Jaguar XJ-S. Manual - part 88

 
 

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about Jaguar’s materials engineers.  The crud must be removed to allow the spring and lower spring cup to seat 
properly. 

The transmission must be jacked all the way up into the tunnel before the spring support is installed.  Once the spring 
support is securely bolted into place, then the jack can be lowered, allowing the transmission to sit on the spring and the 
center post to protrude through the bottom. 

Easier said than done, of course.  With the transmission jacked up hard against the tunnel, bolting the spring support in 
place may still be difficult.  Paul Hackbart came up with a nifty solution, but you need to have one of the better floor 
jacks to do it:  “Larger jacks have a removable/floating circular dish piece that raises the car.  Well (Dummy!) simply 
remove disk leaving 3/4-1" hole. The long bolt goes straight through the hole as the mount is jacked/pressed up and is 
perfectly balanced allowing you to tighten all 4 mounting bracket bolts.  So, allow one jack and 2x4 to hold up tranny 
under sump and your larger one with dish removed exposing hole to jack up mount.” 

Once the spring support is bolted in and supporting the tranny and the jacks have been removed, the assembly of the 
parts on the center post is as follows: the first item to be installed should be a special washer that has rounded edges, 
C29011; it will need to be crammed into the rubber bushing somewhat.  Next is the sleeve, C30157.  Third is a part that 
looks like two washers welded together; it should be installed with the larger opening facing upward.  Then the tie plate 
is installed, followed by the large self-locking nut; there is no washer directly under the nut. 

If the special washer C29011 is missing, a 1/2” splitring lock washer bent flat will serve. 

Two small spacers should be installed between the tie plate and the forward bracket.  If they are missing, 3/8” washers 
totaling 1/4” in thickness may be used. 

After assembly, there should be no more than 3/4” between the tie plate and the bottom of the spring support.  Check 
that the transmission moves freely on the mount; since the spring is soft, you should be able to bounce the entire 
engine/transmission assembly up and down a little with your hands.  If it appears to be immovable, something is not 
right.  It also should not clunk when moved. 

Gerry Halpern had a howling noise coming from the transmission area on acceleration. “I got a copy of the assy 
drawing from a local parts guy and reinspected it again this weekend, frankly hoping to find somthing that I had 
installed incorrectly.  Alas, I couldn't find a thing wrong.  Laying there on my back looking up at the trans mount I 
pushed upward to make sure that I got movement; sure enough, it seemed to move OK.  However, I decided to loosen 
the 4 bolts holding the mount, then moved the trans up and down.  I could see the mount move and realign itself.  
Voilà!  I could now move the trans quite freely up and down.  I tightened the mount bolts and sure enough problem 
solved.  Point to be made is that the trans mount should be positioned so that the mount can be moved easily up and 
down against the spring pressure.  Two of the bolts are awkward to get at with the exhaust in place and there is a great 
deal of tolerence in the bracket slots making it easy to misalign.” 

Keeping in mind that the engine/transmission is entirely supported and positioned by the two motor mounts and the 
transmission mount, misalignment of the transmission support might be due to problems with the motor mounts.  If the 
transmission support doesn’t wanna line up, maybe the thing to do is loosen the motor mounts and see if you can 
realign them. 

 

VARIATIONS:  On page 49 of the Haynes manual, there is a picture labelled “49.5A Aluminum spigot bolted to 
transmission” (all the photos in the Haynes manual reflect parts from a Daimler Double Six with a GM400 
transmission, obviously pre-1985).  The post shown in Figure 16 is steel, so if this spigot is really aluminum it’s 
something different.  It also appears to have the entire external shape of the post incorporated in the post itself, so 
there’s no need for a “special washer” or a sleeve.  Mike Morrin says, “The GM400 mount in the pre-H.E. parts book 
shows the spigot with the ridge machined into it, there being no part numbers for the "special washer" or sleeve.”  If 
that’s actually the case, the reassembly instructions above are correct except that you can leave the special washer and 
sleeve out of the order.  On the other hand, maybe what you really want to do is find the later design steel post; it’s 
unlikely the design was changed without a good reason. 

 
 

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Sometime in the 90’s, the post design was changed again.  This final configuration had the external shape of the early 
aluminum post so no special washer or sleeve is needed, but it is made of steel. 

Paul Hackbart says there also may be a difference between the way the steel posts are constructed.  They all consist of a 
steel shaft pressed into a cast aluminum base, but some have a set of splines visible around the edge of this press fit.  
This may reflect a problem with the shaft breaking loose and turning while the mechanic was trying to tighten or loosen 
the self-locking nut -- but it’s also possible that all post assemblies have splines and it’s just that some extend up far 
enough to be visible. 

