# Box Truck A box truck body is a post and rail structure with a skin over it, mounted on a chassis through a subframe. Dock contacts damage the rear frame and the door, and roof and front radius leaks wet cargo long before anybody finds the entry point. ## What a box actually is, from the inside out A dry van body is a frame with a skin on it. Vertical posts sit on a floor structure of crossmembers, roof bows span the top, and horizontal rails tie the posts together at the bottom and at the top. Over that goes the skin: sheet aluminium riveted to the posts on older and cheaper bodies, fibreglass reinforced panel bonded to the posts on many current ones, or a translucent roof panel bonded at the perimeter. The floor is usually hardwood on steel or aluminium crossmembers, and it carries every load the body will ever see. Knowing which of those you have decides the repair method entirely. A riveted aluminium panel is replaced in a section and re-riveted, which is straightforward. A bonded fibreglass panel is a structural bond repair or a panel replacement, and it cannot be riveted back together without changing how the body carries load. Box and cargo body repair runs $750 to $15,000, five to eighty hours, and the spread reflects that difference more than it reflects the size of the damage. ## The dock is what damages most of these trucks Nearly all box truck body damage happens at low speed in reverse against a fixed object. A dock bumper takes the hit if the truck is square and the dock is the right height. When it is not, the rear frame takes it: the rear header, the corner posts, the sill, and the roll up door track that is fastened to all three. Damage there rarely looks severe from ten feet away and it is structural, because the rear frame is what holds the box square at the open end. The tell is the door. A rear frame that has been pushed out of square puts the door track out of parallel, and the panel then binds at the same point in its travel every time. Operators live with that for months and blame the door. Measuring the opening diagonally in both directions, and comparing, takes two minutes and settles it. Roll up and swing door service runs $400 to $4,500, and squaring the frame first is the difference between a repair and an annual repair. ## Where water gets in, and why the cargo finds it first Two places account for most water in a dry van. The first is the roof to front panel radius, which is the tightest curve on the body and the joint that flexes most, sealed with a bead and covered by a trim. The second is the roof seam along each side where the roof panel meets the top rail. Neither is visible from the ground, and water entering either one runs along a roof bow before it drops, so the stain inside is never under the leak. The consequence for an operator is that the first evidence is damaged cargo, which is a claim of a different kind. Finding the entry point properly means a hose test with somebody inside in the dark watching for light and for water, working one section at a time from the bottom up. Enclosed body roof reseal and repair runs $400 to $4,500, two to eighteen hours. Sealing the whole roof because the source is unknown costs more and often misses the actual joint. ## A lift gate loads the rear of the body every single cycle A lift gate is bolted or welded to the rear of the chassis and the body, and it applies a cantilever load every time it lifts. A gate rated at a couple of thousand pounds is applying that load through a mounting frame several feet behind the rear axle, hundreds of times a week. Mounting frames crack at the weld toe where they meet the chassis rail, and the rear body sill above them distorts. That is normal wear on a hard working truck, not a defect, and it needs inspecting rather than waiting for. Lift gate install and repair runs $1,500 to $8,500, eight to thirty five hours, covering Maxon, Tommy Gate and Anthony among others. What matters on a repair is whether the mounting frame is being restored to the original geometry or simply rewelded where it cracked. We measure the gate platform for level and square against the body before and after, because a gate that sits a degree off level will load one side of its frame preferentially and crack there again. ## The subframe between the chassis and the box A box body does not bolt directly to chassis rails. It sits on a subframe, usually longitudinal timbers or steel sections, fastened with brackets that allow a controlled amount of movement between a flexing chassis and a box that is much stiffer. Those brackets and their fasteners are a wear item nobody inspects. When they loosen, the box moves on the chassis, which wears the rail, elongates the holes, and eventually cracks a bracket. The symptom is a rattle, a box that appears to sit crooked, or a growing gap behind the cab. Chasing it means getting under the truck and checking every mount, then correcting geometry before retorquing anything, because a bracket tightened onto a box that has shifted holds the shift. Frame and structural welding runs $750 to $20,000. On a body that has moved far enough to score a chassis rail, the rail repair is part of the job rather than a separate conversation later. --- Source: https://ocrv.guru/vehicles/commercial-trucks/box-truck/ OCRV Center, 23281 La Palma Ave, Yorba Linda, CA 92887. (949) 799-3387. Serving Laguna Niguel, California. All work performed in shop. No mobile or roadside service. Licences: California Bureau of Automotive Repair ARD00288521; EPA CAL000367879. Published ranges are ranges, not quotes. 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