With AxleTech International Motorsports' new bolt-on portal boxes, you get a geared hub that goes on the end of your axle and raises the centerline of the axle tube 5 inches above the centerline of your wheel. Portals have been around for years under all types of military vehicles and tractors, but never has there been a bolt-on kit for the tried and true Dana axles.
Inside the geared hub of most portal axles are only two gears, which makes them difficult to attach to a standard axle since they require flipping the differential due to the direction reversal of the two-geared hub. The AxleTech portals have four gears: a drive gear, two idler gears, and a massive driven gear that keeps the drive direction constant, meaning no axle (differential or third member) flipping is needed, and it lowers your gearing by 50 percent. Since these geared hubs are at the end of your axles they give your ride a lot of ground clearance without a suspension or body lift.
So why hasn't anyone done this before? We're not sure, but these guys are definitely qualified to make it happen. AxleTech is a descendent of such well-known axle component companies as Timken, Arvin Meritor, and Rockwell International. The company that made the Rockwell 2 1/2-ton axle is a forefather of AxleTech. The company now concentrates on planetary and portal axles for heavy equipment and military vehicles and felt that its expertise would be perfectly suited for making parts for the wild wheelers in the off-road market.
These portals are the first prototypes installed on a vehicle, and we're proud to say our Fun Buggy was chosen as the guinea pig. The best part is that we bolted them onto the front and rear kingpin Dynatrac Pro Rock Dana 60s with no problems! We've only just begun testing them on the trail, but AxleTech has been putting them through high-speed and high-torque destructive testing and has yet to break the boxes (watch the video on AxleTech's website).
The portals are currently available for kingpin Dana 60s and Corporate 14-bolt axles, but will soon be made for various front and rear axles (rear axle applications may require welding), and a smaller lighter version is coming eventually for half-ton and smaller axles as well as IFS.
1. The AxleTech portal boxes...
1. The AxleTech portal boxes have four gears inside, each 60 mm wide (2.36 inches) and made of heat-treated 8620 steel. The upper drive gear has an internal 35-spline that receives the new stub shaft. The bottom drive gear has a 41-spline, 53mm-diameter (2.09-inch) output to the drive flange where the wheel mounts. The gear multiplies the axle ring-and-pinion ratio by 1.5, such that 5.38 now equals 8.07, thus reducing stress on axleshafts, U-joints, and everything upstream.
2. The AxleTech design uses...
2. The AxleTech design uses a portal box and a separate knuckle or adapter at each corner. The same box can be adapted to a variety of different axles. The stock Chevy Dana 60 kingpin knuckle is on the left, and the AxleTech International Motorsports (AIM) knuckle that we replaced it with is on the right. Everything from the inner "C" outward is replaced with AxleTech parts; all you re-use is the inner shaft and the U-joints, upper and lower kingpin components, and the top plates and/or steering arms.
3. The AIM stub shaft is identical...
3. The AIM stub shaft is identical to a Dana 60/70 stub shaft, just shorter. It is made of forged chromoly with rolled splines and accepts Dana 60 U-joints or our bombproof CTM ones. The stub shaft is held in place with a small retaining bolt on in the top gear of the portal.
4. The AIM knuckle use six...
4. The AIM knuckle use six M12 high-strength bolts that are 12 mm in diameter (0.47 inch), are Class 10.9, and come with two alignment dowels to attach and locate the portals. The upper kingpin retains the stock bushing and spring design, but we are considering other options if the added leverage of the portal box causes problems. We reused our OTT Industries five-bolt high steer arms, but the knuckles can accommodate up to a six-bolt steering arm.
5. The nodular iron portal...
5. The nodular iron portal box isn't the lightest accessory, weighing a total of 158 pounds per corner, but when replacing all your factory kingpin axle parts you only gain 60 pounds per wheel end. The gear box is O-ring-sealed and bolted and pinned for protection against contamination during deep muddy wheeling.
6. The brakes are nearly 13-inch...
6. The brakes are nearly 13-inch rotors, with one or two Wilwood four-piston calipers per wheel end. (Production version boxes will have the caliper up along the side of the box, not on the bottom.) The portal box uses standard API GL-5 80W90 gear oil, and we outfitted our brakes with extra-long Russell DOT brake lines.
7. The portals add roughly 5 inches of ground clearance and 5 inches of width per side. The width is easily dealt with by running high backspacing wheels (see sidebar), and the ground clearance is great for mud, snow, and rock wheeling. In fact, we ended up with 18 inches of differential clearance with 30 psi in 40-inch tires.
Portal Wheels
With the additional width of the portals, it is important to find wheels to deal withthe added leverage and scrub radius. To get back to a reasonable overall width, we swapped in some 17x10 steel wheels with 8 3/4 inches of backspacing made for AxleTech by Stazworks Extreme Offroad. The Wheels are a two-piece design with an internal beadlock very similar to HMMWV military wheels.
The portals are made to clear a HMMWV wheel. Stazworks can also supply them if need be, but they are only available in 16.5-inch, whereas we like the greater tire options of the 17-inch. You will need to supply the valve stems and take your time assembling the wheels and the internal O-ring seals. We have had great success so far. They haven't leaked, and they hold the tires firm during severe side-hill wheeling. The extreme backspacing protects the brake calipers and reduces stress on the kingpin components.