Part 16: Dana 60 Front Axle Beef
(Editor's note: We know. We've done Dana 60 swaps before. But before you skip ahead to the next article, we're going to examine all the common failure points of the Jeep Dana 30 and 44 and physically contrast them to those of a ProRock 60 from Dynatrac. We hope to shed some light on the major differences in strength between what the factory put in all Jeeps and what we think will live when used on the trail.)
Some of you may remember back in the May '05 issue when we upgraded Teal's Super Dana 44 with CTM U-joints and a Warn premium hub conversion. At that time, we guessed where we had moved our new failure point--and shortly afterward, we lunched the front ring-and-pinion. A Dana 44 ring gear is no match for Superior Axle's chromoly shafts, CTM U-joints, 37-inch rubber, and Hemi power.
Now, our beloved teal trail rig is no trailer queen. However, we do flat-tow her quite often. As such, we require her axles be able to handle the long haul as well as tackling tough terrain. This means we couldn't just swap another Dana 44 under her and expect it to last. That's why we went back to Dynatrac in Huntington Beach, California, for another ProRock 60 axlehousing, this time for the front. (We installed a ProRock 60 under Teal's caboose back in the Aug. '05 issue.) Why did we decide on another ProRock axle? Read on.
The most common failure point of any axle is the bearings. This is where most of the friction occurs. Conventional wisdom says bigger bearings are always better, but to use bigger bearings, you need a bigger housing. This is where it all starts. A Dana 44 centersection weighs somewhere in the neighborhood of 33 pounds, whereas a high-pinion ProRock 60 centersection chimes in at about 88 pounds. A larger housing also means more oil volume, which equals better cooling, which translates into longer bearing life. A Dana 44 axle's capacity is 3 quarts of gear oil, a pittance compared to the Dana 60's 6-quart capacity. The ProRock housing takes these numbers a step further by offering two separate sumps, each with high-volume flow to each of the pinion support bearings. Even better are the ProRock 60 lightened centersections (left). These custom-machined units have more than 23 pounds of material shaved off of them to make the lightest steel Dana 60 money can buy. These are perfect for lightweight buggy buildups.
Next up for comparison are the actual bearings. This shot shows Dana 30, 44, and 60 carrier bearings. The larger Dana 60 carrier bearing is rated to support up to 5,200 pounds, whereas the 30 and 44 are rated at around 3,500 pounds. The actual difference in size is easy to see.
Probably the weakest link when it comes to 'wheeling, U-joints are designed to transfer torque through a specific range of motion, i.e., steering radius. However, for this article we are going to stick to the idea of a failure occurring when the wheels are pointed straight ahead. A Dana 30 or 44 U-joint (Spicer PN 5-760L) typically will start to fail at around 1,600 lb-ft of torque with a consistent torque load. The Dana 60 U-joint (Spicer PN 5-806X) will start to fail at around 3,300 lb-ft in the same situation. The newly patented CTMs, such as those that Dynatrac installed on our front axle, are made from 300M tool steel and rarely, if ever, fail. However, they do require more frequent greasing to last as long as a joint equipped with needle bearings. We feel the CTM U-joint is a worthwhile upgrade for any hub-equipped trail rig with larger-than-stock tires. However, it's important to know that installing them will probably void any aftermarket axle manufacturer's warranty.
Other axle parts we see fail quite often are stub axles. At left is Superior's high-strength alloy stub shafts. These are forged from 4340 chromoly alloy steel, said to be the strongest raw material axleshafts can be mass produced from. They also have rolled or hobbed splines. These two spline-building techniques are said to produce better splines than shaping, fly-cutting, or other methods used by the industry. Next to it is the Dynatrac ProRock 60 shaft. These shafts, hands-down, are better than the Dana 44 and 30 stubs shown to the right. However, they do not come with a corrosion-resistant black oxide coating like the Superior shafts. Like many of our readers, we've been known to drop the hammer to get a rig up over an obstacle, which is why we went with the Superior upgrade.
This photo demonstrates the difference between the Dana 30, 44, and 60 inner axles. Both Dynatrac and Superior Axle offer a larger-diameter 40-spline Dana 60 axleshaft. These are designed for competition use and require a special 40-spline Detroit or ARB Air Locker to function. We didn't see the need to run the 40-spline axles on Teal-J.
Ring-and-pinion gears fail all too often. Typically, it happens to rigs with larger tires and/or higher-powered engines. In most cases, a high torque load cracks the teeth of the ring gear first, which almost always causes complete failure of both the ring-and-pinion gears. Here you can see how much bigger the Dana 60's gears are over the 44's and 30's.
In the hub arena, there are two popular options: lockout hubs like the Warn Dana 44 and 60 (left) or drive flanges (right). There is some disagreement about which is best when it comes to failures. In general, we think that the bigger the hub, the better off you are. However, there are varying opinions about hub failures when it comes to performing a trail fix. The lockout hub is easy to repair on the trail with basic handtools, a good thing if you're out with a group. On the other side of the argument, a hub is considered a weak link that should be eliminated before leaving the pavement. The best way to do this is to install a pair of drive flanges. These provide a permanent, solid connection in place of a lockout hub. The problem with drive flanges is that they rarely fail, which means if you do break something on the trail (i.e., axle, U-joint, or gears), it's going to take much longer to fix and will probably be a lot more expensive to replace. Our opinion is this: Hubs are for trail use, drive flanges are for competition.