Our donor Chevy Silverado...
Our donor Chevy Silverado was built in 1989, wore the 2500 badging, and featured six-lug wheels. GM offered this configuration to bridge the GVWR gap between the 1500 and the 2500 series. Today these light-duty 3/4-tons are easy to spot in wrecking yards-just count the lug nuts and cross-reference the model badging on the door.
The GM Corporate 14-bolt axle is one of the most favored rear-ends you can find used for under $500. Most wrecking yards have a pile of them in stock, and due to a substantial production run across all variations of HD pickup trucks and SUVs, chances are you can find the specific type you need with minimum effort. Enthusiasts love the full-floating eight-lug 14-bolt because it features a massive 10.5-inch ring gear, and a very strong pinion design that incorporates support bearings on each side of the pinion's teeth-awesome for minimizing pinion deflection under high torque applications.
However, most people are not aware of the less common six-lug, semi-floating version of the 14-bolt axle. GM called it the "9.5" 14-bolt (after its ring-gear diameter) and offered it exclusively in light-duty 3/4-ton pickups built between 1986 and '93. While not as strong as its eight-lug cousin, the semi-floating 14-bolt rearend does sport some noteworthy attributes. For instance, the all-important width measurement from wheel mounting surface to wheel mounting surface is 67 inches-perfect for most 1/2-ton pickups. Generally, you wouldn't even need to change mounting brackets to bolt this housing right into the rear of a 1/2-ton GM pickup because the leaf spring architecture is identical. We like the fact that the ring gear measures out at a healthy 9 1/2-inch diameter, and the 33-spline axleshafts have a 1.370-inch diameter-a sure improvement in strength over the typical 1/2-ton shafts. This less grown-up version of the 14-bolt may not have the extra pinion support bearing of its eight-lug cousin, but it's rated to handle 5,000 lb-ft of torque, so it's no lightweight either. Moreover, aftermarket suppliers such as Randy's Ring and Pinion offer all the upgrade goodies you need to make this rear end survive with up to 37-inch-tall rubber. As a result, owners of virtually any GM 1/2-ton pickup offered with six-lug wheels can benefit greatly from a semi-float 14-bolt axle upgrade.
Here is the kicker: Thanks to the semi-floating design, a factory-style wheel will bolt right up. This means you do not have to spend your hard-earned cash on eight-lug wheels to get vast improvements in overall axle strength. We think these axles are the cat's meow for trucks equipped from the factory with 10- or 12-bolt rear axles. Yes, you'll need to ensure proper gearing for your truck, but know that most semi-floating 14-bolt axles have the common 1/2-ton 3.73:1 gear ratio already installed, rather than the popular 4.10:1 ratio found in the full-floating version-so if you already have 3.73:1 gearing, you may save additional money. Otherwise, depending on U-bolt length and pinion yoke type, the job is a no-brainer.
For this story, we borrowed a friend's '89 Chevy Silverado 3/4-ton with the less-common semi-floating axle installed from the factory (this is the donor truck you would want to find at a wrecking yard). Follow along now as our friends from Right Gear and Axle of Salinas, California, help us fortify a semi-floater for 35s, light towing and occasional trail work.
With the vehicle secured properly...
With the vehicle secured properly on a lift, Right Gear's technician started the teardown process. While this was happening, we unpacked a shipment of goodies from Randy's Ring and Pinion. They sent us everything we needed to make our 9.5 14-bolt a true contender for 35-inch tires and light trail work. Shown are a set of 4.56:1 gears and a complete installation kit, as well as an Eaton ELocker for added traction when the trail gets tough.
Randy's Ring and Pinion also...
Randy's Ring and Pinion also supplied us with a pair of their 1541H alloy axleshafts for the 9.5 14-bolt rear axle. Theses shafts are said to be 30 percent stronger than stock while remaining low-cost for an exceptional value for those who want to run a larger tire with stock power levels.
Once the pumpkin was drained,...
Once the pumpkin was drained, we noticed a large amount of metal debris attached to the magnet inside the bottom of the center section. (We like magnetic drain plugs because they give us a clear picture of how much wear occurs inside a differential over time.) This truck had roughly 135,000 miles on the odometer. The vehicle's owner told us that the gear oil was changed twice during the truck's life, so this much-needed overhaul was, in fact, perfect timing for our donor truck.
With both axleshafts and the...
With both axleshafts and the factory open differential removed from the housing, the technician started the process of driving the pinion gear out of the housing. It took several hard blows from the hammer to free the worn pinion from the housing.
Next, the technician turned...
Next, the technician turned his attention to readying the differential for new parts. Here you can see how the remnants of the old gasket were removed using a pneumatic grinder. Once removed, the whole inside was bathed with solvent to remove unwanted oil and debris.
As the axle was being prepped...
As the axle was being prepped for the new parts, another technician installed the new ring gear on the new Eaton ELocker.
With the locker in place in...
With the locker in place in the differential housing, the technician figured out exactly where to drill the access hole for the two-wire electric harness included with the ELocker. A 1/4-inch hole was drilled moments later.
Setting up a good wear pattern...
Setting up a good wear pattern is critical for trouble-free axle operation. As you can see here, the teeth of the our ring gear were set up to engage near the middle of each tooth (see where marking paint is thinnest); this engagement pattern will help distribute the torque over the whole surface of the gear rather than concentrating it to just the outer edges of the teeth.
This photo shows how the ELocker...
This photo shows how the ELocker wiring arrangement looked after the grommet was installed in the 1/4-inch hole drilled by the technician. A little dab of silicon sealant can help keep water from entering through this grommet.
Once the new differential...
Once the new differential locker was installed, the technician installed the new axleshafts. The original diff cover was cleaned and re-painted black, and each of the 14 differential cover bolts were replaced for a fresh clean look. Notice the small metallic tag installed by the technician; we love seeing this because it typically shows that the installer took pride in his work.
With the axle completely buttoned...
With the axle completely buttoned up, we added two quarts of Max-Gear synthetic gear oil by Royal Purple. We picked this lubricant because it offers added protection to bearings and wear surfaces by coating them with a slippery film called Synslide. It's a term for the technology that Royal Purple developed by using a proprietary mixture of synthetic-base oil and high-tech additive compounds. We like this technology because it displaces water from metal surfaces and excels in protecting metal components in wet environments. It also fortifies the oil against the detrimental effects of heat, which causes oil to oxidize and wear out.