 

TRANSMISSION MOUNT SUBSTITUTION:  If you simply cannot figure out how to get the transmission mount 
back together despite all the guidance above, there are ways to substitute a more simple and basic mount scheme.  
John’s Cars (page 715) offers a “no-nonsense” transmission mount, but you might not even need that; Chad Bolles 
says, “The extension housing for the Turbo 400 in your car is nothing but a Chev part.  On my car I removed all the 
nuts, bolts, brackets, and the rest of the crap.  I went to Parts America (Western Auto) and found a rear mount that fit a 
Buick, had two (2) holes in it and one stud.  I then made myself a new rear crossmember, and reassembled the whole 
deal.  Now I can change trans fluid without removing the rear mount.” 

Of course, Jaguar didn’t provide such an involved mount scheme for nothing.  One of their reasons was that a spring 
absorbs vibration better than a block of rubber.  Imagine, if you will, how well your car would ride if you took the 
springs out of the suspension and replaced them with big blocks of rubber.  Dan Jensen says, “I cannot comment on the 
GM 400 mount offered by John's Cars.  I can comment on the effect of a TH 350 in my '83 XJ6 with the John's Cars 
rear transmission mount for this unit.  There is noticeably more vibration transferred to the car.  While John's claims 
this should not be the case (transmission the cause?), I prefer the factory mount.”  Other owners, however, claim they 
cannot feel any degradation in smoothness with the John’s Cars mount -- perhaps because their original mount was 
assembled incorrectly!  We’ll never know for sure; you’ll have to take your own chances if you decide to go this route. 

 

 

DRIVESHAFT 

 

SLIP JOINT ALIGNMENT:  Craig Sawyers suggests that when removing the rear suspension, it’s easier to just yank 
the drive shaft apart at the slip joint than to unbolt it from the final drive unit.  “There is a pair of arrows stamped on the 
two halves so you get the splines aligned and end up with a balanced driveshaft.  Both halves are balanced dynamically 
at the factory.  The arrows are faint;  I marked mine before disassembly, before I noticed the arrows after cleaning it 
up.” 

 

UNIVERSAL JOINTS:  The XJ-S was clearly not designed with ease of servicing the forward drive shaft U-joint in 
mind.  Applying a grease gun to the zerk fitting, as well as removing the drive shaft itself, require the transmission 
mount to be removed; if you have it out anyway, you may wish to address the drive shaft.  However, drive shaft 
inspection also requires that the main support plate be removed.  Jaguar provided two bolts up within the tunnel to 
make sure this task was as unpleasant as possible. 

According to Chad Bolles, the U-joints in the drive shaft are a GM standard, and Spicer 5-153X or Tru Cross 153 will 
fit.  The U-joints in the rear axles are also a standard; Spicer 5-160X or Tru Cross 160 will fit.  All of these should be 
available at your local auto parts store. 

Some mechanics claim that having a grease fitting on a U-joint does more harm than good.  In theory, if the seals in the 
U-joint are any good, it will never need regreasing; if the seals are bad, regreasing won’t help for long.  And 
undisciplined use of a grease gun is the best way to destroy the seals.  Even if you’re careful with the gun, it’s more 
than likely that the grease injected will all go to one bearing and leave the other three ungreased; it’s a path-of-least-

 
 

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resistance kind of thing.  If you believe all that, you might as well choose replacement U-joints that have no zerk 
fittings and save a couple bucks. 

 

FLANGE BOLTS:  The flange bolts are occasionally found to be loose.  Craig Sawyers:  “Yup.  Par for the course.  
However, the 15000 mile service for the car says "Check tightness of propshaft coupling bolts", so Jaguar obviously 
recognises that they loosen.  Actually, I think it more likely that the bolts stretch slightly.  While you're under the car, 
check the ones at the other end (gearbox).  Betcha they're loose too.” 

It’s also very important that the self-locking feature of the nuts is in good order.  These bolts are too short to attain any 
sort of anti-rotation action due to bolt stretch, and lock washers aren’t used here.  If the nyloc nuts turn too easily on the 
bolt threads, replace them. 

 

 

FINAL DRIVE

 

 

REAR SUSPENSION/DIFFERENTIAL REMOVAL:  It’s discussed on page 383. 

 

DIFFERENTIAL TYPES:  The XJ-S has apparently been fitted with at least two different differentials (“final drive 
units” for you Brits).  From 1976-1985, the differential was a Salisbury 4HU Powr-Lok that came with either 3.07:1, 
3.31:1 (1976-1982), or 2.88:1 (1982-1985) ratios. 

From 1985-1987, a 2.88:1 Dana unit was used. 

Now, follow closely.  From 1987 to 1993, the XJ-S was fitted with a GKN Power Lock differential with a 2.88:1 ratio.  
The 87-93 differential is essentially the same item as the pre-85 differential (a speedometer sender was added; see page 
590).  According to Richard Griffiths, in the meantime Salisbury had been bought out by GKN.  Later, GKN was 
bought out by -- wait for it -- Dana!  But this was apparently after the XJ-S changed to outboard brakes.  Dana 
(

http://www.dana.com/

) grew to be a huge corporation with annual revenues in the billions. 

In this book, we will use the same convention that is commonly used among Jaguar owners: the pre-85 unit and the 87-
93 unit will be referred to as a “Salisbury”, regardless of whether it was actually made by Salisbury or GKN.  The 85-
87 unit will be referred to as a “Dana”. 

