Jaguar XJ-S. Service manual — part 98

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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,

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where xx has the same meaning as my original e-mail. Available ex-stock in pack quantity of five pieces at £3.65UK
per piece plus tax.”

Apparently there’s an easier way: just reuse the shim that came out. Everyone who’s done this job confirms that
apparently the companies that make the bearings maintain excellent control of their tolerances so you just take the old
bearings out and install the new bearings and the same shim is the one you need. Jerry Holloway says, “I spent hours
(ok, too much time anyhow) dial indicating the new bearings on the hubs in. After just a few miles of operation I could
clearly see that the original spacer would have been fine. After consulting a couple of sage Jag people (who weren't in
it for the hourly base rate) I found that using the original spacer is exactly what they had done for years, with no
problems.”

REAR AXLE FAILURE: Jan Wikström reports on his problem and solution: “The stub axle in the hub carrier (the bit
that turns in the rear wheel bearings) is splined for the hub and has a large thread and castellated nut on its outer end.
This thread comes right down to the splined part with no fillet whatever and creates a horrendous stress concentration at
the end of the thread. Mine suffered a fatigue fracture in consequence; my local parts pusher tells me this is not
uncommon, as one would expect from such an elementary error, especially if the nut is overtightened. Accordingly, I
ground and polished a shallow rounded groove at the base of the thread of the new part... (see Figure 19 and Figure
20, illustrations graciously provided by Wikström).

“The next time you do the rear wheel bearings or U-joints, I strongly
recommend having the stub axles checked and modified; any
competent engineering shop will know about stress relief.

Modifying parts of the Jaguar may be sacrilege to some of us, but
fine as the design is, it isn’t perfect...”

If the stub axle has already broken, it is possible to fix it by drilling and tapping a hole in the end and using a bolt and
washer instead of the nut. GT Jaguar (now defunct) offered a grade 8 bolt and a specially designed washer for this
purpose, and you could easily come up with suitable parts from local sources. This fix may also be used as a
preventative measure, since cutting off the stub and drilling for the bolt eliminates the stress concentration in the
original part as well as the shallow groove does.

Perhaps one thing to note is that GTJ offered these parts at all; that would seem a serious indicator of just how common
this problem is, and how important it is to address it.

Sean McKee reports that the stub axles in his 1990 XJ-S already had a suitable radius in this corner when he got there.
Apparently Jaguar addressed this problem somewhere between Wikström’s mid-70’s XJ12C and McKee’s 1990.

Figure 19 - Rear Stub Axle Failure Location

Figure 20 - Rear Stub Axle Modification

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REAR HUB CARRIER CRACKING: Joe Bunik reports that the cast aluminum hub carriers on his car had a crack in
the area just above and outward of the fulcrum shaft. The crack was parallel to the fulcrum shaft, but just far enough
above it to be in the structural portion between the fulcrum shaft bearings and the wheel bearings. What with the rough
surface on the cast aluminum combined with the dirt and grime normally covering it, it is entirely too easy not to notice
a crack like this. There are some photographs of such a crack on the WWW at

http://www.jag-lovers.org/xj-s/book/HubCarrierCracks.html

Such a crack is disconcerting to say the least, and many owners will feel compelled to order replacement parts
immediately. However, the crack in the hub shown in the pictures at the WWW site does not appear to be the result of
stress; rather than starting at an edge and working across the part as one would expect of a stress crack, it appears to
start and end in the middle of the part. It therefore appears to be a casting flaw caused by cooling the casting too
rapidly or unevenly. Subsequent reports from owners and mechanics seem to indicate that these cracks are not
uncommon and haven’t been known to result in structural failure.

REAR SWINGARM OUTER PIVOT: The connection between the outer end of the swingarm and the lower end of
the hub carrier involves a pair of tapered roller bearings. These bearings are lubricated via a grease nipple in the bottom
of the hub carrier and are sealed with a felt ring.

The design of this pivot joint allows the bearings to be adjusted with shims to be tight. When correctly assembled, they
roll firmly; there should be no slop or rattling whatsoever. This pivot joint holds the alignment of the rear wheel; any
slop means that the wheel is sloppy in which direction it aims.

