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In good working order

Now is the best time to catch up on trailer and body maintenance



Now is the best time to catch up on trailer and bodymaintenance

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The current slowdown in freight may give some fleets theopportunity to make sure trailers are in good working order. We asked truck andtrailer OEs to provide some maintenance and repair suggestions. 

The basics

National Semi-Trailer Corp. has put together the followingbasic checklist of items that need to be scheduled for maintenance and repairof trailer dry vans and bodies:

1. Floors and cross members: Minor scrapes and gouges in thefloor are not a concern, however if gouges 1/2-in. or more are noted, fill themwith crack filler or a floor restorer kit. Floorboards can be sectioned as longas the section covers a minimum of three cross members the full width of theboard. Metal plating is not acceptable. Cross members can be straightened aslong as the flange is not pulled away from the floor. Cross members that arepulled away from the floor, cut, torn, or deflected (bowed downward) more than1/4-in. must be replaced. When replacing cross members, end clips must bewelded and Mylar tape must be used between any dissimilar metals.

2. Roofs and roof bows: Roof patches are acceptable as longas the patches are no more than 3-ft. square and are buck riveted with softbuck rivets. If the hole will require a patch larger than 3-ft. square or therewill be more than two patches in a 6-ft. length of roof, the roof must besectioned. A section must start from the front or rear on the trailer, be lessthan 50% of the length of the trailer, and only one section per trailer. Ifthese conditions cannot be met, the roof must be replaced. Only buck rivetswill be accepted; no pull rivets of any kind. Roof bows must be straightened totheir original shape and be free of cuts, otherwise they must be replaced.


3. Body panels and posts: Holes in side panels must berepaired by sectioning the complete width of the panel and buck riveting withhard buck rivets. A section must start from the top or bottom of the panel, beless than 50% of the panel, and only one section per panel. If these conditionscannot be met, the panel must be replaced. Caulking or sealant should be putbetween the panel pieces prior to assembly, not bordering around the sectionafter assembly. Only buck rivets will be accepted; no pull rivets of any kind.Posts must be straightened to their original shape and be free of cuts,otherwise they must be replaced.

4. Rails: Rail sections are acceptable as long as the sectionstarts from the front or rear of the trailer. Only one section per rail isallowed; sections on opposing rails or two rails on the same side are notallowed. If two rails are sectioned the section must be staggered at least 6ft. All sections must be reinforced. Bottom rail reinforcements must be atleast 4-in. x 1/8-in. flat stock iron extending three cross members on eachside of the splice. Top rail reinforcements must be at least 3-in. x 3/16-in.flat stock aluminum extending 18-in. on each side of the splice. Dents andbends in rails should be straightened. If the rail has been bent 1/2-in. ormore in either direction it must also be reinforced. Reinforcements must be atleast 4-in. x 1/8-in. flat stock iron extending two cross members beyond each sideof the damaged area. Mylar tape must be used between any dissimilar metals.Body panel, post and rail damage on trailers less than one year old may berequired to be returned to like-new condition.


5. Doors: Door molding must be repaired if it is cut, broken,if the door core is exposed, or if the door does not fully seal. Door moldingcan be sectioned as long as the door core is watertight and the splice fullyseals when the door is closed. Minor cuts less than 2-in. in the door skin canbe sealed with white Silaprene. Any damage where the door core is broken or isno longer watertight necessitates door replacement. No door sections will beaccepted.

6. Plywood and scuff: Plywood lining with holes or cutslarger than 3-in. or that expose a post must be replaced. The full sheet mustbe replaced with AC grade plywood. Smallcuts and holes smaller than 3-in. where the post is not exposed can be filledwith fiberglass reinforced Bondo. No other patching material like foam, regularBondo, tapes, or wood filler will be accepted. If any plywood has been filledwith an unacceptable patching material, the full sheet must be replaced, notrefilled. Scuff must be full attached with no sharp edges. Broken oak scuffmust be replaced. Scuff may be sectioned with the same type scuff as long assteel splices are welded and oak splices are butt jointed on a post.

7. Landing support gear: Bent or damaged legs need to bereplaced with the same type of leg. Minor bends in braces can be straightened;however, braces that have a kink must be replaced. Wing and support plates mustbe welded to the cross members.


8. Undercarriage and mud flaps: All suspension areas must bestraightened or replaced as necessary to be in good working order. Axles mustbe replaced if they are bent or have spindle damage or grooves. No spindles areto be replaced. Worn bushings must be replaced. Bent mud flap brackets must bestraightened or replaced. Mud flaps with tears, cuts, holes, or cracks must bereplaced with DOT approved flaps.

