Daily Driven Monster: Inside the V8 Tundra Supercharged 4Runner on 40s

When you first lay eyes on Jason’s RSG T40R, your brain takes a second to process what you’re seeing. A 5th gen 4Runner sitting on 40-inch Toyos should look awkward, but this rig looks like it rolled off some alternate-universe Toyota assembly line where engineers decided to build the ultimate trail weapon from day one.

Jason from RSG Offroad didn’t mess around when he started this build back in 2016. He bought a brand-new 5th gen with less than 5,000 miles specifically to cut it up. Most folks would call that crazy, but Jason had a clear mission - build something that could hang with a Jeep JK on 40s while keeping all the reliability and comfort Toyota is known for.

The transformation starts underneath where Jason completely ditched the factory IFS setup for a proper solid axle. Up front sits a Ford high-pinion 9-inch in a Spider Tracks housing with 5.13 gears and an ARB locker. The rear gets a Curry axle housing also running a Ford 9-inch, sized to Tacoma width for perfect stance matching. Both ends roll on Trail Gear beadlocks wrapped in 40x13.50R17 Toyo MTs.

What makes this build special isn’t just the axle swap - it’s how Jason retained every factory feature. The truck still has ABS, electronic four-wheel drive, and even crawl control. He machined factory reluctor rings onto the Trail Gear outer hubs to keep the ABS system happy. No warning lights, no compromises.

The suspension setup uses custom King 12-inch coilovers at all four corners with 2.0 hydraulic bump stops. Jason had to raise the engine an inch and a half to clear everything up front. Out back, he went with a reverse triangulated four-link setup - something most builders avoid because of driveshaft angles, but it works perfectly for this application.

Under the hood is where things get really wild. Jason swapped in a complete 5.7-liter Tundra V8 with a Magnuson supercharger pushing around 600 horsepower. The entire Tundra ECU, harness, transmission, and transfer case got spliced into the 4Runner’s electrical system. Everything from power windows to door locks works exactly like factory.

The exhaust system features Doug Thorley headers flowing into a 3-inch custom system with no cats. Jason says it “rumbles pretty good” - probably an understatement for a supercharged V8 in a 4Runner body.

Steering gets help from a full Howe hydraulic assist setup. Jason can steer this thing at a dead stop with his pinky when it’s in four-wheel drive. The system includes a Howe box and hydraulic ram that makes maneuvering those 40s effortless on the rocks.

The interior features a custom dash with an iPad integration and full digital audio system. There’s even a 360-degree camera system that automatically switches views based on your turn signals. When you’re piloting something this wide, being able to see around corners becomes pretty important.

RSG’s armor protection includes their bulletproof rock sliders - the ones they actually tested on this truck before bringing them to market. The front bumper is a custom RSG piece that might see production someday, while the rear bumper replaced the factory frame crossmember entirely. Jason cut out the original and welded this one directly into the frame rails.

The build took serious commitment. Jason estimates just over $100,000 invested including the base vehicle, and that’s mostly parts costs. Labor would push that number much higher if you were paying someone else to build it.

What’s impressive is how Jason uses this rig. It’s not a garage queen or show truck - he daily drives it and wheels it hard. The body damage tells the story of someone who built this thing to use it. You can cruise at 70-80 mph on the highway in eco mode, then hit the gnarliest trails without breaking a sweat.

The attention to detail separates this build from typical solid axle swaps. Most builders cut corners and end up with warning lights, systems that don’t work, or missing features. Jason made sure everything functioned properly before even starting the build, laying out wheel bearing components on the ground with a multimeter to verify his theories would work in practice.

Jason kept the build under wraps for years, just enjoying driving it instead of chasing publicity. But eventually, the unicorn status got to him. Too many people thought it was fake or photoshopped, so he started showing it off to prove this wild creation actually exists.

The RSG T40R proves you don’t have to choose between capability and comfort. Jason wanted something that could out-wheel his Rubicon while staying reliable and comfortable for daily driving. Mission accomplished. This thing represents the ultimate evolution of what a 4Runner could be with unlimited budget and serious fabrication skills.

You can follow the build and see more of this beast in action on Instagram @rsg_t40r or check out RSG’s other projects at rsgoffroad.com.