# Fifth Wheel Repair for Eastvale, California > Pin box, upper deck, front cap and large slide repair for fifth wheels towed to the Yorba Linda shop from Eastvale. Source: https://ocrv.info/vehicles/campers-and-trailers/fifth-wheel A fifth wheel tows from a hitch in the truck bed through a kingpin mounted in a pin box under the raised forward section. Repair work involves pin box and upper deck structure, front cap water intrusion, large slide rooms, landing gear, hydraulic leveling, tall sidewalls and residential grade interior components. ## Pricing Typical range $750 to $50,000+, 5 to 250 hours. The forward section of a fifth wheel is where most of the interesting engineering and most of the expensive problems live. The upper deck holds the bedroom, sits above the truck bed, and transfers the entire hitch load through the pin box into the frame. That load path passes through a section of the body that also happens to contain a big front cap, several windows and, on many units, a front cap seam that faces directly into the weather at highway speed. Kingpin and pin box condition is the first thing checked on any fifth wheel that arrives with a complaint about towing behavior. Pin boxes wear at the bushing, mounting bolts elongate their holes, and the frame section behind the box can crack at the weld where the upper deck steps down to the main rails. None of that is visible from the ground with the trailer hitched, which is why the inspection puts the unit on jacks with the pin box accessible. Fifth wheels are also the largest towables on the road, with slide rooms that can run the length of the living area and dry weights that push what a heavy duty truck can pull. Owners in Eastvale tow them roughly twenty miles down SR-71 and SR-91 to the Yorba Linda facility. The building takes them indoors, which matters for roof work, refinishing and any repair where the interior is opened. ## Common damage - Cracked frame at the upper deck step - Worn pin box bushings and elongated bolt holes - Front cap seam leaks into the bedroom floor - Slide room out of square with partial seal contact - Landing gear gearbox failure and bent legs - Front window frame leaks on the upper deck - Roof membrane damage above the front cap ## Pin box, upper deck and frame Every pound of hitch weight passes through the pin box, into a mounting plate, and then into the frame rails that step up to form the upper deck. The step in the frame is a stress concentration by geometry, and manufacturers vary in how well they reinforce it. Cracking at that transition shows up as a hairline in the paint on the rail web, a squeak that appears when hitching, or in bad cases a visible sag at the front of the trailer with the landing gear down. Repair follows a sequence. The area gets cleaned and inspected with the load off, cracks get drilled at the tip to stop propagation, the weld is ground out and rebuilt with correct preparation, and a doubler or gusset gets designed in where the original section was undersized. Pin box mounting holes that have elongated get repaired rather than filled with a larger bolt. The whole assembly gets rechecked with the trailer loaded before it leaves. - Frame step transition inspected with the load removed - Crack tips drilled before grinding and re welding - Gussets sized to the actual section, not guessed - Elongated pin box mounting holes properly repaired - Landing gear mounts and gearbox checked at the same time ## Front caps, upper deck leaks and the bedroom floor The front cap on a fifth wheel is a large fiberglass molding with a seam at each side where it meets the sidewall, plus windows and often an exterior storage door. At tow speed that cap acts as the leading face of the vehicle, so any opening in the seam gets pressurized water forced into it every time the unit is towed in rain. The result is a wet upper deck floor that the owner finds as a soft spot beside the bed months later. Repair works from the inside out. The bedroom floor covering and base cabinetry come up, the extent of wet subfloor gets mapped, and the wall base is opened where moisture traveled. Rotted subfloor is cut out and replaced, wall framing is repaired, then the cap seam is stripped completely and rebuilt with the correct sealant on clean substrate. Rebedding the seam without addressing the floor leaves the owner with a dry leak and a rotten floor. ## Big slides, leveling and residential interiors Living room slides on a fifth wheel can be eighteen feet long and carry a full sofa, a dinette and a section of flooring. That much cantilevered weight makes squareness critical. Symptoms of a room that has gone out of square include a seal that only contacts along part of its length, flooring that catches on the wall as the room comes in, and a mechanism that draws more current on one side. Diagonal measurements and a level reading at the outboard edge come before any parts discussion. Hydraulic auto leveling systems interact with all of this. A trailer levelled on jacks with the frame twisted will bind every room on the unit, and owners who level on uneven ground repeatedly can induce permanent set in the body. Leveling components, mounts and the structure they attach to are all serviceable here. Residential refrigerators, fireplaces, washer and dryer installations and solid surface counters get handled as part of interior work. - Diagonal and level measurements before mechanism diagnosis - Seal contact checked along the full room perimeter - Leveling jack mounts and frame attachment inspected - Flooring transition at the room edge corrected - Residential appliance and counter work handled in shop ## Frequently asked questions ### My fifth wheel sags at the front when the landing gear is down. What is that? That is a structural symptom and it needs measurement rather than adjustment. The likely causes are cracking at the frame step below the upper deck, fatigue at the landing gear mounts, or a main rail that has taken a set from repeated overloading. The inspection puts the unit on stands, removes the load and examines the rail webs and welds directly. ### Why is my bedroom floor soft when the roof does not leak? Because the water is coming in at the front cap seam or a front window rather than from above. At tow speed the cap face is pressurized, and any gap in the seam forces water into the wall cavity where it runs down to the upper deck floor. The floor gets wet from the edges inward, which is why the middle of the room can feel solid while the perimeter is rotten. ### Can a long living room slide be repaired without removing it? Seal replacement, mechanism service and flooring transition work all happen with the room in place. Structural repair to the room frame, floor deflection correction or wall repair at the opening generally requires the room to come out. Whether removal is needed becomes clear once the squareness measurements are taken, and the estimate states which path is being priced. ### Is hitch related damage covered as a collision claim? Frequently yes, particularly when a hitch failure, an unhitching incident or a bed rail contact caused the damage. Documentation matters. Photographs of the pin box, the frame transition, the truck bed contact points and any deformation go into the file. Collision estimates carry no charge and open claims are handled at the Yorba Linda facility. --- OCRV Center. 23281 La Palma Ave, Yorba Linda, CA 92887. (949) 799-3387. info@ocrvcenter.com. Serving Eastvale, California in Riverside County, about 20 miles from the shop. All work is performed in shop at the Yorba Linda facility. No mobile, roadside or on-site service is offered. Scope is body, paint, structural, fiberglass, interior and vehicle systems work. Engine rebuilds, transmission rebuilds, drivetrain work, DOT inspections and emission testing are not performed.