Ford 9 Inch Posi Aluminum Case 3rd Member, 31 Spl, 3.50:1 Ratio

• A356-T6 housing with 3.062-inch carrier bearing race diameter
• Forged aluminum through bolt cap design for additional strength
• Hand-assembled by our trained technicians for an unbeatable combination of quality and value
• Track-tested durability in our own cars – we race what we sell
• Precision assembly for the correct backlash, preload, and pinion shims to ensure the correct gear pattern
• Billet steel adjuster nuts with heavy duty keepers to maintain ring & pinion settings
• Ring and pinion gears made from 8620 cold-rolled steel for long wear
• Lightweight aluminum housing has forged caps and extra beef where needed while saving 12 lbs. over cast iron versions
• Large bearing forged aluminum “Daytona” style 10-bolt pinion bearing for strength and reliability
• Spacer and shim setup maintains critical pinion depth settings and is easier to service than traditional crush sleeves
• Gear style positraction differential gives limited-slip performance and quiet operation
• Ring gears assembled with Grade 9 hardware, 15 percent stronger in tensile strength than Grade 8
• Viton® pinion seal, resistant to chemicals and high temperatures
• Grade 8 Carrier cap through bolts for additional strength
• Lock-style pinion nut with pre-applied Loctite®
• Available in both 28- and 31-spline axle options and from 3.00 to 4.56 gears
• Standard gear oil fill location on driver’s side of casting
• Includes form-fitted, reusable red poly storage case

Lightweight Aluminum 9-inch Center Section Reduces Unsprung Weight

There’s no denying that the Ford 9-inch axle is one of the most popular performance axle swaps in the history of automotive performance. Not only are there more 9-inch axles under hot rods and muscle cars than Ford ever produced, but they’re found under many a ride that isn’t even a Ford, such as first generation Camaros, C10 pickup trucks, G-body race cars, and much more. While they are known for their strength, they are also known for their weight. They are among the heaviest car-based axle assemblies known. While that does help make them strong, it also means you’re carrying around additional unsprung weight that hurts performance and handling. One of the simplest options to reduce weight on your Ford 9-inch is by swapping to a Ford 9-inch center section made from aluminum.

Using a 9” aluminum center section provides similar, if not even more strength, than traditional gray iron third members while shaving 10-12 pounds off your ride’s unsprung weight. What does that ultimately mean? For your car or truck that means quicker acceleration, better handling, and even improved braking, as your suspension and axle can respond more quickly to changing road conditions, keeping the tires in better contact with the road. Building your Ford 9-inch with an aluminum third member provides all these benefits while still allowing one of the largest reasons for running the Ford 9-inch in the first place, an easily removable Ford 9-inch case. Using the bolt in Ford 9-inch third member permits owners to swap gear ratios or differential types with ease without requiring difficult ring and pinion gear setup each time like weaker integral carrier housings require, such as GM’s 10-bolt.

Cast From A356-T6 Aluminum And Precision Machined For An Exact Fit

Using premium alloys like A356-T6 means you’re getting a precision machined cast part that is void of any porosity with exacting surface tolerances providing leak free installation and easy fitment of bearings, seals, and more to build the perfect Ford 9-inch third member for your 9-inch axle. Forged aluminum main caps, secured by Grade 8 through bolts for maximum strength that reduces gear deflection, while billet steel adjusters with high-strength locks ensure that the ring and pinion are properly meshed and stay that way.

Assembled by Our Professional Techs

Hand-assembled by trained experts in-house, our Ford 9-inch third members are built from quality components with an exact step-by-step process. We bring this combination of precision assembly and quality components to you at a price that can’t be beat. We trust these third members so much, they’re the go-to choice for our own rides, from the street to the track. Simply select the axle spline count and gear ratio desired and we’ll start assembling your custom built aluminum 9-inch center section immediately.

Proper Ring & Pinion Gear Teeth Mesh Pattern For Quiet Operation

Getting a proper pattern on the ring gear teeth is crucial. Our time-proven, step-by-step process ensures the correct backlash, preload, and proper amount of pinion shims to ensure the correct pattern on the ring gear teeth for maximum performance and minimum noise. The gears we use are cold-rolled 8620 steel, known for its long-wear and durability. We use either Motive Gear (3.00 and 3.25 ratios) or Richmond Gear (3.50 to 4.56 ratios) ring and pinion sets in our aluminum 9-inch center section builds, so you know these gears are up to the challenge.

To ensure a proper gear pattern, we use a stronger forged aluminum “Daytona” style 10-bolt pinion bearing support to maintain that critical pinion depth setting. Stronger due to its larger bearings, our Daytona pinion support also uses a fixed spacer-and-shim setup to maintain critical pinion depth settings under high load, unlike traditional crush sleeves which often compress further under load, affecting the preload setting and leading to failure. With solid bearing spacers and the proper shims, we eliminate this problem and make setting preload easy and repeatable during installation, service, and gear changes. Since preload is already set, simply torque the pinion nut to 160 ft-lb and you’re good to go. The pinion gear is connected to our new, forged steel “Ford short” 1310-type pinion yoke.

Gear-Style Posi Differential with Proven Performance 

Our Ford 9-inch aluminum third members utilize a quiet, yet effective, gear-style posi differential, providing you maximum traction. Based on the original limited-slip designs of the OEMs, these differential units provide the added benefits of experience over millions of miles and decades of proven reliability. A gear-style operation means no clicking around corners like lockers have and our posi units feature heat-treated spider gears in a forged steel case. We’ve taken this posi to the next step in performance with increased gear pressure and holding power, suiting it well for heavy-duty street car applications. For both 28- and 31-spline applications we fit the Richmond Powertrax Grip Pro differential.

Proven Reliability With Quality Hardware And Attention To Detail

We run what we sell. Our third member units are the go-to choice for our own rides, and we have built these units to last with high-quality hardware and components. Tapered steel roller bearings minimize friction, better handle thrust loads and increase load-carrying capacity. The ring gears are assembled with Grade 9 bolts with a tensile strength of 180,000 psi, a 15 percent increase over Grade 8 hardware. Heavy-duty Grade 8 carrier cap through bolts, a lock-style pinion nut with pre-applied Loctite and high-quality Grade 5 pinion support bolts makes our third member near-bulletproof.

Units include a Viton® pinion seal providing long-lasting oil and chemical resistance. This seal retains elasticity up to 399°F (204°C) and intermittently up to 600°F (316°C) This high temp seal helps eliminate pinion leaks, reduces maintenance, and keeps the third member properly lubricated. A third member-to-housing gasket and new mounting hardware is available separately.

Made to Order For Your Exact Needs

Our hand-assembled Ford 9 inch third-member assemblies are made-to-order. We keep a supply of the most popular gears in stock, with most units built within two to three days of placing your order. Our third-member units are shipped ready to install in a durable, reusable poly storage case. Not only do these shipping cases protect your new differential during shipping, but they are perfect for keeping multiple gear sets stored and ready for varying track conditions/lengths to ensure your race or performance street car is properly geared for the intended use.

Instructions (PDF)