The full floating rear axle has been around for decades. Primarily designed for heavy duty truck use, it was found to be a great solution for circle track racing and has been a race-spec axle housing used in all levels of circle track racing ever since. Today you’ll find high horsepower street cars that see extreme cornering g-forces (auto crossing, road racing, etc.) using full floater rear end setups as well. So why the change to a full floating axle from the more conventional semi-floating axle found under just about every rear drive production car made in the last century? It’s easy really when you compare the differences between full floating vs semi floating axle assemblies.
In a semi-floating axle, such as the popular GM 10 and 12 bolt rears, or Ford’s 7.5- and 8.8-inch rear ends, the axle assembly is retained by a C-clip at the differential end and rides on a single bearing seated in the end of the axle tube. The full weight of the vehicle rides on this single small bearing while the differential end of the axle shaft floats in the differential or spool, hence the “semi” floating term. This design puts a lot of stress on the axle bearings and seals and it is not uncommon to bend axle flanges in hard cornering or chew up a bearing (which ruins the axle). Additionally, if the C-clip should fail from side loading, or the axle break from excessive torque, the broken axle with wheel and tire assembly can exit the axle housing causing extensive damage and loss of control of the vehicle. While a bolt-in axle like the popular Ford 9-inch is an improvement, axle flange stress can still lead to bending or breaking right at the bearing in hard cornering.
Meanwhile, the full floating axle uses a hub that rides on a pair of large bearings on the end of the axle tube itself (similar to your front disc brake rotor and spindle). This allows the full weight of the vehicle, as well as all acceleration, braking, and cornering forces to move through the axle housing itself. Due to the dual bearing hub on the end of the axle housing the axle itself “floats between the differential or spool and a splined drive plate that mounts between the hub and the wheel (engaged via the wheel studs), thus the “full floater rear end.” If an axle should break in a full floating rear axle there is zero chance of losing a wheel and tire assembly. Furthermore, due to the fixed hub location disc brake pad knock back (a common issue on semi-floating axles where hard cornering pushes the caliper pistons into the caliper) is eliminated. This provides constant and firm brake pedal application no matter the cornering forces. Hit our Toolbox article on for more details.
Standard production car rear axles are assembled with thin wall press in axle tubes that often use nothing more than a couple of plug welds to secure. This allows the axle tubes to flex at the union with the main housing, causing axle stress, rear alignment changes, and fluid leaks. Sure, these areas can be welded, but you’re still left with those C-clips and the unsure feeling of what will happen if you ever break an axle. Our full floating rear end housing is a precision made fixture welded piece using all new thick wall steel, including the center section, which has a fully welded machined mounting surface for the third member, virtually eliminating any potential leaks at the housing to third member union. No ancient used center with just new axle tubes welded in here. The larger center section allows additional oil capacity for increased cooling (we recommend filling with 4 quarts of ). Oversized fill and drain plugs allow quick fluid changes or draining for differential/gear swaps.
Speaking of gear swaps, we know that you have at least a few 9-inch for various track conditions or track layouts/lengths and utilizing a full floater axle housing makes these gear changes effortless. Simply unbolt the drive plate cap, screw a 3/8-24 bolt into the end of the axle (or use our nifty ) and pull the axles out to clear the differential or spool and then swap to your needed gear ratio. No longer do you have to pull wheels, brakes, and more to slide out a traditional axle assembly to clear the differential or spool for pulling your third member for a gear swap. The included 31 spline axles will handle just about any power you can push downstream to the axle and are suitable for circle track, road course, and street use, though we do not recommend for extreme high horsepower drag racing use, which generally relies on 35 or 40 spline axles.
Utilizing industry standard 3-inch axle tubes allows just about any suspension system to be used with our full floating axle assembly. From 3 and 4-link setups, to triangulated rear suspensions, even leaf springs and circle track birdcage systems, whatever suspension you plan to run will work with these axle tubes. The same can be said for your choice of brakes. Using standard weld on or clamp on for your choice of caliper to compliment the included .810-inch thick 11.75-inch vented rotors included. These axle tubes feature a standard 2.625-inch ID, allowing optional to be installed for better oil control if desired. Axle lengths are measured from hub to hub and are available in 56-, 58-, 60-, and 62-inch widths with a centered pinion location.
The included Grand National style hubs include tapered roller bearings, tabbed lock washer with retaining nut to maintain bearing preload, and inner axle seal with spiral lock ring retainer. These hubs are available in either 5x5 or 5x4.75 bolt circle patterns. Both bolt circle patterns use 5/8-11 coarse thread wheel studs and include 1-inch double sided lug nuts. Due to the larger wheel stud and the 45-degree taper of the included circle track-style lug nuts most street-style wheels will not work with these hubs. If your wheels of choice use standard 1/2-20 wheel studs and 60-degree taper lug nuts, you can replace the wheel studs included in this kit with our special Grand National on the 5x4.75 bolt circle pattern hub only (5x5 hub is press fit studs and not compatible with these optional screw in studs). You can learn more about 45 vs 60 degree taper lug nut applications in our in The Toolbox.
Kit Includes:
Summary: All brand new housing great for welding suspension brackets to, all other parts look good too.
Yes, I recommend this product.
Summary: Great value for the price and very well built. I will be upgrading the axles to shouldered ones for oil seals as this is going into an autocross/ track day 1966 Malibu that will see a lot of lateral force and will need to keep the gear lube in the center section. The new housing looks to be much better braced than getting one with a reclaimed center. It also comes with the third member studs installed, which aren't listed on the parts breakdown or visible in the pics. Does have a package of bolts marked "hub back" that I can't find where they go, but that's nothing. I would recommend getting solid bearing spacers for the hubs to make the included import bearings have less heat and friction from use.
Cons: Not really
Pros: Very well made. Customer service was fantastic.
Yes, I recommend this product.
Summary: Very nice looking welds on the housing. Good deal for the price. Only thing is in description it says all seals included. Kit does not come with inner axle seals.
Yes, I recommend this product.