Dynatracs Full-Float Pro Rock 60 - 4-Wheel & Off-Road Magazine

Ali Mansour Brand Manager, 4WD & Sport Utility

Jeep obesity is a common problem. Whether it's a front bumper and winch combo, long arm suspension, or heavy-duty body armor, it all adds weight. While we enjoy aftermarket goodies as much as the next guy, have you ever thought about how much weight those parts are adding to your ride?

dynatracs Full Float Pro Rock 60 welding Photo 33384294

With a 4,300-pound curb weight it doesn't take much for the '07-to-current Jeep Wrangler Unlimited to put on some serious pounds when you add in gear, guys, and aftermarket parts. As a matter of fact, we've personally witnessed a few JKs weigh in at over 7,000 pounds! That's practically as much as a 3/4-ton truck. Never mind the power-to-weight ratio imbalance, but think about the increased load on the factory Dana 44 rear axle!

So what's a Jeeper to do? Since nobody likes going on a diet, the next best thing is to find a way to support the weight. What better way to support something heavy than to make it float? OK, not in the ocean, but on the street with the help of a full-float rear axle.

Found under most 3/4- and 1-ton trucks, a full-float rear axle is a severe-duty axle designed to support a lot of weight.

dynatracs Full Float Pro Rock 60 spindle Photo 33384531 The most basic and necessary piece of the full-float axle is the spindle. Composed of high-quality machined steel, the spindle is what supports the hub and secures it to the axle.

This is accomplished by fitting dual bearing hub assemblies over fixed-end spindles that are attached to the outer potion of the axletubes. Unlike a semifloat axle (Jeep's most common rear axle type), which uses a single axleshaft and bearing per side to support and propel the Jeep, a full-float axle doubles and enlarges the bearing support within the hub and separates the axle duties. This means the axleshafts are only responsible for propelling the vehicle, while the massive hubs handle the weight load.

Though the full-float axle is nothing new, the technology in the modern Jeep Wrangler JK platform has made it nearly impossible to simply pull a full-float axle from a junkyard and toss it into the rear of the sensor packed JK. Luckily, the legendary axle builders at Dynatrac have been busy crafting a full-float Pro Rock 60 for the '07-to-current Wrangler and have engineered the bolt-in axle to accept the factory sensors. To take a closer look at Dynatrac's new full-float assembly, we went to its headquarters in Huntington Beach, California. For this article we'll focus mostly on the full-float aspect of the axle, but you can find out more on the Pro Rock 60 specs and information at www.dynatrac.com.

PhotosView Slideshow Although the axletubes and housing are upgraded for increased strength and durability, the axle's hub is the epicenter for the vehicle's support. For the ultimate in load support, Dynatrac uses a proprietary hub design that provides increased strength and bearing spacing.
The Jeep Wrangler JK is packed with sensors from front to rear. To keep the onboard computer happy, Dynatrac's hub has tone rings machined in, which allow the factory sensors to work and read correctly.
Full-float hub assembly from left to right: exterior spindle nut, retaining ring, inner spindle nut, outer bearing, hub, inner bearing, seal.
PhotosView Slideshow Dynatrac's full-float axleshaft attaches to the hub flange and is secured by eight bolts. Since the hub is responsible for the weight of the rig, the axleshaft simply works to propel it. This version of full-float Pro Rock 60 received 35-spline shafts, but higher spline counts and custom axle lengths are available
The differential is a crucial part of the axle's strength. The Pro Rock 60 uses a high-pinion Dana 60 gearset, which is a substantial upgrade over the JK's Dana 44. While the hubs may do the heavy lifting, the ring-and-pinion takes the brunt of the force needed to propel the Jeep.
The complete assembly is just that: a complete factory replacement axle assembly. While bigger can be better, the full-float's massive hubs and big brake kit will require a larger wheel bolt pattern (5-on-51/2 or eight-lug) and you'll need a 17-inch wheel.