Ford 9 Inch Limited Slip Posi Differential Third Members, Helical

Assembled by Professionals

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.

Tough, Nodular Iron Center Section

Our Ford 9 Inch Nodular Iron Third Member Center Section Carrier starts with a NEW casting with over 4 lbs. of additional material in critical areas. Nodular (ductile) iron is much more resistant to fracturing than OEM “gray" iron. Extra ribbing reinforces the case and rearmost pinion support (pilot bearing).

Thick, forged steel bearing caps surround the carrier bearings, all securely held in place with precision Grade 8 cap screws. The improvements continue with rugged billet steel adjuster nuts and heavy-duty keepers to ensure your ring gear settings are maintained. All mounting surfaces are precision machined to ensure a consistent, flat surface for a positive gasket seal (no more leaks on your shop floor). An oil fill plug is included.

Precision Assembled for Proper Ring Gear Teeth Pattern

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. Our gears use use cold-rolled 8620 steel, known for its long-wear and durability.

To ensure a proper gear pattern, we use a stronger “Daytona" style pinion bearing support to maintain that critical pinion depth setting. Stronger due to its larger bearings, our Daytona pinion support also uses the spacer-and-shim setup to maintain critical pinion depth settings under high load, unlike traditional crush sleeves which often compress further, take out your preload and lead 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./lbs. and you’re good to go. The pinion gear is connected to our new, forged steel “Ford short", 1310-type pinion yoke.

Note - Speedway Motors Differential 3rd members come with a 1310 Universal Joint (U-Joint) series yoke. No other Yoke size options are available. 

1310 series U-Joint and Bearing Cap Reatainers Not Included - Sold Seperatly

Helical-Gear Style Differential

Our helical style limited-slip differential works with any factory Ford 9 inch differential case, gear, axles and bearings. The helical-gear design gives quiet operation, with no clicking when disengaging for corners. While under normal conditions the helical-gear style performs like an open differential, when required the differential automatically transfers torque to the wheel with the highest traction. Smooth power transfer is unnoticed by the driver.

When you want the traction benefits of a limited slip differential in your Ford 9 inch rearend without the expense and noise of a full-locker unit, our helical style differentials are just the ticket.

Proven Reliability

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% increase over Grade 8 hardware. Heavy duty Grade 8 carrier cap bolts, a lock-style pinion nut with pre-applied Loctite and high-quality grade 5 pinion support bolts make 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 carrier-to-housing gasket is available separately.

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 2-3 days. Our third-member units are shipped in a durable, reusable poly storage case, perfect for keeping multiple gear sets stored and ready for the track.

Features

• 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 proper amount of pinion shims to ensure the correct pattern on the ring gear teeth
• Ring and pinion gears of 8620 cold-rolled steel for long wear
• Nodular iron housing is stronger than OEM “gray" iron and has 4 lbs of additional reinforcement
• Large bearing “Daytona" style pinion bearing supports for strength and reliability
• Spacer and shim setup maintains critical pinion depth settings and easier to service than traditional crush sleeves
• Helical gear differential gives positive traction without the noise of a full locker
• Ring gears assembled with Grade 9 hardware, 15% stronger in tensile strength than Grade 8
• Viton® pinion seal, resistant to chemicals and high temperatures
• Grade 8 Carrier cap bolts
• Lock-style pinion nut with pre-applied Loctite®
• Grade 5 pinion support bolts
• Includes form fitted, reusable red poly storage case
• Choose gear ratio - 3.25, 3.50, 3.70, 3.89, 4.11, or 4.56
• Choose axle shaft spline count - 28 or 31 splines

3rd Member Instructions (PDF)