From 1993 on, the entire rear end of the XJ-S changed.  A suspension similar to that on the XJ40 was used, with 
outboard brakes rather than inboard.  Along with the engine being enlarged to 6.0 litre and the fitting of the 4-speed 
GM 400, a 3.54:1 final drive was used. 

Apparently the AJ6-powered XJ-S’s, 3.6 or 4.0 litre, all have 3.54:1 final drives. 

All XJ-S differentials are “limited slip”, although the feature has often been given different names. 

The official Jaguar service department repair procedure for final drive units is to replace them as a whole. 

 

SALISBURY VS. DANA:  Differences between the Salisbury and the Dana include: 

ƒ  On the Salisbury, the bearings on the output shafts are held in the case with five bolts.  On the Dana, the bearings 

on the output shafts are held in place with three bolts. 

ƒ  The Dana has no drain plug. 

ƒ  The input flange on the Salisbury is circular.  The input flange on the Dana is rectangular. 

 
 

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ƒ  With the Salisbury, the inboard brake calipers are bolted to lugs on the flanges holding the output shaft bearings, 

with the bolts installed from the inboard side outward.  With the Dana, the inboard brake calipers are bolted to 
bosses on the case itself, with the bolts installed from the outboard side inward.  In order to access those bolts, the 
Dana is fitted with brake rotors with access holes. 

ƒ  The limited slip internals of the Salisbury are the “disc type”, while the limited slip parts of the Dana are the “cone 

type”. 

Greg Wells of Coventry West says the gears from a Salisbury will not fit the Dana case. 

 

DANA QUALITY:  The Dana unit has a bad reputation.  Apparently, the lack of a drain plug and the fewer bolts on the 
output shaft bearings gave an initial impression that it was “cheap”, and Jaguar’s return to the Salisbury unit after three 
years convinced many that there was something wrong with it.  However, there’s no telling what supply problems 
Jaguar was dealing with in the mid-80’s, especially with a buyout going on at Salisbury, so there may be other 
explanations for the flip-flop. 

Apparently, the real problems with the Dana are not in mechanical shortcomings in the unit itself, but rather in support 
and maintenance.  Ian Hissey says, “I have just removed the Dana diff from my XJ-SC, and replaced it with an 
overhauled Salisbury.  A number of reasons, including changing from 2.88 ratio to a 3.31 ratio, but also, here in Aus 
the cost of replacement bearings, etc., for the Dana was extortionate, more than double the Salisbury, and also the Dana 
is not a true limited slip, has a cone arrangement, which is not as effective as a Salisbury LSD.”  Note that Hissey’s 
preference for disc-type limited slip over cone-type is not universal; it’s apparently a good topic for argument among 
performance buffs. 

Greg Wells of Coventry West says, “The main problem with the Dana as we see it is that it is different and requires 
special Dana-style rear brake rotors.”  Note that the only difference between the rotors used with the Dana and the 
rotors used with the Salisbury are the access holes, so the Dana ones could be used on the Salisbury.  It would therefore 
make sense to stock only the Dana style, but Wells says the ones with holes cost significantly more than the ones 
without holes so they stock both.  Obviously, you could buy the cheaper Salisbury rotors and drill access holes in them 
for use on a Dana. 

“That, plus the fact that it doesn't have a drain plug and people thus change the diff lube even less often compared to the 
Salisbury.  Our rebuilder, Dick Maury, says that the L/S clutch setup in the Danas is not quite as good as a Salisbury in 
his opinion and that the carrier may not be as strong, but he also points out that we have seen Danas in 6.0L TWRs, so 
they obviously can handle the power.”  Apparently, the items that fail on the Dana are “those silly little clutch 
retainers”, whatever that means. 

 

DANA DIFFERENTIAL SERVICE:  When working on a Dana unit, you can get the seals from Jaguar, bearings from 
a local bearing house, and the clutches, shims, and those silly little clutch retainers from any performance shop that has 
access to Dana rear end parts.  When ordering, they will usually ask for a ring gear diameter and an “axle” spline count. 

 

DIFFERENTIAL BREATHER:  John Goodman reports on special parts for the XJR-S:  “Looking through the parts list 
I notice that there is a revised diff cover with additional baffles.  <Quote manual> ..."the diff rear cover is redesigned to 
improve breathing at high road speeds.  The altered baffle plates direct oil flow so that turbulence is kept away from the 
oil breather."” 

 

DIFFERENTIAL OIL CHANGE:  Getting the fill plug out is no picnic.  It has been suggested that removing the center 
reinforcing plate under the final drive unit (14 bolts, 6 with nuts) may be worthwhile.  Don’t worry, the whole car won’t 
fall apart while the plate is out. 

Many Jag owners suggest a length of plastic hose and a squeeze bottle for topping up or filling up the final drive unit.  
The hose should be long enough to feed out the right side wheel well so the oil can flow downhill.