Tech Spotlight: Traxxas Extreme Heavy Duty 4X4 Upgrade Kit
Transform Your 4X4 with a Full Package of Battle-Ready Accessories
The Hoss 4X4, Slash 4X4, and Rustler 4X4 are some of the toughest RTR trucks ever to set their tires into dirt, but Traxxas knows some of you like to go even faster, hit harder, and fly higher with your 4X4 machines. If you’re in that top percentile of no-holds-barred “send it!” 4X4 fans, the Extreme Heavy Duty Outer Driveline & Suspension Upgrade Kit is for you. The complete, easy-to-install kit replaces the stock caster blocks, steering blocks, hub carriers, shock towers, and driveshafts with all-new parts engineered for unbeatable strength and to keep your brand high-speed, high-flying fun going nonstop. Let’s take an up-close look at what you get when you give your 4X4 the Extreme Heavy Duty treatment.

The Extreme Heavy Duty Kit has everything you need to convert your Hoss 4X4, Slash 4X4, or Rustler 4X4 for over-the-top durability including bearings, body mounts, steel drive hexes, and fresh hardware.
The Extreme HD kit’s caster blocks, steering blocks, and rear hub carriers are engineered for incredible strength. The shock towers have been revised to work with the Extreme Heavy Duty driveshafts.


You can get the Extreme HD kit in blue, red, green, orange, and black. All the molded parts are also available separately should you need to replace one (or if you want to mix colors).

The kit installs without modification on the Hoss 4X4, Rustler 4X4, and Slash 4X4. The Stampede 4X4 is the only 4X4 model that does not accept the Extreme HD kit.
The Exteme HD kit is designed around new driveshafts that feature 6 mm stub axles, large-diameter half shafts, and massive universal joints. It’s easy to see the difference between stock and Extreme.

The stock 4X4 driveshafts’ male and female halves engage via four square splines. The Extreme HD driveshafts’ engage via ten curvilinear splines. The greater number of splines means each individual spline carries less load, resulting in greater durability and longer shaft life.

Curvilinear splines and a precise fit assure smooth telescoping action under power. The large-diameter design resists twisting so your 4X4 puts full power into the tires in maximum-grip conditions no matter how hard you apply the throttle.

Larger driveshafts call for larger bearings. The Extreme HD kit’s rubber-sealed bearings are 20% larger than the stock parts for greater strength, longer life, and low-drag operation.

It’s easy to see the extra beef of the Extreme HD parts compared to the stock caster blocks, steering blocks, and hub carriers. By weight, the Extreme HD caster and steering blocks are molded with 50% more composite than stock. The rear carriers use 200% more material!

Here are the left front and rear assemblies of a stock 4X4 compared to the Extreme HD versions. The high-strength design and sheer size of the large-diameter driveshafts and suspension parts result in incredible durability.

Here’s a split-screen view comparing the Extreme HD shock towers with the stock parts. You can see how the camber link mounting points have been raised for driveshaft clearance.
Take Your 4X4 to the Extreme!
With just a half-hour or so at the bench, your 4X4 can go from Traxxas Tough to EXTREME Traxxas Tough. You can get the Extreme Heavy Duty Upgrade Kit in good ol’ black, or choose one of four custom colors and upgrade your truck’s style along with its durability. It’s your truck, do it your way! If you want to go even further, there are plenty more ways to customize and upgrade your Traxxas 4X4 (Note: Extreme HD components are not compatible with aluminum caster blocks, steering blocks, or axle carriers). Just follow these links to see all you can do with genuine Traxxas options and accessories for Hoss 4X4, Slash 4X4, and Rustler 4X4.
With just a half-hour or so at the bench, your 4X4 can go from Traxxas Tough to EXTREME Traxxas Tough. You can get the Extreme Heavy Duty Upgrade Kit in good ol’ black, or choose one of four custom colors and upgrade your truck’s style along with its durability. It’s your truck, do it your way! If you want to go even further, there are plenty more ways to customize and upgrade your Traxxas 4X4 (Note: Extreme HD components are not compatible with aluminum caster blocks, steering blocks, or axle carriers). Just follow these links to see all you can do with genuine Traxxas options and accessories for Hoss 4X4, Slash 4X4, and Rustler 4X4.
That completes our in-depth look at the Extreme Heavy-Duty Upgrade Kit. Check back next time for a full installation how-to guide.