WHY STOCK AXLES FAIL ON 40" TIRES
Running 40” tires changes the loads your entire drivetrain sees. What works on smaller tires often won’t hold up long-term.
Common failure points include:
- Axle shafts twisting or breaking under higher torque loads
- Ball joints wearing out quickly under increased weight
- Axle housings flexing or bending, especially during hard use
- Steering components struggling to handle larger tires
These issues don’t always show up immediately—but once you start pushing your vehicle on 40s, they become unavoidable.
WHAT AXLES ARE BEST FOR 40"+ TIRES?
If you're upgrading to 40”+ tires, axle selection becomes critical.
Most factory axles—and even many aftermarket Dana 60 builds—use 35 spline shafts, which can become a limitation under heavy use. Larger tires, more traction, and higher horsepower all increase stress on the system.
When evaluating axles for 40s, key factors include:
- Spline count (40 spline provides significantly more strength)
- Axle tube size and wall thickness
- Knuckle and steering design
- Long-term serviceability
This is why more serious builds are moving toward true 40 spline axle platforms designed specifically for larger tires and aggressive use.
WHY PEOPLE SWITCH TO FUSION
- Tired of replacing worn-out ball joints
- Done upgrading the same weak components
- Want true 40 spline strength front and rear
- Need an axle that can actually handle hard wheeling
- Industries best warranty
This isn’t an upgrade. It’s the last axle setup you’ll need.
BOLT-IN READY FOR:
- 2020-Present Jeep Gladiator JT
- 2018-Present Jeep Wrangler JL
- 2007-2018 Jeep Wrangler JK
- Jeep LJ, TJ, XJ, YJ, CJ
- Isuzu NPR
Shop Fusion 40 Spline Kingpin XL Axle Sets Now
TIRE SIZE GUIDE:
- Kingpin XL 60/60: Up to 40" Tires
- Kingpin XL 60/14: 42"+ Tires
- Kingpin XL 60/80: 42"+ Tires
- Kingpin XL 14/14: 42"+ Tires
KINGPIN VS. BALL JOINT: WHAT'S BETTER:
One of the biggest decisions in an axle upgrade is choosing between ball joint and kingpin front ends.
Ball joint systems are common because they are:
- Compact
- Cheap and easy to manufacture
- Very little labor to install in manufacturing
- Widely available
However, under the added stress of 40” tires, they tend to:
- Wear out quicky
- Require more frequent maintenance
- Become a long-term failure point
Kingpin systems, on the other hand, are designed for heavier-duty applications:
- Stronger under load
- Adjustable
- Proven in commercial and extreme-use environments
- Almost never require rebuilding or replacement parts
For builds running 40s and beyond, kingpin setups provide a more durable and serviceable long-term solution. Avoid the high cost of replacing ball joints.
GEN 2 HIGH CLEARANCE CASTINGS:
-
Every casting is designed for maximum ground clearance without sacrificing strength. The Gen 2 14 Bolt has nearly the same ground clearance as our high-clearance 60 castings, making it the optimal strength-to-ground-clearance ratio. Every housing includes an HD nodular iron differential cover with recessed bolts for rock protection.
INDUSTRY LARGEST 4" DIAMTER AXLE TUBES:
-
All Kingpin XL Axlescome standard with massive 4" DOM axle tubes — notably larger than the 3.5" (and 3.75") tubes found on most competitor axles (including many Dynatrac, Currie, and Ultimate Dana 60 builds). High and low pinion 60 versions can also accept 3.5" tubes when needed. The extra diameter translates to less flex and greater rigidity under load.
MASSIVE STEERING KNUCKLES:
-
Oversized knuckles allow greater steering angle while supporting larger shafts and spindles — delivering nearly50% more load capacity than standard designs.
TRUE 40 SPLINE STRENGTH:
Most axles in this category stop short.
We didn’t.
- True 40 spline shafts front and rear
- Lifetime Warranty
- Heat treated 4340 chromoly
- Massive increase in torsional strength
- Built to handle aggressive driving on large tires
Translation: Run your rig the way it was meant to be driven — without worrying about snapping shafts.
-
We use the largest wheel bearings in the industry, rated for over12,500 lbs GAWR — nearly 2x a standard Dana 60. Expect significantly longer life and total confidence on the trail.
HUGE FORGED CHROMOLY SPINDLES:
-
Forged and heat-treated chromoly spindles deliver4x the yield strength of an OE 14 Bolt full-float rear spindle.
FORGED HUBS + PLUG & PLAY ABS:
-
Tone rings are machined directly into the hubs, with sensor mounts for seamless ABS integration on Jeep JK, JL, JT, Isuzu NPR, and more. No reprogramming required.
BUILT FOR LONG-TERM SERVICEABILITY
This axle system was designed with long-term ownership in mind.
- Serviceable components
- Proven, reliable parts where it matters
- Built to minimize wear and replacement over time
The goal is simple: spend more time driving, less time maintaining.
DESIGNED, TESTED, PROVEN
- Extensive engineering and real-world testing
- Refined to eliminate weak points
- Built based on real customer needs and failures in the field
BUILT TO HANDLE REAL USE
This axle wasn’t designed for specs on paper.
It was built for:
- 40”+ tires
- Hard trail use
- High horsepower rigs
- Drivers who actually push their vehicles
When you’re on the throttle, this is the setup you trust.
Shop Fusion 40 Spline Kingpin XL Axle Sets Now
Have questions about fitment for your specific build? Our team is here to help you get it right the first time.