CHANGES IN TRUCK REAR AXLE

To still further increase the strength and wearing qualities of the truck rear axle several improvements have recently been made.

The method of grinding the rear axle shaft has been changed to improve the fit in the hub. This change in the grinding cannot be noted by visual inspection.

The rear hub and drum assemblies are changed by removing the undercut from the center of the taper, moving the keyway in line with the lubricator fitting boss, and improving the heat treatment on the hub sleeve.

The rear wheel bearings have been re- designed. Two combination spiral and solid type roller bearings are now being used in each hub instead of one long spiral roller bearing (see Fig. 1155).

Before installing a new axle shaft in a customer’s truck, the tapered hole in the old hub must be accurately checked, as it is absolutely essential that the hub have a full bearing on the shaft. The checkup is made as follows:

See that the new shaft and old hub are absolutely clean and free from burrs, then using ,the new shaft as a plug gauge, place a very light coating of Prussian blue around the entire tapered end of the shaft. Insert the shaft into the tapered hole in the hub and turn the shaft back and forth several times. Next withdraw the shaft and check the bearing in the hub. If a full bearing is not shown, it will be necessary to install a new hub and drum assembly, checking the new hub in the same manner.

When installing the hub and drum assembly, be sure the axle shaft key is in place; then force the hub all the way up on the
shaft. A piece of heavy tubing (thick wall), the inside diameter of which is slightly larger than the threaded end of the shaft, can be used as a driver. A six pound brass hammer is used in forcing the hub on the shaft (see Fig. 1156). After hub is installed on shaft, see that the flat washer is in place on shaft securely tighten axle shaft nut and lock it in place with cotter key. Also instruct the owner, that after the truck has been in service for approximately 100 miles, the axle shaft nuts again be tightened. This is very important.

The new design hub and drum assemblies and the new design wheel bearings are to be used in all service replacements on dual wheels. Any stock of the former type wheel bearings (AA-1225-C) may be used on single wheel trucks.

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