Choosing Parts for Your Ford 9" Third Member Build

The Ford 9” is arguably the most popular rear end of choice for hot rodders and racecar builders alike. With its' proven durability and huge aftermarket support, a bulletproof rear end can be achieved by selecting the correct components for your application. Whether you are having a custom rear end built from Speedway or building your own at home, making sure the parts inside your 3rd member work together is crucial.

Carrier Housing: The carrier housing is the main part of the 3rd member. Ford began manufacturing these in 1957 for use in their light pickups and cars. Since they haven’t been produced by Ford since 1986, sourcing a good, viable housing has become extremely difficult. Speedway Motors offers a wide selection of completely new manufactured carrier housings.

Here are a couple of things to consider when picking out the carrier housing:

Bearing Size: The 3.062” diameter bearing caps are the most common size. A 28 or 31 spline spool or differential can be used. Speedway also has a carrier with 3.25” diameter bearing caps. These carriers are usually used on high horsepower applications, such as drag racing. With the larger bearing caps, a typical 28 or 31 spline spool or differential can NOT be used, as these are designed for use with the larger 35 to 40 spline applications.

Material: A cast iron version as well as a lighter weight Aluminum version are available. The aluminum case weighs 20 pounds less than the iron version, and the strength is about the same. The lighter weight case does add some cost to the housing, but if you are looking for an easy way to remove around 20 pounds, this is a fast and affordable solution.

Our most commonly sold carrier housing is part number 91048398, which is the Cast Iron Housing with the 3.062” bearing diameter. This is also the carrier used in all of the 3rd members built at Speedway, unless you specify a different case to be used, which we are happy to do.

The only pinion supports we use when we build 3rd members is the Daytona style pinion support with a larger inner bearing and better oil passages. It is all around better than the typical factory Ford pieces.

Gear Set:

Picking out the proper gearing for your application is a topic that should be best left to your own research. There are many calculators online that can be used to help determine the proper gear ratio.

One of the many services we provide, whether you are buying just the gear set from us, or having a complete 3rd member built, is the Ring Gear Lightening, part # 91600013. On a 5.43 ring gear, 2.6 pounds of material is removed, without compromising the strength of the gear. The amount of weight removed is determined by the gear ratio. A higher gear ratio, such as a 6.33, will see much more material removed than a 4.11 gear due to the way ring and pinions are manufactured. As the gear ratios go higher, the pinion gear shrinks in diameter, so the ring gear is made thicker. On a dirt track car, if a lightened spool is used to reduce the amount of rotational weight, a lightened ring gear will aid in additional benefits of being able to turn the wheels quicker.

I personally recommend never using a factory type crush sleeve when setting up the pinion. A Solid Pinion Bearing Spacer Kit with Shims such as part # 9190920, is a much better solution. The problem with a crush sleeve is if you ever drop a driveshaft, the gears in the rear end can get destroyed. Every 3rd member we build is built with a solid spacer. This provides cheap insurance that your rear end will survive when a crush sleeve would lead to destruction.

The Ford 9 Inch Econo Ring & Pinion Set-Up Tool Kit, part # 91082720, includes the tools you need to lock the pinion in place during assembly, as well as setting the correct gear backlash. You can also pick the components you want, and have Speedway Motors do all the work for you and build a third member exactly to your specifications.

Lubrication:

One of the most important items for long life of the rear end is proper lubrication. We recommend using Lubrication Engineers SAE 140W Gear Oil, part # 91044140, for racing/extreme applications, and the 90W Gear Oil, part # 91044090, for street use and daily drivers.

For race applications, it is required that a full 4 quarts are used, or pinion failure will occur. The factory fill plug will begin to overflow before the full 4 quarts is in, so the rear end housing must have a fill plug at the top of the housing.

This gear lube also serves as a great assembly lube when assembling the 3rd member. It is thick and stays on the bearing surfaces to make sure no metal on metal contact happens on those first few miles. This is what we use here at Speedway during the assembly process.

If you still aren’t certain what components you should pick, our Race and Hot Rod techs are just a phone call away and will be able to assist with any questions.