Kevin McNulty
Former Editor, Mud Life
Photographers:
Chris Hamilton
No doubt 2½- and 5-ton axles are the meat-and-potatoe axles of built mud rigs. They are cheap and tough compared to other common axles that are available. The only downside to Rockwells is that they are huge, bulky, and heavy. That statement will have to be taken with a grain of salt because we can’t really say the large Rockwell/military-style axles are a hindrance to performance because they are commonly installed on competition-winning mega trucks. Whatever the difference is between a Rockwell and other common axles like 1-tons, they both can be fitted with gearing and lockers. However, the smaller 1-ton axles like the Dana 60 and 14-bolt axles are more common, have performance attributes related to their smaller size, and have more aftermarket performance parts available.
Dana 60 and 14-bolt axles can be found on many common production trucks spanning decades. Any good wrecking yard should have some lying around and ready for the taking; just look for the larger trucks. The benefit of these 1-ton axles is the bevy of performance parts like gears and lockers. They also allow more uptravel because there is no top hat/pinion sitting on top of the axle.
PhotosView SlideshowWe needed to upgrade the axles on our buggy—the stock 1-ton axles just weren’t cutting it. We were looking for lockers for additional traction, gears to even out the buggy’s final drive ratio, and a conversion kit to get rid of the Dana 60’s vacuum-actuated axleshaft disconnect. We checked out Yukon Gear & Axle’s website and ordered up 4.88 gears, chromoly shafts for the front and rear, and a Zip Locker and vacuum disconnect conversion for the front Dana 60. We pulled the axles from the buggy and took them over to our buddies at Bigg Boy Auto for a little help with the install. These guys are the experts for gears and repairs in our area. Installing gears and lockers can be complicated but not so much that the average mechanically inclined home mechanic can’t do the job himself. Follow along as we walk you through our gear and locker install.
We like doing business with Yukon Gear & Axle, a company that knows axle tech and is easy to work with. The axle components we needed were at our doorstep in just a couple of days. For anyone contemplating rebuilding axles, a wealth of tech information is on Yukon’s website. We also recommend the book Differentials by Randy Lyman and Doug Alan, available on the Randy’s Ring & Pinion website.
The Zip Locker from Yukon was one of the main goals of rebuilding the axles. The pneumatic locking differential is the perfect locker for a front axle, simply because it can be locked and unlocked at the flip of a switch, plus it gives our buggy real four-wheel-drive traction. If you are just learning about axles and wondering why it’s better to lock and unlock, it’s because a locked front axle has a smaller turning radius and for street-driven rigs it is tough on tires.
Nasty! So maybe we should have been checking, changing’ and keeping tabs on our differentials, but what the hell. We knew we were going to rebuild them. This is what happens to differentials when they’re driven in deep mud and water. The key to longevity is maintenance, good seals, and long breather tubes, none of which we cared about until now.
The front axleshaft conversion kit for our Dodge Dana 60 gets rid of the problematic vacuum disconnect and weak two-piece shaft. The factory stub shafts/outers are reused and need to be installed on both of the new chromoly axleshafts; chromoly will be available sometime soon!
The outers are attached to the inner shafts by U-joints, and changing them out isn’t too difficult for mechanically inclined folks. We should have replaced the U-joints long ago—this is what water and mud contamination does to unsealed needle bearings.
After removing the fluid and giving the axle a good clean, we were ready to install the new ring gear and locker. This is a good time to check the case for cracks and wear that would compromise the new components going inside.
Anytime bearings are installed on pinions they should be properly measured with calipers. Calipers are cheap and can be used to measure a number of important components in and around a truck.
Proper measurement will stop bearings from destroying the surfaces they are supposed to protect.
Once the bearing are in place the ring gear can be bolted to the locking differential. The proper torque specs should be used, and red Loctite should be dabbed on the bolts so they don’t back out and destroy the whole assembly.
Since the Yukon Zip Locker is pneumatic, a copper air line needs to be run through the differential. A hole must be precisely located and drilled through the differential housing.
The Zip Locker will run off any source of air, such as a small compressor, but it must be able to supply a constant 90 psi.
The new differential can be placed in the
housing once the carrier bearings are in place.
After the pinion depth and backlash are
determined and set (this may take a few tries)
the side-to-side movement needs to be set.
A dial indicator and master set of shims are
available from Yukon.
Last but not least, a pattern check
on the ring gear needs to be run.
The pattern or gear mark in the
paint shouldn’t be too shallow or
too deep and should be centered in
the tooth of the gear. If it’s wrong,
the setup and measuring needs
to be done all over again. There
is a science to setting gears and
how they work, which we will get
into in our next ring-and-pinion
installation article.
