Chapter 04. Preventive Maintenance Standards for Freight Trailers and Freight Semitrailers

Axles, beams, spindles or mountings which are broken, damaged, worn, rusted, bent, or modified may affect wheel alignment, tracking, or vehicle handling or stability.

Spring and Attachments. Unequal vehicle height, broken or damaged spring leaves, spring shackles, bushings, center bolts, U-bolts, control arms, torsion bars or equalizers can affect vehicle steering, alignment, tracking, handling, and stability. With vehicle on a level surface, inspect:

Torsion Bar. All other suspension components shall be inspected the same as leaf spring suspension.

Coil Springs and Mountings. Visually inspect coil springs, control arms, rear torque arms, axle strut (when equipped), and front and rear stabilizer bar (when equipped).

Rubber Load Cushions. All other suspension components shall be inspected the same as leaf spring suspension.

Tandem Axle Walking Beams.

Sliding Bogie.

Air Suspension (All Axles). Two procedures are required to inspect air suspension systems.

Air Suspension. Inspection is conducted with normal air pressure in suspension system.

Shock Absorbers (if Equipped). Shock absorber inspection includes leakage, mounting, and all related attachments. When originally equipped with shock absorbers, inspect for:

Road Clearance.

Brake Lines and Hoses. Visually inspect:

Vacuum System.

Drum Brakes—Hydraulic.

Disc Brakes—Hydraulic.

Brake Lines and Hoses—Hydraulic.

Air Leakage. Inspection for leakage shall be conducted with a fully charged system and brakes fully applied.

Air Reservoir and Valves.

Parking and Emergency Brake Application. Vehicles with original equipment air-operated parking brakes are permissible. There are different systems designed for automatic or manual operation of the system as the design allows (check automatic application of brakes when air tanks are being drained).

Gladhands and Air System.

Brake Mechanical Components. Do not attempt to dismantle a double diaphragm spring brake unit while it is on the vehicle. Utilize a safety cage and remove the entire unit from the vehicle. Replace with a new or rebuilt assembly. When rebuilding or overhauling a brake chamber, strict adherence to manufacturer's procedures is required. Inspect brake chamber for:

Slack Adjuster (Push Rod) Travel. With the assistance of a second party, apply 85 psi in system and note rod travel.

Wedge Brake. With the assistance of a second party, make a full brake application.

Brake Camshafts.

Brake Linings—Air Brakes. Visually inspect brake shoes. If shoes cannot be seen, removal of the lower portion of the dust cover is required.

Brake Drums—Air Brakes.

Disc Brakes—Air.

Brakes—Electric.

Break Away (Emergency Brake).

Tire Inspection—Nonsteering Axle.

Wheels. Visually inspect:

Rims. Visually inspect for:

Lock Rings.

Studs, Nuts, and Clamps. Inspect for:

Frame.

Frame Cross Members.

Body Mounts.

Floors (if Applicable).

Doors, Handles, Latches, and Hinges.

Landing Gear (if Applicable).

Rear Protector (Mud) Flaps. Rear protector flaps are not required on a vehicle when the construction is such that complete freedom around the wheel

Sheet Metal.

Rear Metal Frame. Each trailer and semitrailer, when operated on the highways, shall be equipped with a permanent metal frame attached to the underside of the rear of the trailer. The frame may not be wider than the width of the trailer and more than 30 inches above the highway, and shall be constructed of heavy gauge steel. The maximum The maximum transverse distance from the widest part of the vehicle at the rear to the frame may not exceed 18 inches. Any trailer or semitrailer so constructed and maintained that the body, chassis, or other parts afford the required protection is in compliance with this regulation. This regulation does not apply to pole trailers or trailers or semitrailers when the installation of the frame would prevent operation of the vehicle in fulfilling its designed use. The frame may not interfere with lights or other warning devices. Inspect rear metal frame for:

Tail Lamps. Inspect tail lamps for:

Stop Lamps. Inspect stop lamps for:

Turn Signal Lamps. Inspect turn signal lamps for:

Hazard Warning Lamps. Inspect hazard warning lamps for:

Side Marker Lamps. Side marker lamps may function as both side marker and clearance lamps. Inspect side marker lamps for:

Clearance Lamps. Clearance lamps are not required on vehicles less than 80 inches in width or on rear of truck tractors. Inspect clearance lamps for:

Identification Lamps. Identification lamps are not required on vehicles less than 80 inches in width. Inspect identification lamps for:

License Plate Lamp or Lamps. Inspect license plate lamp or lamps for:

Additional Lamps (if Equipped).

Reflectors.

Wiring. Visually inspect wiring for:

Upper Fifth Wheel Plate.

Kingpin.

No-Slack Hitch. Apply air pressure to no-slack hitch before inspecting.

Converter Dolly and Fifth Wheel Structure. Inspect:

Trailer Hitches. Inspect hitch for:

Secondary Attachments. Inspect for presence and condition of:

Tanks. Inspect:

Pressure Vessels. Inspect: