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How to Measure and Cut 9 Inch Ford Axles

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There’s no denying the popularity of the Ford 9” housing. Over the last half century, they’ve proven themselves to be strong and easy to work on and they’ve ended up under countless hot rods, muscle cars, and even drag and circle track race cars. This popularity has led speed shops like Speedway Motors to offer housings to fit just about any application you can dream up. This means that there are almost infinite different widths out there. How do you get axles that will fit? Here’s where the popular cut to fit axles come in. In this video, we’re showing our preferred method for measuring and cutting 9” axles.

How to Measure

The important takeaway here is to note that there is not a standard formula that says what axle length is appropriate for what housing width. There are obvious variables with housing/bearing type, but also variables in the differential. Different types will require slight differences in axle length. So, our method involves assembling the third member to the housing, then measuring to the bearing surface. This method will account for these slight differences. Another important note is to pay attention to which axle goes in which side. In most cases, the short axle goes in the driver’s/left side.

In the above video, you’ll see us installing the axle, then measuring out to the end of the bearing. You can also stick a tape measure into the axle tube and measure to the stop in the differential. As we measured, we did not account for the thickness of the backing plate. This was intentional. You want to leave a little room between the end of the axle and the stop in the center section. Believe it or not, these axles actually twist under power, growing and shrinking slightly as they do. You want to leave a little room to do so, and that 1/16” of an inch or so seems to work well.

How to cut

We used a horizontal bandsaw. If you don’t have one in your shop, any means of cutting will do. Just be sure to keep your cut square. You’ll also want to use a file and/or a grinder to put a little lead-in on the end of the splines and dress up any burrs that remain.

Be sure to test fit before installing the backing plate or retainer. You should feel the axle slide into the splines well before the bearing seats. You should not feel the axle bottoming out against the pin in the differential before the bearing seats. You may also choose to double check your measurement with a tape measure.

This is not a difficult process. Just remember that every application is going to be slightly different. Speedway Motors offers axle assembly kits with all the hard work done for you, but if you’re building up your 9” piece by piece, be sure to measure carefully with the third member installed before ordering your axles.

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