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Strengthening plates

Strengthening plates

Strengthening plates for the D40 Nissan Navara have been designed to fit inner and outer sides of both chassis rails, integrating with the front tub mounting brackets and right-hand rear shock mount. A plate is also provided to stiffen the underside of the rails.

Chassis access

Chassis access

Getting full access to the chassis requires the rear tub (load bed) to be removed. Start by unbolting and removing the rear bumper. If a towbar is present, disconnect the electrics which are often wired into the rear lights.

 

Lowering the tailgate gives access to two bolts that hold the rear light clusters in place. Take note of wiring colours and location.

Removing the tub

Removing the tub

The rear tub is held onto the chassis with four bolts, using captive nuts. Disconnect the wiring loom plugs under the left-rear corner, and remove the clamp bolt that holds the fuel filler pipe and breather to the tub.

 

Using suitable lifting equipment, ease the tub upwards and rearwards to clear the back of the cab. Note, the fuel filler neck stays behind – keep the fuel filler flap open as you may need to prise the rubber collar away from the tub when starting to lift.

Chassis inspection

Chassis inspection

With the tub removed, a thorough inspection of the chassis can be made, particularly the curved rails behind the cab that incorporate the front tub mounts. Use a small hammer and gently tap around the chassis looking for signs of failure and hidden corrosion. Remove the rear wheels to improve access, supporting the truck on axle stands.

Welding and plate fitting

Welding and plate fitting

Geoff’s chassis revealed slight surface corrosion, and this was removed using an air-powered needle scaler. Wiring was unclipped, then surface coating or corrosion was stripped back to bare metal, in preparation for welding.

 

The plates were test-fitted using clamps. The lower plate was bent and trimmed to follow the curve of the chassis rail, so the side plates could sit on the protruding edges. Notches were cut into the tub mount, to ensure a flush fit.

 

Before any welding, disconnect the battery to avoid damaging vehicle electronics. With the lower plate tacked in place, it could be fully welded before adding the side plates. To manage heat dispersion and limit warping, Adam welded 15mm, leaving a 30mm gap, then worked progressively around each plate to complete the process.

Custom fit and plate modifications

Custom fit and plate modifications

The right-hand chassis rail carries a shock absorber. Its mounting pin was cut free and removed, allowing the inner plate to sit flush, before the pin was re-installed.

 

Do not cut the plate in half and weld around the pin – this short-cut will not be as strong.

 

The right-side outer plate needed modifying to fit correctly. Bevel edges were applied to improve the fit over existing welds, and to allow better access to re-weld the shock absorber mounting pin.

Shock absorber installation

Shock absorber installation

With the plates fully welded, the shock absorber pin and its mount could be correctly installed in its original position. It needed trimming to allow for the thickness of the strengthening plate, to maintain vertical alignment to the rear axle mount.

Painting

Painting

With all fabrication complete, the chassis underwent further cleaning and rust removal, before a coat of red oxide primer was applied by brush. Once dry, a top coat of black paint was applied, before all wiring, rear tub and bumper were refitted.

 

Remember to refit the rubber supports that cushion the tub against the chassis.

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