Castloc II and Simplex Series

cen mm 31.01.000

Warning: All fifth wheel maintenance, adjustment, and rebuilding must be done only by a qualified mechanic. Improper or incomplete procedures could result in a possible disengagement of the trailer from the tractor, which could result in personal injury or property damage.

Parts are under spring compression. Wear safety goggles while servicing the fifth wheel. Failure to do so can result in personal injury, due to parts ejecting with force.

  1. Disconnect the tractor from the trailer. For instructions, see the vehicle driver's manual.
  2. Thoroughly steam clean the fifth wheel.
  3. Check the fifth wheel plate for cracks. Check for sharp edges on top; the chamfer should be 1/8 to 1/4 inch (3 to 6 mm).
  4. When the wheel is locked, the safety latch must swing free and fall freely into position. See Fig..

    1. Lubricant Grooves

    2. Safety Latch

    3. Lock Control Handle

    4. Mount

    Fig. 1, Simplex Series Fifth Wheel

  5. The lever bar and operating handle must be in proper alignment. See Fig.. Compare the lever bar and operating handle alignment to a new, or a properly operating lever bar and operating handle. Replace any bent or misaligned lever bar or operating rod.

    1. Operating Handle

    2. Lever Bar

    Fig. 2, Lever Bar and Operating Handle Alignment

  6. Check all cotter pins for cracking or damage. Replace any cotter pin that shows any signs of damage.
  7. Level the fifth wheel plate to a horizontal position. Measure the height from a stationary mounting point (see Fig., Ref. 3), such as the frame rail to the top of the fifth wheel plate (Ref. 1). Pry up on the fifth wheel plate (Ref. 4) below the pin boss, and measure the vertical movement (Ref. 5). The bracket connection provides a 9/32-inch (7-mm) vertical clearance to provide cushioning and to avoid downward pin-loading while retaining minimum plate lift. If the plate lift (Ref. A) exceeds 5/16 inch (8 mm) as a result of wear or rubber deterioration, install new, standard or oversized bracket-shoe rubber pads; see of the Century Class Trucks Workshop Manual for replacement instructions.

    • Extended Top Plate Lift Height

    1. Fifth Wheel Top Plate

    2. Fifth Wheel Frame Mount

    3. Frame Rail

    4. Lifting Point

    5. Static Top Plate Height

    Fig. 3, Measuring Fifth Wheel Top Plate Lift

    8. Note: Do not measure plate lift immediately after a trailer has been uncoupled from the fifth wheel. The rubber may have taken a temporary set, which will normally recover after being uncoupled for a short period of time.

  8. Check all mounting bolts for signs of fatigue, and tighten them to the proper torque. For torque specifications, see . Inspect all angles, plates, and brackets for cracks or other damage.
  9. Replace cracked, worn, or damaged parts with new parts. Replace all loose mounting bolts with 5/8–11 SAE grade 8 bolts, grade C locknuts, and hardened washers. Do not re-use bolts, nuts, and washers on fifth wheel mountings.
  10. After inspecting the fifth wheel, lubricate all moving parts with a chassis or multipurpose grease. See Maintanence Operation General Description for lubrication instructions.
Note:
Parent topic: Inspection of the Fifth Wheel
Document Number: 0000122015
Manual Publication Date: 2025-02-11
Topic Publication Date: 2024-06-04