9" Ford Third Members | Custom Built Ford 8 and 9 Inch Rears

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Limited-slip differentials, specifically 9" third members, can be used for both street and race applications. They are offered in a variety of cases - standard, nodular, and aluminum thru-bolt - to suit different needs. Any of these Ford rear differentials can accommodate 28, 31, 35 or 40 spline axles.

Each third member includes a new housing gasket and is equipped with a friction modifier for trac-lok units. All third members contain either Motive, US gear, or Strange gears.

Our standard case and pinion support option includes both a used case that has been cleaned, glass beaded, and painted, as well as a brand new case. In addition, all internal parts such as bearings, seals, o-rings, crush collars, and nuts will also be new. The carrier and gears are also newly installed. Customers have the choice of a new Billet Trac-Lok or Eaton True-Trac to complete their setup.

Introducing our high-quality nodular case, which comes equipped with the latest Daytona pinion and an array of new internal components such as bearings, seal, o-ring, solid pinion spacer, and nut. As for the carrier and gears, you can expect them to be brand new as well. Plus, we have various options for differential types including a Billet Trac-Lok, Eaton True-Trac, or Detroit Locker.

The nodular case, marked with an external "N," will come equipped with a properly fitting C5 Daytona pinion support. It has been refurbished and includes all new internal components such as bearings, seal, o-ring, solid pinion spacer, and nut. The carrier and gears are also brand new. You can choose from our stock trac-lok, new Billet Trac-Lok, or Detroit locker options. Our inventory of casting dates regularly changes. This particular nodular iron case was standard in GT-E's, 428 Cobra Jets, 429 Cobra Jets, Boss 429 Mustangs, Boss 302 Eliminators and Boss 302 Mustangs. 

The nodular case did not feature the external "N" marking until October 31st of 1968.

The Trac-Lok is a clutch type differential, and comes with Friction Modifier for optimal performance. It operates smoothly and quietly, making it well-suited for street use. Similarly, the Eaton True-Trac also boasts a quiet experience on the streets, and is particularly recommended for road racing. The Detroit Locker, on the other hand, is a mechanical clutch type differential that can be quite aggressive on the street. However, this may result in increased noise while turning, as it unlocks when one wheel turns at a different speed than the other.  All types of carriers, including differentials, function in the same way. Limited slip and posi are essentially identical.

For proper installation of a third member that can easily be fitted into your car, we will require the specific yoke information for your vehicle.

There are a few options to consider when taking measurements for your pinion seal and yoke. You can measure from the face of the pinion seal to the face of the yoke, and choose between two lengths: 3 ¼” (short) or 4 ¼” (long). Similarly, when measuring for width, you can either measure the universal joint or the space between tabs in the yoke. In this case, there are two choices: 3 ¼” (narrow) and 3 5/8” (wide). Lastly, to determine your u joint bearing cap size, you will need to measure the diameter of the u joint caps. There are three sizes available: 1 1/16”, 1 1/8”, and 1 3/16”.