ConMet Simplex®

m2+ m 31.02.000
  1. Disconnect the tractor from the trailer. For instructions, see  of the Business Class M2 Plus 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.. 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 clinch pins for cracking or damage. Replace any clinch pin that shows signs of damage.
  7. Measure the top plate lift. See Fig..

    • 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

    1. Level the fifth wheel plate to a horizontal position.
    2. Measure the height from a stationary mounting point, such as the frame rail to the top of the fifth wheel plate.
    3. Pry up on the fifth wheel plate below the pin boss, and measure the vertical movement.

      Note: 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.
      1. If the plate lift exceeds 5/16 inch (8 mm) as a result of wear or rubber deterioration, install new, standard or oversized bracket-shoe rubber pads; see the Simplex Fifth Wheel Operating and Maintenance Manual for replacement instructions.

      4. 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.

    4. Check the clearance between the kingpin and the jaw of the fifth wheel. If the clearance is greater than 1/8 inch (3 mm), dial out the slack using the eccentric jaw pin. For detailed instructions, see the Simplex Fifth Wheel Operating and Maintenance Manual .
    5. Check all mounting bolts for signs of fatigue, and tighten them to the proper torque. For torque specifications, see  in the Business Class M2 Plus Workshop Manual. Inspect all angles, plates, and brackets for cracks or other damage.
    6. 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.
    7. After inspecting the fifth wheel, lubricate all moving parts with a chassis or multipurpose grease. See  in the Business Class M2 Plus Workshop Manual for lubrication instructions.
    Note:
    Parent topic: Fifth Wheel Inspecting
    Document Number: 0000120380
    Manual Publication Date: 2025-02-11
    Topic Publication Date: 2024-06-05