[5] When the machined parts...
[5] When the machined parts came back from Hot Rod Works, the differential housing and the ring gear had been machined (arrow) for the new larger axle gears.
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.
[6] Here the axle gears are...
[6] Here the axle gears are in place. The splined inner ends of the new axles will locate inside them.
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!
[7] When the centersection...
[7] When the centersection is put together with the new gears it includes the four original type 11-tooth (1938-48) spider gears in the differential. Next will be the differential housing cover with the second new gear, which is bolted together on the ring gear with the eight long bolts.
[8] The complete differential...
[8] The complete differential is in place and tightened down, then secured by cotter pins.
[9] The pinion is dropped...
[9] The pinion is dropped into the centersection with new bearings, after the housing had been heated in an oven and the pinion cooled in a freezer.
[10] The ring gear and pinion...
[10] The ring gear and pinion are marked with a special paint marking for the pattern test. New bearings have been pressed onto the outer ends of the ring gear and differential housing.
[11] The gear mesh pattern...
[11] The gear mesh pattern can be tuned by using gaskets of differing thicknesses between the centersection and the axle tubes. If that isn’t enough the pinion has to be removed from the centersection and shimmed or machined.
[12] With everything in place,...
[12] With everything in place, it’s time for the second housing to be bolted on.