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How to replace a Defender rear crossmember - pictures

by: Auto Express team

27 Sep 2017

Go to: How to replace a Defender rear crossmember

Rear-mounted fuel tank has to be removed, so run tank low before starting work, then drain or pump fuel out (see this month’s Product Test).
Bolts holding the fuel tank’s support plate to the chassis leg brackets are removed. But they are well rusted to their captive nuts and several shear off.
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Similarly, some of the anti-roll bar mounts have seized bolts. It’s quicker to let them shear off and renew them, and their captive nuts, later.
Two of the fuel tank support plate bolts are accessed through holes in the crossmember. Again, threads and bolt heads are corroded badly…
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..meaning the correct socket won’t fit. James, IRB’s fabricator, used a special tapered socket after cutting part of the scrap crossmember away for access.
The screws holding the body to the crossmember need a prior soak with releasing fluid. Some have captive nuts; those at the ends have free nuts.
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After disconnecting the fuel pipes, cables, and lifting the support plate away, the fuel tank can be worked free from its mounting frame.
Once the tank is out, carefully plug the pipe connections to prevent fuel spillage and store the tank safely, well away from grinding and welding.
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James, who was carrying out the welding for Ian, decided that removing the rear section from the exhaust would significantly improve access.
Body mounting bolts, removed earlier, were temporarily refitted to these two brackets to support the crossmember before cutting it free.
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Disconnect the wiring loom, cut where necessary and pull through with length of wire attached, so you can pull the loom back through when finished.
The new crossmember’s leg length is measured and marked on the chassis. Initial cut leaves extra material, to be trimmed back more accurately later.
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This crossmember was also attached to the chassis at each upper side. James used a power saw, protecting the paintwork with masking tape.
It looks as if the crossmember simply lifted away but it didn’t! There will almost inevitably be small areas of steel still attached. You have to patiently…
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…locate them while working the crossmember up and down when loose, to identify the culprits before cutting through and removing the crossmember.
It’s essential to cut back to sound steel. Ian checked the condition of the metal near the cuts before the repair section was offered up as a trial fit.
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The cut edges are trimmed, and the chassis area where the new section will fit is cleaned up with the grinder to produce a rust-free surface for welding.
The stubs on this repair section had the same dimensions as the original chassis rail, so were tapped outwards enabling it to slide over the chassis.
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It can be tricky to line things up correctly to start with, but it’s important not to panic and to check carefully and methodically as you proceed.
It’s okay to tap the crossmember into position using a hammer, but use a protective piece of wood placed right across the height to avoid dents.
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Part of making the crossmember fit accurately might involve removing small areas of metal. That’s fine provided you leave enough meat in the sandwich.
You’ll need to look for clues to line up the crossmember accurately. This chassis hole (left) conveniently matched one on the repair section (right).
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The joint area can now be marked out accurately with the new crossmember offered in place. Then use the cutting disc to remove the surplus.
At this stage, where bolts sheared during dismantling, the captive nuts were ground off and new nuts (temporarily held with a bolt) were welded in place.
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Finally, after painstakingly ensuring a correct fit – Ian was satisfied that the new IRB crossmember could be located perfectly in position for welding.
The bracket assembly for attaching the crossmember to the body is bolted on separately to provide adjustment, allowing for typical bodywork variations.
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Spend as long as needed, after fitting to the body, in correctly aligning the repair section. Clamp in place, apply a couple of spot welds, then check again.
ames temporarily tack-welded the joint at one side, then the other, continually checking alignments. Tacks can be ground off for readjustment if needed.
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<div> When the new section was securely held by tack welds and correctly aligned, James made complete, unbroken strong welds all the way around the joints. </div>
James used a soft pad on the grinder to clean off any weld spatter and any high spots – it can be tricky welding in such an awkward location.
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With welding complete, the finished job is a treat to behold. New steel welded skilfully to good, clean original steel has produced a strong and long-lasting job.
Owner Phil was full of admiration for the structural improvement to his Defender, and was ready to hitch up his trailer loaded with racing rowing boats.
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