Direct answer: every unrestored FJ40 rusts in the same nine places — rear quarters and lower corners, rear sill, floors and braces, tailgate skins, fender aprons, firewall footwells, windscreen frame, door bottoms and the channels around body mounts. Toyota never galvanised the 40-Series, and fifty years of mud packed between body and chassis does the rest. Here's how to inspect each area and what fixes it.
1. Rear quarters and lower corners
The rear wheels sandblast and salt the quarters from inside the arch. Bubbling along the lower body line means the metal behind is gone. Fix: corner and quarter pressings, or corner patch panels when rot is confined to the last 150 mm.
2. Rear sill and floor braces
The rear sill collects everything the tub drains. Probe it with a screwdriver from below — paint hides lace. Fix: sill assemblies and floor sections, replaced together with braces in one operation.
3. Floor pans
Rot starts under mats where condensation sat, and over outriggers where mud packed. Lift carpets, check seat and belt anchor areas — they're structural. Fix: front and rear floor pressings, plug-welded at factory spacing with reinforcements per the original layout.
4. Tailgate skins
Double-skinned gates trap water; they rot from inside out along the bottom hem. Fix: complete reproduction tailgates — skinning a rotten frame is false economy.
5. Front fender aprons
Mud packs behind the headlight bowl and against the apron. Bubbles around the light mean the apron is worse. Fix: front fenders bolt on; aprons and inner structures are welded pressings.
6. Firewall footwells
The cowl plenum drains leaves and water straight onto the footwell corners. Check under dash pads and around pedal boxes. Fix: firewall sections — drive-side specific, so order LHD or RHD.
7. Windscreen frame
Hardened seals let water sit in the fold. Check the lower corners inside and out.
8. Door bottoms
Blocked drains rot the bottom hem. Fix: door patch sets for sound frames, complete doors when the frame has gone.
9. Body mounts
Every mount channel traps mud against bare steel. With the body off — or a mirror and a light — check each one; new tubs on rotten mounts is money wasted.
The honest assessment
Count the areas that need steel. One to three: panel repairs. Four to six: price panels + labour against a tub or cab assembly. More: the assembly wins, every time. Either way, buy the right panels once.
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