Knowledge is priceless. That's true generally, and it's especially true when you want to upgrade your 4x4's axles. Because of the investment and the work involved in this type of upgrade, it's important to select the right axle the first time, instead of enduring expensive and time-consuming trial and error. Clearly, there are criteria that should be factored into the selection process of an axle, including the weight and type of vehicle in which it's to be installed, the weight of the axle itself, the type of suspension being used, the location of the transfer case, what size tire will be fitted and what type of work the vehicle is being designed to do.
There are axles that you should consider because of their excellence, and some you should avoid because of weak design. To find out which is which, we asked a group of professional axle builders for their favorites. The following list, compiled from the answers those experts gave us, contains everything you need to know about 10 axles that the experts routinely build and install.
Now, before you dispute the findings in this guide--things like maximum recommended tire size, for instance--keep in mind that recommendations like these are meant only as a guide to reflect the performance and durability of said tire mounted to a bone-stock axle. We know that some of you will argue that you've had 44-inch tires on stock Dana 44 or GM 10-bolt axles under your fullsize truck for years without breakage--but bear in mind that we've factored in the axle's ability to endure slightly above-average abuse in its stock form while fitted with the listed maximum tire size. Conversely, those who wish to fit aggressive, large tires driven by high-horsepower engines and plan to use their vehicles as rockcrawlers or mud boggers may require a much stouter axle because of the inherent stresses caused by this type of terrain.
We've also included some facts, figures and building tricks for stock axles, and in order to make your hunt at the junkyard a little easier, we've asked the pros which vehicles sport the most desirable axles. After all, many of these axles have been manufactured for years and many have a significant number of variations depending on their original application. Some have gotten better with age, and some have not. For those of you who don't want to wander junkyards, we've also included a brief list of aftermarket companies that offer complete, ready-to-bolt-in axles (or third-members, in the case of the Ford 9-inch).