14-Bolt Basics - Inside The Ultimate Junkyard AxlePosted in How To: Transmission Drivetrain on May 1, 2013
When it comes to strength, value, and vast availability, the full-float 14-bolt rear axle from General Motors is about as good as it gets. Fitted with an impressive 10½-inch ring gear, three pinion bearings, and backed by a strong array of aftermarket support, the GM 14-bolt can easily handle up-to 44-inch tires in most applications. In case you're not familiar with the 14-bolt, the axle gets its name from the 14 bolts that secure the differential cover. First appearing in 1973, the 14-bolt is one of the most used rear axles in the General Motors stable.
Found under ¾- and 1-ton GM trucks, vans and SUVs, the 14-bolt received a max torque rating of 6,242 pounds. Up until 1994, GM manufactured the 14-bolt in-house. Post 1994, the 14-bolt was built by American Axle & Manufacturing. While the 14-bolt can still be found under many late-model GM 2500HD gas trucks and Suburbans, most '01-and-newer ¾- and 1-ton diesel trucks use the AAM 1150 rear axle. The AAM 1150 uses an 11½-inch ring gear, but retains the same axleshaft diameter as the 14-bolt.
Although there are a few versions, the full-float, 8-lug 14-bolts are the most desirable for those looking to build an off-road rig or upgrade their pickups light-duty rear axle. The 3¼-inch axletubes provide plenty of room for custom brackets and some of the pickup versions can be easily swapped into other makes with minimal fabrication. Maybe the best part about the 14-bolt is that they are plentiful in junkyards and can typically be picked up for less than $200 in operable condition. Aside from a few brake variations and a 18-inch diameter increase in the outside pinion bearing in the late '80s, the 14-bolt went relatively unchanged throughout its long run.
In this article we've taken hold of a late and early model 14-bolt axle to show you the ins and outs. We've even dug-in (literally) to our late model 14-bolt housing to install a shave kit from Ballistic Fabrication. What makes the Ballistic Fabrication Shave Kit a key upgrade for the 14-bolt is that it slices 2 inches off of the bottom of the massive 14-bolt housing. This is no small feat, but a tremendous upgrade for those looking to get the most out of their junkyard jewel. Ultimately, the 14-bolt is one of the most DIY-friendly axles you will find and can be made as high-end or basic as you choose.
Gaining 2 inches of differential clearance is nearly the equivalent of moving from a 31- to a 35-inch-tall tire. While we think the Ballistic Shave Kit is an excellent option for those wheelers looking to get the most off-road potential from their 14-bolt, it definitely isn't for everybody. For a ¾- or 1-ton truck that still hauls heavy loads and/or pulls trailers, the differential reduction may have more cooling and strength related cons than pros. The sheer amount of work involved and equipment required for the conversion are also serious items to consider.