As mentioned in page 1 of the “Mustang IRS project”, the Jaguar rear end has remained mostly unchanged in all the various models of Jaguar from 1960-1987 with the exception of wheelbase width from hub to hub.  Because of this, most of the moving parts from the various years are interchangeable. When attempting to locate a unit, the easiest way to know what you are getting is to look at the model and year the assembly came out of.  The following is a basic list of what a given year and model of Jaguar will have for a rear end assembly, however, this list is just a guideline and probably not all-inclusive.

It is important to note that all the units from the 1969-1987 XJ6-XJ12 are basically the same except the differential axle bearings on the pre-1975 units use ball bearings rather than roller bearing.  These bearings are no longer made and the only way to replace them with the more modern roller bearings is to replace the differential axles with axles from a 1975 or newer assembly.  Fortunately, there is not much strain on these bearings and they can be completely dissembled and inspected.  Assuming no problems are found, they can be reassembled and used for many more years/miles.

Even though IRS rear end assemblies are available in many Jaguar models, the best choices are the 1969-1987 XJ6-XJ12.  The simplest reasons are cost and availability. Depending on the year and model, an XKE is a $20,000- $100,000 car.  With these kind of car prices, it stands to reason that the rear end assembly out of an XKE is probably more valuable to the Jaguar community and, hence, will cost much more than the nearly identical unit out of an XJ6-XJ12, so why mess with an XKE. Not to mention, in populated areas, due to availability, purchasing an entire XJ6-XJ12 parts car may be cheaper than just the IRS assembly from a junkyard.   It is important to note that all the parts in the XJ6-XJ12 units all years up to 1987 are interchangeable, but some of the parts on the early XKE units are not interchangeable with the other models and years. 

Once you have your Jaguar IRS unit, next comes the task of disassembly and cleaning.  When it comes to a task like this, I have five important pieces of advice that aply to all rebuilding projects:

I have a collection of shop manuals and have at least one for every type of vehicle I own. If some part on one of my cars came from a different vehicle, I locate and purchase a shop manual for the make and model of the donor vehicle as well.  I was able to purchase a CD on eBay for under $30.00 that was the full shop manuals for the various Jaguar makes and models in PDF format.  Any time I need to work on a specific section of the IRS assembly I can simply print out the pages I need. Having such a reference tool is important due to torque specification, tolerances, exploded views of assemblies and all the directions it gives in basic rebuilds and repairs.

As you begin to pull things apart you will find parts such as seals or small pieces that are so obviously worn out that you may have the urge to throw them away, DON’T DO IT!  The problem with prematurely discarding things is once you throw something away you no longer have it for a reference. When working on any rebuilding project, I always take things apart and after everything is back together, I then consider throwing out things that are no longer usable.  Having the original worn parts can often times make finding the replacement parts much easier, or in the case of not being able to find a part, having the original part is essential for fabricating a replacement.

As stated before you are rebuilding a used unit.  As parts are used, they often times get certain wear patterns.  That means that if a part comes from a specific place or side of the rear end assembly and is being reused, then it needs to go back where it came from.  Also, knowing the approximate starting location of a part can be a huge help during reassembly. Often times, these types of projects can last weeks or months, which makes remembering part location more challenging.  The easiest way to accommodate marking locations is to mark things as either driver’s side or passenger’s side.  A Sharpie marker and a good punch set can easily aid in this process.

In today’s age of digital cameras, there is no reason (short of not having a digital camera) not to take many pictures during the disassembly process.  These pictures can be used later to ensure that things get reassembled correctly, not to mention they are wonderful to have if you want to create a web page documenting your work. :)  I like to take pictures of the complete assembly, as things come of, and an exploded view once all the parts are off, especially if there are several smaller parts that go together.

The Internet IS an increasable tool for the restoration of cars and trucks all makes and models. Not only is it filled with tech articles just like this one, but it is also a wonderful place, through the many forums and message boards, to meet and exchange info, ideas and experiences with others from all over the world that have done or are in the process of doing similar things. One such Mustang forum “FYI Ford” put me in contact with an individual who had already put a Jaguar unit in his Mustang, another that had done the install in a street rod and their ideas and experiences have been a huge help. Also there is a wonderful Jaguar forum “Jag-Lovers” that is a good place to go if you have questions specific to the Jaguar parts you are working with. Keep in mind that some Jaguar owners are not happy that the IRS assemblies, from their favorite cars, are being used on other makes and models, so it is often times best to tread lightly and not take offense with the occasional poor comment.  If you take the time to understand and except the forum personality than all will be fine.  As a whole they have welcomed me with open arms.  Sometime after these pages launched I found there were lots of people out there interested in IRS so I created an IRS specific forum IRSuspension.com

