387
Figure 19. From the U-joint outward, the items held tightly by the nut are: The inboard oil seal track, a shim
CAC3818, the hub, and a washer under the Jesus nut itself.
Notice that I did not mention any bearing races! The inner races of the bearings fit around the outside of the hub and
are not compressed by the Jesus nut. The inner race of the outboard bearing is press fit while the inner race of the
inboard bearing fits more loosely over the hub. When the nut is torqued down and pulls the stack tightly together, the
space between the inboard oil seal track and the inner race of the outboard bearing is supposed to be exactly right to
position the inner race of the inboard bearing to provide .001-.003” of end play. The shim is selected accordingly; the
thinner the shim, the tighter the bearings get.
Note that the inboard oil seal track actually serves more purposes than simply as a seal track. It has a large chamfer on
the ID on one side to clear the radius on the stub axle between the shaft part and the yoke part. And it also provides a
flat surface that the shim is tightened against. The shim is tightened against the innermost portion of this flat surface,
while the outer portion has the inner race of the inboard bearing butted up against it.
All of which led to the problem that Sean McKee ran into. Since the inner race of the inboard bearing is not securely
clamped, it was apparently free to rotate in his car. As it rotated around the hub, it wore away the surface of the inboard
oil seal track. The flat face of the seal track was no longer flat; it was unaffected at the innermost area where the shim
was tightened against it, but the outer area was worn back several thousandths creating a circular step in the surface.
That isn’t all it created; it created a quarter inch of play at the top edge of his rear tire! Having the step in the face of the
seal track loosened up the end play adjustment, allowing gobs of slop. The protruding unworn inner portion on that
face is just like having a shim that’s too thick. He found the same problem on both sides of his car, so it probably
wasn’t a fluke.
The fix is obvious: replace the inboard oil seal track. Perhaps less obviously, you can fix the problem by simply
grinding the face of the old inboard oil seal track flat again. McKee reports that the seal track didn’t seem especially
hard, as though Jaguar didn’t expect that inner race to rotate.
Less obviously still, you could grind the old inboard oil seal track flat and then install an arbor shim in front of it. The
ID and OD of the arbor shim would need to be the same as the seal track itself. The whole point of doing this is that,
hopefully, the arbor seal will be made of something much harder than the seal track and hence won’t wear as quickly.
It doesn’t really matter how thick the arbor shim is; it won’t affect the bearing adjustment. However, any such playing
in here -- replacing the inboard oil seal track, grinding on it, adding an arbor shim -- should be followed by an
alignment job on the rear end of the car, as this all may affect the camber.
The part number for the inboard oil seal track in the 1987 Parts Catalogue is C.15232, but McKee says there’s
apparently a later part number CCC6807. Perhaps Jaguar made the part harder to resist wear!
By the way: if you actually expect that oil seal to seal against oil leakage, you’ll want to apply sealant between the
inboard oil seal track and the stub axle at assembly. Otherwise oil could sneak out along the surface of the stub axle
itself, bypassing the oil seal entirely. Of course, what’s in here is grease, not oil, but it still makes a mess when it gets
out.
Regarding selecting the shim: The ROM describes trial-assembling the hub with tool JD.15 and carefully measuring
the end play and subtracting to determine the shim you need for final assembly. The tool is effectively a fat shim,
which means you can skip buying the tool and just buy a fat shim. Using the stub axle for this trial assembly may be
inconvenient, but you can just use a section of threaded rod with some nuts and washers.
So, after all that fiddling, you finally get to put the shim on order! If you don’t want to wait on shipping, you can either
order an assortment of shims before starting or you could just order one really fat shim (you may have already!) and
take it to a machine shop and have it milled to final size when you determine what size you need. Mike Morrin says, “I
was unable (despite repeated attempts) to buy spacers from the local dealer, so got some sent out from the UK.”
Craig Sawyers says, “The shims (they look like either brass or bronze) are stock items. Part number CAC3818/xx,
where xx is the number of thou plus 0.1 inch (so if xx was 14, the shim thickness would be 0.114 inch). Price in the
UK is £3.70 each plus tax off the shelf. They are available in 2 thou increments (ie xx is always even), consistent with
setting an end float of 2 thou.” Sawyers provides a later correction: “The part number has changed to CCC6806/xx,