMBLY

PART NUMBER

VEHICLE

MFGR

PART

NUMBER

SERIAL NUMBER

MONTH ASSEMBLED

(A = JAN., ETC.

SPRING

BYPASS

VALVE

OIL RETURN

PORT

FIGURE 9 - BYPASS VALVE OPERATION

OIL SUPPLY

PORT

BYPASS VALVE OPERATION

The optional bypass valve is located adjacent to the pressure relief valve in the valve body.

When it is necessary to steer the vehicle without the power steering pump in operation, the bypass valve permits oil to flow from the return to the supply passages within the steering gear. As the power piston moves inside the housing, oil displaced from one side is transferred to the other through the bypass valve thus preventing reservoir flooding and cavitation in the pressure line. Figure 9

POWER STEERING GEAR IDENTIFICATION

LOCATION OF

MANUFACTURE

POWER STEERING GEAR NAMEPLATE INFORMATION

YEAR ASSEMBLED

(LAST DIGIT)

2. Remove the drain plug (54) and seal washer(53) or disconnect the return line at the valve body outlet port. (The outlet port is identified by the arrow which flows out of the gear.) Turn the steering wheel to the left as far as it will go. Run the engine for 10 seconds at the most until the oil is drained from the reservoir and pump. Switch off the engine and turn the steering wheel backwards and forwards from full lock to full lock until all the oil is drained out.

3. Clean the outside of the reservoir. Remove and replace the old filter element.

4. Fill reservoir full of oil.

5. Turn the engine over with the starter motor. (Must be done in a manner that the engine does not start.) Add oil as the level drops to avoid air being drawn into the system.

6. When the oil level reaches the full mark on the dipstick, start the engine and turn the steering wheel slowly from side to side until air bubbles cease to appear in the reservoir. Refill reservoir to full mark on the dipstick.

7. The oil level should be checked every 2,000 miles. The correct level is between the minimum and maximum level marks on the dipstick with the engine stopped.

A nameplate is attached to the exterior of the housing generally on one of the mounting lugs. The information found on the name tag is illustrated

PREVENTIVE MAINTENANCE

POWER STEERING OIL

It is important that an approved oil be used to ensure proper operation of the power steering unit. The vehicle manufacturers recommendations should be adhered to.

Once an oil type is in use, it should never be mixed with any other type. If it should become necessary to change types of oil, the entire system must be drained following the procedure below.

DRAINING AND FILLING THE SYSTEM

1. Lift the front axle sufficiently to raise the wheels clear of the ground.

OIL CHANGE INTERVALS

It is recommended that the oil be changed at 40,000 mile intervals and at the time of rebuild. Beyond its function as the media for transmitting power, the oil also serves to lubricate and dissipate heat. Carefully clean, inspect, and replace if necessary all filter elements in the pump system including vents and breathers.

OUTPUT SHAFT SECTOR TEETH ADJUSTMENT

The gear lash or preload between the piston teeth and sector gear should not require attention in normal service, however a provision for adjustment is provided.

Adjustment requires that the steering gear be drained and the pitman arm and input shaft be disconnected from the vehicle. The adjustment procedure is described at the end of the assembly section of this manual.

EXTERIOR BOOTS AND DUST SEALS

REMOVING THE POWER STEERING GEAR

Inspect the integrity of the output and input shaft boot and dust seal. These components prevent contamination from entering the housing around the shaft. If deterioration is noted, these components should be replaced. The cavities between the boots and seals should be filled with special high temperature grease.

IMPORTANT! PLEASE READ AND FOLLOW THESE INSTRUCTIONS TO AVOID PERSONAL INJURY OR DEATH:

When working on or around a vehicle, the following general precautions should be observed at all times.

1. Park the vehicle on a level surface, apply the parking brakes, and always block the wheels.

2. Stop the engine when working around the vehicle.

3. If the vehicle is equipped with air brakes, make certain to drain the air pressure from all reservoirs before beginning ANY work on the vehicle.

4. Following the vehicle manufacturers recommended procedures, deactivate the electrical system in a manner that removes all electrical power from the vehicle.

