Rear Axle Service Tips

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Ford 1935 to 48 Banjo Rear End Procedures
Disassembly

After removing the axle assembly, disassembly as follows. Unfasten the torque tube from the differential housing and slide the torque tube from the propeller (drive) shaft. Drive out the pin which fastens the propeller shaft to the pinion shaft and separate these parts. Unfasten the axle housings from the differential housing and slide off the axle housings. Scratch a mark across the joint of the differential pinion case so it may be assembled in the same position, then remove the bolts and separate the case. Pick out the differential cross and pinions, and withdraw the axle shafts from the inside of the differential case. 

Mount the differential  housing in a vise and pull the drive pinion and bearings from the housing as a unit.  Unscrew the nuts from the pinion shaft, mount the pinion in a vise and pull the bearings and sleeve from the shaft.

Inspection

The differential case should be examined for wear at the point where the backs of the pinions and side gears contact both halves of the case. If excessive wear is indicated, install a new case. If the backs of these gears are scored or show evidence of excessive wear, they should be discarded. This also applies to the pinion cross. 

If the bearing surface of the pinion shaft is worn enough to permit a loose fit of the taper roller bearings, the pinion, bearings, and sleeve should be replaced. If the wheel bearing surface of either of the axle housings is scored, badly pitted, or worn more than .010" undersize, the housing (or housings) should be replaced.

The bearing rollers should be inspected for chips, galling, or flat spots. The bearing cups should be inspected for any evidence of wear, marks from the rollers, etc.

Assembly

After pressing on the rear pinion bearing (4621)  so that it bears against the pinion head, install the front bearing (4621) against the rear bearing, being sure that the taper of both bearings are facing each other. The bearing sleeve (4616) may then be pressed into position. Install the adjusting and lock nuts (4634), with the  lock washer (4636) between them, and tighten the nuts so that the sleeve turns on the bearing cones with a heavy drag * and no end play. Lock the adjustment by bending the tabs of the washer against the side of the nuts. (* Ford spec was 12-17 inch pounds).

To install the pinion assembly and outboard bearing (4625), the differential housing must be heated to about 200 F. Before doing so, however, check to see that the shoulder in the housing is clean and free from burrs. To heat the housing, immerse its neck in boiling water (or heated oil) for about 5 minutes. When heated, install the outboard pinion bearing (4625). Then while the housing is still hot, press in the pinion assembly until the bearing sleeve (4616) is against the shoulder of the housing. This installation is made easier by coating the outer surface of the sleeve with gear lubricant.

When assembling the differential, first remove any burrs or dirt that would prevent the halves of the differential case from joining correctly. Then install the axle shaft in the right half of the case. Slip the pinions (4215) on the differential cross (4211) and lay the assembly in position in the case. The other axle shaft and the other half of the case (with ring gear attached) should then be installed, and the whole assembly bolted together securely. 

After pressing the differential bearings on the ring gear hub and on the right half of the differential case, assemble the left axle housing to the differential housing, using the proper gasket (.008 to .010" thick) between the two housings. Install the differential in the left axle housing. Then, using another gasket of the same thickness, bolt these two housings together securely. 

The differential bearing adjustment may now be checked. Two people are required for this operation. Each should turn one of the axle shafts in the same direction and at about the same speed. If the adjustment is correct, a heavy drag should be felt. If the shafts turn easily, without apparent drag, the gasket on the right axle housing should be replaced with a thinner one (.004 to .005" thick). Check the adjustment in the same manner. If satisfactory, check the backlash between the ring gear and pinion. 

The gear adjustment is obtained by increasing or decreasing the gasket thickness at the left axle housing. However, in order that the differential bearing adjustment be preserved, whatever gasket thickness is added to the left housing should be removed from the right housing. Likewise, if the gasket thickness at the left housing is decreased, the amount by which it is decreased should be added to the right housing

Backlash between the ring gear and the pinion gear should be .003 to .008", and is checked with a dial indicator mounted so that the movement can be observed at the splines of the pinion shaft when the shaft is rotated back and forth. Mount the indicator on the housing, with the button contacting the splines on the pinion shaft. If less than .003", increase the gasket thickness at the left housing. If more than .008" decrease the gasket thickness at the same housing.

Complete the assembly by meshing the propeller shaft with the pinion shaft so that the lock pin holes line up. Drive in a new lock pin and rivet the ends securely. Slide the torque tube over the propeller shaft and bolt the torque tube to the differential housing, using a new gasket between these parts. 

Reinstall the axle housing and torque tube assembly in the vehicle. Remember to secure all fasteners at all mounting points (including shock mounts, spring mounts, radius rods, transmission rear support, speedometer cable, etc). Also, remember to add the appropriate gear lubrication to the rear axle housing

         Rear Axle & Differential Housing Drawings

Typical Differential Cutaway Drawing 

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