An early Ford rearend is simple, but it takes some extra time to set it up and get the gear mesh pattern just right. This is achieved by using gaskets of differing thicknesses for the housings. With pattern paint on both pinion and ring gear, the centersection is put together, then the housings are bolted in place, and the axles installed. The axle is turned some, then taken apart again to check the pattern. If it is close, the process is repeated with thicker gaskets until the best possible pattern is achieved. If it is way off, the pinion has to be taken out and shimmed. That might happen with new rearend gears sometimes. Many doing the conversion to 9-inch axles also convert to open drive with another HRW kit, especially if a transmission other than a ’39 Ford type will be used. Ford used the same rearends in an open-drive version on some of the pickups (early F-1), but those rearends aren’t that easy to find today. The HRW kit is made for either 6- or 10-spline pinions, depending on which type a customer has.
With the rearend completed and the new 9-inch axles in place, we have a more modern, safer axle, and even with the stock gears, it can take much more punishment than the stock axle ever could!