Breaking down the Jaguar IRS unit into its main pieces: cage, differential, disc brakes, half shafts, Lower Control Arms (LCAs), shocks and hubs, is relatively simple. Start by first making sure all fluids have been drained from the differential, and once this has been done, the unit can be flipped over so that it is sitting on the floor upside down. Now you can remove the bolts that attach the bottom plate to the cage and differential.  Once the plate is off, start at one end and remove nuts, washers and shafts attaching the LCA to the hub, taking care to separate out all the small pieces into bins (this applies to all small pieces further in the process, keeping parts separate and their location notated).  The shaft connecting the LCA to the hub will need to be driven out with a punch or rod. Repeat the process on the other side. NOTE once the shaft has been removed, the hub and half shaft will drop so make sure the hub is supported so that you can set it down rather than letting it fall and risk damaging it.  Next remove the nuts, washers, shaft and spacers attaching the shocks to the LCAs. Once again the shaft will need to be driven out. The only thing left holding the LCA is the nuts, washers and shaft that connect it to the cage and differential, and once said shaft and nuts have been removed, the LCAs can be lifted out.  NOTE between the LCA and the cage is a series of washers, spacers and seals, this is one of those times to either notate or photograph their location, also once the LCAs have been removed be sure to stamp them as DS or PS for drivers side or passengers side.  Such marks will be needed on all further parts that are removed.  DO NOT stamp any of the aluminum or machined surfaces because you can damage them.  To mark such parts simply clean off a small section and use a Sharpie.

Now that the LCAs are out, there is easy access to the four nuts holding the inner half shaft u-joint yokes to the disc brakes and differential axles.  Once these nuts have been removed, the half shafts can be pulled free of the assembly with the hub and set aside for further disassembly later. NOTE between the yoke and the disc brake rotor on each side is a series of shims that are used to adjust camber.  Make sure to remove them from the back of the yoke or from the front of the rotor and save them since they will be needed later.  The only thing left in the cage should be the differential with brake assembly and the four coil over shocks.  In order to remove the differential, you must first disconnect any e-brake bracketry and springs as well as brake hydraulic lines between the cage and differential.  Once these parts are disconnected, the differential and cage can be rolled over into the upright position with the cage on top.  Remove the four bolts that connect the differential to the cage and the cage can be lifted off leaving the differential and brakes as a stand-alone assembly.  Four bolts hold the coil over shocks to the cage and removing them completely empties the cage.

At this point, I set the differential assembly up on a workbench so that I could finish stripping it.  Each caliper is held on with two bolts and, once the calipers are removed, the rotors will slide off of the differential axles.  You can then either remove the five bolts on each side that hold the differential axles to the differential, or you can leave it as an assembly to be dealt with later in the differential rebuild/freshen up.  The only thing left to break down is the half shafts and hubs.  To remove the half shafts from the hub, remove the keeper pin, castle nut and washer from the end of the stub axle.  Now the splined shaft can be pressed out of the hub and ,once they are free, the unit has been broken down to all its key components. NOTE there is a specific thickness spacer between the wheel flange and the splined end of the half shaft.  That spacer is there to set hub bearing preload and may be different from the one in the other hub so I recommend measuring the thickness with a set of calipers and notating it to ensure the spacer is returned to its original location.  After talking to a Jaguar rear end expert, I learned that most of the time, even if you replace the bearings and races, the spacer(s) that come out of any given hub will usually be perfect to correctly set preload during reassembly. Each component is now ready for further breakdown.

The hub has many bearings and seals at both the LCA mounting point and at the wheel flange.  Before removing any of the bearings and seals, I recommend removing the zirk on the bottom of the hub between the two LCA mounting points.  Failure to do so may result in accidentally snapping the zirk off while working on the other parts of the hub. To remove the LCA bearing components from the hub, start by popping out the washer and spacer.  Under that you will find a cloth seal that needs to be pulled out and then the bearing retainer under it needs to pried out or taped out from the other side. Once the retainer has been removed, the bearing and bearing shim will come loose, and  below the bearing is the bearing race retainer and corrisponding race. The last things too be removed are a spacer tubes and shims from the middle of the hub.  Both tubes and all shims will need to be removed before flipping the hub over and repeating the process on the other side.

Exploded vew of the parts that go in the hub