9. ICC bumpers and rear underride guards: Minor bends may bestraightened. Any other damaged pieces must be replaced. All replacement partsshould be primed and painted to match. (On 1998 and newer trailers, all repairsand replacements must meet federal criteria including a decal showing such.)

10. Lights: The same quality lights and reflectors must bepresent and in good working order.

11. Decal removal: When removing decals, all damageresulting from their removal should be repaired.

12. Tires: Replacement tires should be of the same quality,design and tread depth to the tires at the initial outbound inspection. If afirst line tire is replaced with a retreaded tire, a fee to recover the casingvalue may apply. Tires should be replaced between 2/32-in. and 4/32-in. of treadremaining. If tires are run below 2/32-in. of tread remaining, a fee to recoverany damage to the casing may apply.


13. Brakes: Replacement brakes should be of the same qualitymaterial and design to the brakes at the initial outbound inspection. Brakesshould be replaced when there is between 25% and 30% (measurements of 14/ 15/32-in.) of brake lining remaining. If brakes are run below 25% padremaining, damage from exposed brake shoe rivets may occur, and a fee torecover damage to the brake drum may apply. Notify your local NationalSemi-Trailer Corp. branch office when brakes are approaching 30% (measurementof 14/32-in. to 15/32-in.) of brake lining remaining to schedule a brake job.

Beyond the basics

The engineers at Great Dane offer additional basicmaintenance suggestions. Fleets need to regularly perform wheel-end lubechecks, mechanical fastener torque to specification and do periodic axlealignment checks. In addition, the trailer maker suggests thorough cleaning ofequipment, especially the understructure to remove ice, snow and de-icingchemicals (such as magnesium and calcium chlorides) with low-pressure warmwater wash and rinse.

Also on the company’s list of maintenance tips:

• Check to assure that components used to ingress and egresstrailers are inspected frequently and maintained in a sound and safe condition.

• Maintain all gaskets and seals around doors, vents, andreefer units to assure water- and airtight operations.

• Inspect attaching welds connecting suspensions, upper siderails, landing gear mounts, pintle hooks and impact guards, etc., to bodymembers to assure against fatigue cracks and repair when and if required.


Great Dane goes on to say that there are several maintenanceareas that are typically overlooked and suggest that fleets put these on theirlist as well:

1. Winter weather maintenance and cleaning

2. Tire pressure maintenance when trailers are not equippedwith inflation systems

3. Wheel end lubricant checks

4. Mechanical fastener torque

5. Maintenance of gaskets to seals

6. Attaching welds and their timely repair

Chris Dutton, marketing communications manager for HeilEnvironmental, is a strong advocate for continual comprehensive preventativemaintenance. He says Heil provides, with every vehicle, a chart that outlinesan easy-to-understand preventative maintenance schedule, which includeseverything from checking hydraulic fluid levels to ensuring cotter pins aresecurely in place.

He goes on to say, “Heil firmly believes diligentlyfollowing regular maintenance schedules, as well as insuring maintenance staffare properly trained, is the easiest and most cost-effective way for a fleetmanager to maximize the up-time of their vehicles. Heil Environmental has goneso far as to create a Heil Training Institute, where fleet managers can sendpersonnel to be trained on the most current, cost-effective ways to keep theirRCV bodies in proper working condition, Dutton stated.

Handling corrosion

Figuring out how to protect and repair equipment that issubject to corrosion is a challenge. Heil’s Dutton says, “Exposure to theelements, in combination with the complex array of materials handled every dayby a refuse collection fleet, make corrosion a constant concern for both fleetmanagers, as well as Heil Engineers. One of the best and most proactive ways tohelp minimize the effects of corrosion on any Heil vehicle is an entrenched,regular cleaning schedule for all RCVs. Cleaning the vehicle not only reducesthe effects of any corrosive material that may have become attached to thevehicle body, but also it allows for easy identification and early treatment ofany spots where corrosion may become an issue.”