5. When working in the engine compartment the engine should be shut off. Where circumstances require that the engine be in operation, EXTREME CAUTION should be used to prevent personal injury resulting from contact with moving, rotating, leaking, heated, or electrically charged components.

6. Never connect or disconnect a hose or line containing pressure; it may whip. Never remove a component or plug unless you are certain all system pressure has been depleted.

7. Never exceed recommended pressures and always wear safety glasses.

8. Do not attempt to install, remove, disassemble or assemble a component until you have read and thoroughly understand the recommended procedures. Use only the proper tools and observe all precautions pertaining to use of those tools.

9. Use only genuine Bendix replacement parts, components, and kits. Replacement hardware, tubing, hose, fittings, etc. should be of equivalent size, type, and strength as original equipment and be designed specifically for such applications and systems.

10. Components with stripped threads or damaged parts should be replaced rather than repaired. Repairs requiring machining or welding should not be attempted unless specifically approved and stated by the vehicle or component manufacturer.

11. Prior to returning the vehicle to service, make certain all components and systems are restored to their proper operating condition.

1. Mark or identify the inlet and return lines at the valve body ports.

2. Drain the system following the instructions presented under Preventive Maintenance. Remove both inlet and return lines.

3. Disconnect the steering column at the input shaft following the vehicle manufacturers instructions.

4. Disconnect the pitman arm from the vehicles steering linkage using the vehicle manfacturers instructions.

CAUTION: If it is necessary to remove the pitman arm before the steering gear is removed from the vehicle,

DO NOT USE HEAT OR POUND ON THE PITMAN ARM OR OUTPUT SHAFT as damage can result. Do

not attempt repairs to these components. They must be replaced if damaged. Use a large gear puller to remove the pitman arm such as Snap-On puller #CG-283 or Ford part number T64P-3590-F.

PART NUMBER 106234 (REQUIRED)

SPANNER WRENCH - REQUIRED FOR REMOVAL

AND INSTALLATION OF THE VALVE NUT.

PART NUMBER 297676 (REQUIRED)

SEATING TOOL - REQUIRED TO FORM TEFLON GLIDE RINGS

AND TO INSTALL SPINDLE ASSEMBLY IN VALVE BODY.

PART NUMBER 298077 (OPTIONAL)

PILOTED SCREWDRIVER - USED TO REMOVE AND

INSTALL THE PRESSURE RELIEF VALVE SEAT.

PART NUMBER 106762 (OPTIONAL)

HOLDING FIXTURE - USED TO HOLD THE PISTON AND

VALVE BODY DURING ASSEMBLY AND DISASSEMBLY.

FIGURE 10 - TOOLS FOR ASSEMBLY/DISASSEMBLY

C-500N DETAIL OF VALVE

BODY AND STEERING

LIMITING STEM

RETURN TUBE STYLE

FOR C-300/N/C-500N

ALTERNATE BALL

1. Valve Nut

2. External Dust Seal

3. Spindle Assembly

4. Internal Dust Seal

5. Seal

6. Ball Cage

7. Valve Body

8. Ball Race

9. Ball

10. Teflon Ring

11. O-Ring

12. O-Ring

13. Steering Limiting Stem

14. Seal Ring

15. O-Ring

16. Spring

17. Valve Seat

18. Sealing Washer

19. Steering Limiting Stem

20. O-Ring

21. Plug

22. Housing

23. Piston

24. Tube Cover

25. Output Shaft

26. Rollers

27. O-Ring

POWER STEERING PARTS LIST

28. Backup Ring

29. Seal & Backup Ring

30. Retaining Ring

31. Side Cover

32. Nut

33. Adjusting

34. Adjusting Screw Spacer

35. Ball Tube

36. Retaining Ring

37. O-Ring

38. Dust Seal

39. Dust Boot

40. Bolt

41. Adjusting Shims

42. Pressure Relief Valve Plug

43. Spring

44. Sealing Washer

45. Spring Seat

46. Valve Piston

47. Seal Washer

48. Valve Seat

49. Bolt

50. Retaining Ring

51. Bypass Valve Spring

52. Bypass Ball Valve

53. Seal Washer

54. Drain Plug

FIGURE 7 - C-300N / C-500N POWER STEERING GEAR

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