How One Builder Created His Perfect FJ45 - Starting With an FJ40

Building a custom 4x4 takes serious dedication, but when you see the results, you understand why people pour their hearts into these projects. Zach from Northern California took his 1975 FJ40 and transformed it into something that looks like it rolled off the assembly line as an FJ45 - if Yota had built FJ45s with one-ton axles and 43" tires.

The build started with a vision: create the perfect Sierra Nevada rock crawler that could handle everything from Rubicon trails to desert runs. Zach didn’t just want another modified FJ40. He wanted the extended cab look of an FJ45 with modern capability underneath. The fabrication work he pulled off in his garage is impressive, especially when you consider he cut the factory hardtop in half and sectioned the body to create that extended cab profile.

The foundation of this build sits on serious hardware. Up front, an ‘08 Super Duty axle with 5.38 gears and $1,550 Chromoly shafts handles the grunt work. The Sterling 10.5" rear axle matches that capability with its own set of Chromoly shafts and ARB lockers front and rear. Those 43" Mickey Thompson tires on 17" Sidetrack Offroad beadlocks give this thing a stance that demands respect on any trail.

What really sets this build apart is the attention to detail in the suspension setup. Zach originally ran King 2.0 coilovers but has since upgraded to 2.5s with clickers up front. The 14" travel coilovers and 16" bypasses provide the kind of wheel travel that makes technical terrain feel manageable. The triangulated four-link rear setup and three-link front with the upper link on the passenger side required serious engineering to fit everything in the tight confines of an FJ40 frame.

The LS swap makes perfect sense for this application. The 5.3 LM7 with a Brian Tooley cam and LS7 injectors provides reliable power without the complexity of a built motor. Paired with an NV4500 five-speed and Atlas 4.3:1 transfer case, the drivetrain gives Zach the crawl ratios he needs for technical rock work while still being highway-friendly for those long drives to the trailhead.

The interior work shows Zach’s practical approach to the build. The crazy, custom 53" PRP bench seat might look massive, but it fits the extended cab perfectly and provides comfortable seating for trail adventures. The twin-stick Atlas setup gives precise control over the drivetrain, while the tilting GM column and factory Yota details maintain that classic FJ aesthetic.

Building the rear section from scratch required serious fabrication skills. Instead of trying to source an actual FJ45 bed, Zach built the entire rear body section using square tubing and sheet metal. The result looks factory but provides exactly the proportions he wanted. The custom 26 gallon aluminum fuel tank fits perfectly over the rear axle, maximizing capacity while maintaining ground clearance.

Recent updates to the build show Zach’s commitment to continuous improvement. The switch to trailing arms in the rear and upgraded suspension components came from real-world testing and feedback from experienced builders like Trevor at WFO Concepts. The new 22 gallon fuel cell and ARB fridge setup in the back transform this from a day-wheeler into a serious expedition rig.

The fabrication work extends to every detail. That headache rack isn’t just for looks - it’s built to handle the abuse of serious wheeling while providing mounting points for LED lighting. The side-exit exhaust keeps the pipes protected while maintaining that classic off-road sound. Even the tailgate is hand-built with YJ hinges and proper bead rolling for a professional finish.

What makes this build special isn’t just the capability - it’s the approach. Zach sourced parts smart, buying used axles from friends and hunting deals on Marketplace for components like that old-school aluminum winch. The paint might be a “10 footer” shot in his garage, but it looks great and proves you don’t need a professional booth to get solid results.

The mechanical fan and Griffin radiator setup deserves mention for anyone considering cooling options. While electric fans might seem like the modern choice, the mechanical setup never fails and keeps temps rock-solid even during extended low-speed technical sections. Sometimes the old-school approach just works better.

For anyone considering a similar build, Zach’s approach offers a solid blueprint. Start with a clear vision, source quality components, and don’t be afraid to fabricate what you can’t buy. The results speak for themselves when you see this thing rolling down the trail.

Check out more of Zach’s work and build details at Smokey Mountain Fabrication or follow the progress on Instagram. Sometimes the best builds come from passionate builders working in their own garages with a clear vision of what they want to create.