10-Bolt Builder’s GuidePosted in How To: Transmission Drivetrain on November 6, 2013 0) (
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
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.