The GM 10-Bolt semi-floating rear axle has been in use for over 40 years. It’s been used in passenger cars, and light duty pickups and SUVs over the decades. In the off-road world, you’ll typically find them under full-size 1/2-ton and some 3/4-ton GM trucks, Blazers/Jimmys, Suburbans, Tahoes/Yukons, and Cadillac Escalades.
The rear axle is a C-clip design unit, meaning the axleshafts are retained using a metal C-clip in the middle of the differential. In the early days, the ring gear size was 8.5 inches, but the size increased to 8.625 inches mid-1999. The pinion is a 30-spline piece and the pinion nut is 1 1/4 inches. Axleshaft spline count can be either 28 or 30 splines.
The 10-Bolt has proven itself over the years to be a decent performer in mild to medium duty off-road applications. Obviously, the 30-spline axle option is the preferred choice for added strength. We’ve seen these axles survive reasonably well under fullsize trucks and Blazers with 35-inch tires. That’s assuming they’re not stressed hard in rocks or impact loaded on a regular basis.
Push these axles much harder, the tubes begin to flex, possibly resulting in differential wear and ultimately carrier failure. These axles are good to upgrade if they’re the existing axle and you refrain from pushing past the limits we mentioned. Those who need more beef than the 10-Bolt may want to search out a Corporate 14-bolt or Dana 60. Depending on your vehicle, either could be nearly a bolt-on affair. However, pinion yokes or U-joints may differ from the 10-Bolt and the heavier axles usually have 8-lug wheel lug patterns.
Given that this axle has been in production for so long and in so many applications, you have access to wide aftermarket support, including ring-and-pinion ratios up to 5.57:1. Your limited slip and locker choices are immense, and alloy replacement axle shafts are readily available. Items such as C-clip eliminator and disc brake kits are on the market as well. OR
Step By Step
The 8.5-inch or 8.625-inch (commonly called 8.6-inch) ring gear is held to the carrier with 10 bolts. Both differentials use the same ring-and-pinion sets, and most parts are interchangeable between the two differentials. However, the carrier bearings are distinctly different in size.
Aftermarket traction-aiding devices include ARB air lockers, Detroit, Powertrax Lock-Right, Spartan, Yukon Dura Grip, Yukon Grizzly, Eaton Posi, Eaton E-Locker, Truetrac, mini spools, and full spools.
The factory Gov-Lok used in some 10-Bolt axles is relatively weak and has limited life when used off-road. We’ve heard of more than a few that have grenaded. This one from a Chevy Blazer has a cracked differential case, which led to destruction of teeth on the side gears inside. In any case, upgrading any factory 10-Bolt carrier is advised.
Aftermarket chromoly shafts are readily available and not that expensive of an upgrade. Installing new alloy shafts in place of decades-old stock shafts should guarantee greater life from your axles when running bigger tires or lockers in your axles.
This factory 10-Bolt axle shaft was starting to wear due to age and loading. The bearing surfaces were pitting and the oil seal surface showed signs of long-term wear as well. It’s best to install fresh bearings with new shafts to avoid premature wear to the shaft surfaces.
The 10-Bolt axles came in 28- and 30-spline versions. Those with a 28-spline axle looking to do some upgrades can easily step up to the heavier 30-spline setup. Purchase replacement shafts that are 30-spline and a 30-spline differential at the same time. All other parts are compatible.
It’s possible to get rid of the C-clip axle retention by installing safety hubs or a C-clip eliminator kit. Strange Engineering offers a bolt-on hub kit with captive axleshaft bearings used to retain each axleshaft in the housing.
The 8.5-inch version axles were drum brake equipped. The later 8.6-inch axles came with disc brakes, with some overlap during 1999.
Disc brake conversion kits are available, such as this one from Right Stuff Detailing. A properly set up rear disc kit can offer superior braking over factory drum brakes. Plus, if you live in an area where you drive through mud and water a lot, the open design of a disc brake allows you to clean out sand and debris better than a drum brake unit.
In the dirt and rocks, sheetmetal differential covers are prone to impact and denting. This either pushes the cover into the ring gear, which starts to wear a hole in the cover, or the dent distorts the edge seal area and the cover starts to leak gear oil. Aftermarket replacement covers or guards can help prevent these issues. All 10-bolt version axles use the same cover.
Typically, a GM 10-Bolt came from the factory with a 1310-series U-joint yoke with metal retention straps like the stock one shown here. Yokes are readily available to upgrade to the much stronger 1350-series joint using more reliable U-bolts for retention.
Stronger Factory 6-Lug Option
If the 10-Bolt just isn’t going to be enough axle for you, but you want to retain that 6-lug wheel pattern, try scouting out a heavy-duty 6-lug axle like the semifloating 6-lug 14-Bolt axle. Unfortunately, these axles are not that plentiful, or you’d see a lot more 6-lug half-ton off-road trucks running around with them.
The 6-lug 14-Bolt is a nice axle for GM half-ton owners who want an almost drop-in HD replacement. There is only half an inch added to the pinion yoke length, making the existing driveshaft reusable with a conversion U-joint. The spring pads line up, and the widths of the truck 10-Bolt and the 6-lug 14-Bolt are within an inch of each other.
Not only do you get a 9.5-inch ring gear by switching to a 6-lug 14-Bolt axle, you get larger axleshafts and much larger drum brakes. The larger drum brakes do still fit within a 15-inch wheel, though.