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Steering and Alignment

Steering and Alignment. Objectives. • Identify the components of the steering system of a heavy-duty truck. • Describe the procedure for inspecting front axle components for wear.

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Steering and Alignment

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  1. Steering and Alignment

  2. Objectives • Identify the components of the steering system of a heavy-duty truck. • Describe the procedure for inspecting front axle components for wear. • Explain how toe, camber, caster, axle inclination, turning radius, and axle alignment affect tire wear, directional stability, and handling.

  3. INTRODUCTION The steering system in a heavy-duty truck is expected to deliver precise directional control of the chassis at both gross and unloaded vehicle weight. It has to be able to minimize driver effort while retaining some road feel. Truck steering systems can be either manual or power-assisted.

  4. Manual Steering Gear Components.

  5. STEERING GEAR The steering gear is a gearbox that both multiplies steering input torque and changes its direction. Truck steering systems do not use rack and pinion-type steering gear. There are two general categories of heavy-duty steering gears: • Worm and sector shaft • Recirculating ball

  6. Components • Steering gearbox is connected to the Pitman Arm • Pitman Arm is connected to the Drag Link • Drag Link is connected to the Steering Arm • Steering Arm is connected to the Steering Knuckle • Steering Knuckle is mounted to the axle and has the Ackerman arm attached to it • Ackerman arm has a tie rod cross tube connected to it that goes to the other Steering Knuckle

  7. PITMAN ARM, DRAG LINK

  8. STEERING KNUCKLE

  9. Tapered knuckle pin straight knuckle pin

  10. FRONT-END ALIGNMENT

  11. Measuring Toe 1/16 inch +or- 1/32 toe in Always the final adjustment

  12. Deep Drop Tie-Rod Ends

  13. CASTER

  14. Recommended Caster Settings • Tandem drive axle: 1/2–1 1/2 degrees positive • Single drive: 1 1/2– 2 1/2 degrees positive • No more than 1/2 degree difference between the left and right wheels • Positive caster on the left wheel should not be greater than on the right.

  15. Measuring frame angle Positive frame angle (forward tilt) Should be subtracted from caster spec

  16. Measuring Caster

  17. Camber/Caster Gauges

  18. Caster Shims

  19. Checking Steer Axle Twist Compare left to the right

  20. Camber

  21. Kingpin Inclination

  22. CAUTION: Recheck the toe setting after any change in caster or camber angle.

  23. Turning Angle or Radius

  24. Shop Talk The power steering gear pressure relief valve should open just before the steering stop screw contacts the axle stop. You may have to adjust the power steering gear so that power-assist stops approximately 1 degree before the steering stops contact. Failure to do this will result in slamming of the steering stops on full lock turns.

  25. ACKERMAN GEOMETRY Intersect at the same point, not parallel

  26. In a toe-out condition on turns, the inside wheel turns at a greater angle than the outside wheel

  27. AXLE ALIGNMENT

  28. Axle Offset

  29. ELECTRONIC ALIGNMENTSYSTEMS

  30. BEAM ALIGNMENT SYSTEMS

  31. SENSOR AND COMPUTER ALIGNMENT SYSTEMS

  32. A Hunter WinAlign display screenshowing an initial analysis of alignment data.

  33. WinAlign automatically calculatesthe correction for the technician.

  34. Trailer Tracking

  35. Trailer Axles

  36. INSPECTION PROCEDURE When a steering problem is reported, systematically inspect the vehicle steering system, front and rear suspensions, and trailer suspension. In most cases, a road test will be required, but never take a truck out onto a road until you are sure it is roadworthy. If a reported problem occurs only when the vehicle is loaded, you should test drive the vehicle loaded.

  37. WARNING: When a vehicle is operated at temperatures below 30°F (−1°C) with SAE 90 weight oil in a manual steering gear, it can turn to a grease-like consistency, resulting in stiff, sluggish steering. This can compromise accident avoidance maneuvers because of slow steering response. When operating in temperatures continuously below 30°F (−1°C), install a lighter oil in manual steering gear, such as SAE 75 weight oil.

  38. WARNING: All steering mechanisms are critical safety items. A vehicle should be deadlined (out-of-service [OOS] report) when a defect is reported. It is essential that instructions in the service literature are adhered to. Failure to observe these procedures may cause loss of steering with life threatening results.

  39. Steering Knuckle Vertical Play. 0.04” max

  40. Kingpin Upper Bushing Free Play. 0.015” max

  41. Kingpin Lower Bushing Free Play. 0.015” max

  42. Kingpin Upper Bushing Torque Deflection. 0.015” max

  43. Tie-Rod Inspection

  44. Shop Talk Tighten the nut to the minimum torque first and then continue tightening to align the cotter pin hole. Verify that the torque does not exceed the maximum specification. If it does, replace the nut.

  45. Wheel Bearing Inspection

  46. Adjusting Knuckle Vertical Play

  47. Steering Knuckle Disassembly

  48. Kingpin Removal

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