If you have a D40 Nissan Navara (2005-2015) that has not yet succumbed to the dreaded chassis rot, it could be worth fitting strengthening plates to the area most susceptible, behind the cab. Geoff Ashcroft gets first-hand experience.
Nissan’s D40 Navara chassis failures have become well documented in recent years. Models affected are those with a VSK chassis number, and a prolonged period of goodwill and buy-backs from Nissan now appears to have drawn to a close.
The area of main concern is with both chassis rails, between the back of the cab and the front part of the load bed. Corrosion gets hold of the structure, often from inside-out, and it is an MoT failure at best, and a road safety concern at worse.
Exceeding design weights and towing capacities in-service, can accelerate the issue through increased chassis flex.
So what can you do to keep your D40’s chassis in good health? A social media page titled ‘Nissan Navara snapped chassis group (05-15)’ has evolved with a wealth of information, including tales of woe and also those of hope and inspiration.
A galvanised chassis swap is available through Yorkshire-based Thornton Breakers, at a cost of £3,000, though a more cost-effective solution is to fit chassis strengthening plates to maintain the integrity of a non-suffering D40. These are available through the Facebook group for £75. It is a route our very own 4x4 correspondent took, Geoff Ashcroft, having recently purchased a solid 2011 Navara V6 Outlaw model, at a favourable price.
A thorough inspection revealed no issues with his Navara’s chassis, so he enlisted the services of welder-fabricator Adam Coomber of Ettington, Warwickshire-based JLA Fabrications to carry out the strengthening work.
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.
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.
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.
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.
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.
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.