Post
by angelw » Tue May 12, 2026 10:42 am
Hello Geoff,
The Type 3 differential used a double row, angular contact ball bearing race, with split, two piece inner race. When assembled and held together by hand, there is a slight gap between the inner faces of the inner race halves. When pushed together via the securing nut, the two halves are pressed together until the inner faces are in interment contact, and that point, the bearings are in correct pre-load.
Unfortunately, these bearings made by Hoffman, haven't been available for many years, and I would be surprised if Alan has any. The alternative offered by SNGB and others is a very poor replacement. It's a double row, angular contact bearing of the same ID/OD, , with a solid, one piece inner race, and therefore, no scope for pre-load. They are 2mm narrower than the original, which requires a 2mm spacer ring for both the inner and outer bearing race. The spacer for inner race is located concentric by its bore being a close running fit on the axle, but SNGB supply a spacer for the outer race that has the same OD as the bearing, which is wrong.
There is no amount of available bore for this spacer to be located concentric with the bearing, and as the spigot bore outboard of the bore for the bearing, where the outer bearing spacer is located, once the nose of the bearing retainer plate, come brake caliper bracket, starts to enter its spigot bore, sight and control of the spacer is lost, where it can then fall to the bottom of the spigot bore, unless the spacer is held concentric with the bearing with grease, or glued in place with bearing retainer. A more sensible solution would be to make the OD of the outer race spacer a slight running fit in the spigot bore. However, even with this spacer being located concentric with the bearing, there is still no pre-load of the bearing.
Later differentials, starting with Series 3, perhaps Series 2 XJ6 cars, and other models circa that time, the output shaft bearings system reverted back to that used with the Type 1 and 2 Salisbury differentials, that being opposing taper roller bearings. The angular contact bearing, with the built in pre-load would have been introduced for expedience sake in assembly; you simply torque the securing nut to press the halved of the inner race together with no further adjustment. The opposing taper bearings isn't an inferior system, in fact, it would be arguably better when sharing axial and radial load.
Given the poor alternative to the correct Hoffman bearing, if the output shaft bearings have to be replaced, it would be better to convert the differential to use the Taper Roller Bearings. The taper roller bearing and shaft assembly is entirely interchangeable with the angular contact bearing system without modification to the differential housing. New parts are not available, therefore, you have to find the parts from the later model differential. New parts not being available is not entirely correct, for I manufacture the bearing housing/brake caliper bracket as a new part, and supply the output shaft on an exchange basis. There is a "metal on" condition of the angular contact bearing output shaft, that allows for it to be re machined to the specifications of the taper roller output shaft.
Regards,
Bill