REAR SWINGARM OUTER PIVOT - GREASING: The grease fitting is obvious, dead center bottom on the hub
carrier. But just what good does it do? Patrick MacNamara says, “the relief port for the grease pressure is only about
1" away from the nipple (center of swing arm about 90° around the fulcrum from the nipple facing inboard) adjacent to
the hollow end pipe of the lower arm. When cavity is full, it just vents out of the hole and fills the hollow longitudinal
portion of the swing arm and no old grease will be pumped out. The only way to get rid of the old grease is
disassembly.”

On the author’s ’83, MacNamara is incorrect. There is a cast-in boss facing inboard, but the hole in it has a bottom; it
does not open into the pivot joint area. There is a grease relief, though, just above this cast-in boss. It points upward
and inboard at about a 45° angle. It’s a 3/32” hole, completely obscured by all the dirt and grime that has accumulated
on that surface of the hub carrier. In other words, MacNamara was in error regarding the location of the grease relief,
but he was correct that it was there -- and in its effects.

You might consider plugging the grease pressure relief port. A 1/4” long #4 self-tapping screw will work nicely -- two
per car. This will at least help keep dirt and water out.

If you plug the relief port and then use a grease gun to force grease in there under pressure, it’ll push against the felt
seal. Will it ooze through the felt seal? Maybe; at least, any air in the area will push through the felt. Hence, you
might actually achieve some beneficial lubrication with the grease gun. I wouldn’t count on it, though; you’re still not
likely to improve the lubrication in there without disassembly.

If you install oil seals as suggested below and plug the grease vent and then force grease in there with a grease gun,
you’ll probably destroy the oil seals. Your chances are a little better that the grease will just push past the seals if you
install them backwards as Ron Moore suggests, but not much better. If you feel compelled to use the grease gun, you
might be best advised to remove the vent plug first, then put it back in when done.

Better idea: Richard Dowling reports, “Of all the 24 bearings in the IRS and diff I only had 4 bad ones, namely the
outer fulcrum tapered rollers. There was plenty of grease in the bearing cavity, but that around the bearings themselves
was pretty old since the new grease goes in the zerk and out the vent next to it.

“In my stripdown I put 2 zerks in for each wheel hub to force grease through the bearings, and a vent hole on the outer
side of the fulcrum bearings to ensure grease from the central zerk can exit only after going through those bearings. All

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this is dead easy when the whole shooting match is cleaned up and on the bench. What about the fulcrum area on your
car which is probably like my XJ6, not giving any trouble, but a future concern?

“When I had my XJ-S fulcrum stripped I measured all the items accurately and made an Autocad file (see Figure 21)
of the bearing area. From that I could see a possibility of drilling a small hole through the standard assortment of
spacers and felt seals into the area next to the bearing race to make a vent, all without stripping the assembly. This
morning I tried it on my XJ6 and it works.

3mm

DRILL @ 65deg TO SHAFT CENTRE LINE
START @ 3mm FROM FACE OF HUB CARRIER

SEAL RETAINING CUP

FELT SEAL

DRILL APPROX 2.5mm DIA.

SHAFT

Figure 21 - Rear Outer Pivot Grease Vent

“You take the wheel off, and drill a hole about 2.5mm diameter starting at 3mm from the machined end of the alloy
casting. The drill must be at an angle of 65deg to the centreline of the 5/8" shaft running through the bearings. The
3mm and 65deg are moderately critical. I drew an angle of 65deg on a piece of paper and put it under the hub to give
me a guide as I drilled.

“On the first one I broke the drill because I was in a hurry. You drill about 5mm though alloy then you hit the mild
steel cup that backs the felt seal. You go through the first face of that cup which is parallel with the shaft since it fits the
bearing bore, then you hit the felt seal and a little further on you hit the return face of the cup which is at 90deg to the
shaft centreline. This latter face is hit at an acute angle of 25deg which is where I broke the tip off my drill. If you
exercise patience and take about 5 or 6 minutes to drill each hole, backing off as you break into the felt seal, then going
carefully for that return face, it is no problem. Total drill depth is around 12mm.

“As soon as I thought I had broken through I put my grease gun on the zerk and tried it. That also pumps out the swarf.
In any event, looking at the pounding on my XJ-S bearing, a small piece of swarf most likely would make no
difference. However, if you grease the thing every 6 months you are pumping grease in a direction that takes the swarf
out of the bearing - that will be the least of your worries.