9 Inch Grand National Hub Floater Rear End Kit, 31 Spline Axles

• Machined full floating axle housing design with fully welded 3-inch axle tubes
• Axle tube diameter compatible with numerous suspension designs
• Fully machined 2.5-inch axle tube ends for fitting Grand National hubs
• Lightweight steel hubs use 2.5-inch ID tapered bearings for increased loads
• Axle housing features centered pinion design for maximum driveshaft clearance
• Available in 56, 58, 60, and 62 inch wheel flange to wheel flange measurements 
• Floating hubs are offered in 5x5 and 5x4.75 wheel bolt patterns with 5/8-11 studs
• Includes 31 spline solid axles that fit popular differentials and spools
• Housing includes oversized fill and drain plugs for easy fluid changes
• NPT threaded axle vent located on main housing
• 24-spline drive plates with aluminum axle caps allow easy axle removal
• 11.75-inch disc brake rotors, bearings, seals, and hardware included
• Only needs disc brake calipers/mounting brackets, and center section to complete

Upgrade To a Full Floater Rear End for Increased Strength and Safety

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 full floater rear axles for more details.

Strength and Precision That Can Handle the Track or The Street

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 gear oil). 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 differential housings 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 axle pulling tool) 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.

3-Inch Axle Tubes Compatible with Popular Suspension System Options

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 disc brake caliper mounts 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 inner axle housing seals 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 1/2-20 wheel studs kit 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 lug nut guide in The Toolbox.

Kit Includes:

• 9-inch Grand National full floater axle housing with machined gasket surface
• Lightweight Grand National hubs in your choice of wheel bolt pattern
• 31 spline solid axles
• Lightweight vented brake rotors
• 2.5-inch Grand National bearings
• 24 spline drive plates
• 11.75 inch vented disc brake rotors
• All seals and hardware required for assembly of hubs and rotors

Needed to Complete:

• Caliper mounting bracket for your choice of caliper
• Complete 9-inch center section