Have you fit your rig with bigger tires? Do you use your rig off-highway? Have you increased your rig's horsepower or torque?
If you answered yes to any of these questions (and we're sure you did), it would be prudent to consider upgrading your rig's axleshafts. You see, the axleshafts in your rig's axles were designed to function inside of certain parameters. When you fit bigger, grippier meats and attack a rough trail or start shoving more power to the axles, you will most likely exceed those parameters. So what will happen? Well, an axleshaft can snap; the splines can twist; or if we're talking front axles, the axle joints can be the weak link and self-destruct.
So what's the big deal? You can just drive slow and limp back to town, right? Uh, no, not always. Depending on the axle, the breakage may cause collateral damage (damage to other critical components) and/or the breakage can cause the vehicle to be immovable. Naturally, this is a major inconvenience and it could be life-threatening if you're 20 miles from help in the middle of nowhere.
Here you can see the Randy's Ring & Pinion front and rear axles, Super Joints, bearing kits, and other components that we installed. We also installed a pair of 35-spline lockout hubs to go with the new 35-spline outers.
The solution is to install a pair of upgraded axleshafts and U-joints before the stockers puke. Sure, this takes planning and money, but in the long run you'll save yourself the hassle and embarrassment (at the very least) of an incapacitated rig.
We want to give you the lowdown on what it takes to upgrade the axleshafts on two popular axles-the Dana 60 front and the GM 14-bolt rear. In this case, both axles are under a 454ci-powered '98 GMC Suburban 3/4-ton that rolls on 35-inch tires. The rig is a workhorse that is routinely used both on- and off-highway. We contacted two companies we trust: Randy's Ring & Pinion for the parts, and Custom Differentials for the installation. From Randy's we procured its Yukon alloy axleshafts for the 14-bolt, a Yukon Dana 60 4340 35-spline axle kit, a pair of Yukon 4340 chromoly Super Joints, and a pair of Dana 60 wheel-bearing kits. Ordering from Randy's is as easy as picking up the phone, thanks to the toll-free number and knowledgeable sales team. The team of technicians at Custom Differentials in Bloomsdale, Missouri, installed all of the components while we took photos. The axle gurus at Custom Diff can handle any axle build from mild to off-the-hook wild. This install was another day at the office for them.
Follow along as we show you how it all goes together and how the stock components pale in comparison to Yukon's beefy aftermarket components.
1. We began our upgrade on the Suburban's front axle. The axle we're upgrading was originally under an '86 Ford 1-ton truck. To get the front axles out of the axlehousing, Custom Differentials technician Patrick Naeger drained the diff lube and then removed the brake calipers, lockouts, wheel bearings, hub/rotor assemblies, and spindles. With all of these items out of the way, the axleshafts can be slipped out. | 
2. Since the Yukon axleshafts are far stronger than stock, it's a no-brainer that strong U-joints should also be installed. Randy's offers two strong joints that work well in an application such as this. On the left is a beefy forged Spicer alloy joint that is much stronger than a stock U-joint. It's a good upgrade, and it's quite adequate for most folks when paired with Yukon alloy axleshafts. On the right is the awesome Yukon Super Joint, which is what we opted to use. They're priced quite a bit higher than the alloy joint, but they're also substantially stronger. In addition to their 4340 chromoly needle-bearingless construction, they feature O-ringed seals to keep out impurities and full circle retainers on the caps to ensure a tight fit. Their rock-solid construction makes them some of the beefiest U-joints you can buy. | 
3. Quarters illustrate the difference between the shaft diameter of the stock stub shaft (left) and the increased diameter of the new Randy's stub shaft (right). Not only is the shaft diameter larger, but also the spline count is increased from 30 to 35 when compared to stock. |
4. Because of the increase in spline count and the larger diameter of the new stub shafts, we also had to install a pair of 35-spline lockout hubs. On the left is one of the new units; on the right is the stock lockout. Notice the larger center hole in the new lockout that will accept the larger-diameter stub shaft. | 
5. The technicians at Custom Differentials always inspect the wheel bearings, races, and seals while the spindle is off the vehicle. Ours were showing signs of wear, so the old ones were removed and replaced with the Randy's new wheel-bearing kits. They also always replace the inner axle seals. | 
6. Here you can see a portion of the new inner axleshafts. The top unit is the Yukon alloy shaft and the bottom is the stock shaft. The differences between the two are significant. Not only is the 4340 material far stronger than that used on the stock shaft, the Yukon alloy shaft is the same diameter from yoke-to-spline (the stock shaft necks down near the yoke); the yoke is machined to take stronger full-circle U-joint clips; and there's much more material in the yoke area overall. Most Dana 60 axles are 35-spline at the differential, so there's no increase in differential spline count. |