Great Dane engineers say there are new trends anddevelopments for combating corrosion issues like:

1. Stainless steel trailers, Galvanneal and galvanizedcomponents to combat corrosion

2. Interior liners and scuffs, which are less susceptible todamage due to their higher puncture-resistance, such as Great Dane’s exclusiveSSL and PunctureGuard liners and scuffs

3. Long-life return-ground, sealed lighting systems

4. Pre-set wheel ends offer low or no maintenance forextended periods

5. Tire inflation systems

6. Super single tires and wheels

Rear frames and doors pose the biggest problem area forcorrosion on trailers, most doors on dry-freight trailers are plymetalconstruction with plywood cores and metal skins, says Wabash National Corp.Chief Technology Officer, Rod Ehrlich. “The wood acts like an ink blotter andabsorbs moisture through any leak, even the smallest hole. The skin is alsopart of the problem because it is a chilling agent, and as the temperaturecools, a vacuum is created, and the door draws in moisture, which travelsthroughout the core. This process also is impacted by gravity, which is why wesee the worst galvanic corrosion at the bottom of the door.”

To prevent this occurrence, according to Ehrlich, Wabashhas eliminated plywood from its rear doors, which are now made out of DuraPlateas are the composite sidewalls. The material does not absorb moisture and hasthe added benefit of allowing door seals to be screwed in place. By contrast,fasteners on wood core doors can act as moisture conduits and are oftendestroyed by corrosion from the inside. For rear frames, Wabash has elected touse a thermoplastic powder coating that adheres to the steel, which evaluationshave shown provides as much as seven times the corrosion resistance.


FRP repairs

The Technology and Maintenance Council offers detailedinstructions for repairing fiberglass reinforced plastic (FRP) van trailers andbodies in its recommended practice RP 725. Of special note are the guidelinesfor preparation, which cautions fleets to always check for hidden damage, whichcan cause delamination of the fiberglass woven roving from the plywood core.

Delamination is not always visible, but can be detected bytapping the panel with a metal object, such as a coin, around the visibledamage. A solid sound indicates the panel has maintained its integrity; dullmuffled sound suggests hidden delamination. If a dull sound occurs, check theother side of the panel.

If an FPR repair is needed, be sure to check the coremoisture level of the panel. If the core is moist, a low heat glow dryer or aheat lamp may be used to expedite drying. Always roughen the surface and removeglossy finish before bonding or painting over the FRP surface.

For more information, visit

Bringing up the rear

Don’t forget to check the rear impact guards. Make their inspection routine. FMVSS 223 and224 regulate the strength, location and energy absorption and dimensions ofrear impact guards. Certification labels or plates are required to be visibleon the forward facing surface of the horizontal member and located within 12in. of the outside of the horizontal member on the curbside of the unit.


For more information, visit

If fleet equipment is outfitted with liftgates, regularlyschedule inspection and maintenance. Make sure drivers report problemspromptly. Do visual inspections to check for oil leaks, uneven ramps orplatforms, missing parts, compromised weld or cracking. Always check themechanical operation to make sure the liftgate is functioning properly duringraising and lowering. Check the pump/motor and wiring and/or switches. Makesure all safety devices are working properly.   

Reefer unit maintenance

For PMs, Thermo King Corp. has a detailed list of items to check on units and trailers. Here is just a short list toconsider:

Unit examination

• Place all unit switches in the Off position.

• Check unit doors – open, close and latch properly.

• Check defrost drain hoses and flapper valves.

• Check for coolant leaks.

• Check for oil and fuel leaks.

• Reset/Check engine air restriction indicator.

• Check for loose, frayed, or chaffed wiring.

• Visual check of drive belts.

• Check reset switch circuit in Continuous Run.

• Check coolant level.

• Check battery cable connections.

• Check battery hold-downs.

• Check for proper engine oil level.

Inside trailer

• Check front bulkhead, floor channels and air chute for airflow restrictions.

Multi-temp units only––check:

• Remote evaporators for damage.

• For damaged, loose/missing hardware.

• Defrost drain hoses and flapper valves.

• Compartment bulk head(s).

For more details, contact your local Thermo King dealer orvisit

5th wheel maintenance ensures the right connection

The proper connection between trailer and tractor startswith proper maintenance of the fifth wheel. The technical experts atSAF-Holland suggest that routine, periodic maintenance and lubrication are anecessary part of fifth wheel service life. To get the maximum performance,follow the steps below at the intervals shown:


A. Thoroughly clean the locking mechanism every 6 months or60,000 miles.

B. Inspect for bent, broken or missing parts every 6 monthsor 60,000 miles. Replace as necessary (use only genuine Holland parts).

C. Re-lube and inspect regularly.

D. Check the operation by locking and unlocking using aHolland lock tester. Verify that the fifth wheel is completely closed.

Basic maintenance is the key to good performance. Alwaysfollow the manufacturer’s recommended procedures for the best success.


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