can you post some pix of the rear end??  seeing exactly what you are up against will give us a better idea of where you need to take the parts.

WOW that really is just like the Jaguar unit.  I would think any competent driveline shop should be able to do it especially if you give them the following info of the process I used.

Turn down, cut, press & weld:
  -  Use the yokes from the solid half shafts to make a mechanical tubing type half shaft.  This is done by turning down a section of the half shaft near each yoke end to a size that will be a .002 to .01 press fit in the mechanical tubing that will be used to connect the two ends.   Then cut the yoke ends off of the half shafts, leaving about 1" - 2"  of turned down shaft attached to each yoke.  As mentioned, thick wall mechanical tubing cut to the correct length will join the two yoke ends together by means of a press fit as well as a bead of weld around the base of the yoke and mechanical tubing.  One major advantage to using this technique is by converting to a tubing type shaft, weight is shed and, if repairs are needed in the future, they are simple to do just as you would with any other tubing type drive shaft.  You may wonder how tubing could be strong enough, especially when you consider the original shafts were solid, but the reality is that the modern materials used to make thick wall mechanical tubing are stronger ounce for ounce than the materials used to forge the original shafts and the strength is probably fairly close, if not better, on the modified shafts.  This option is usually less expensive than the one mentioned above because it is easier for a driveline shop to index the yokes and avoid having the half shafts warp.  After discussing the options with several machine shops, as well as others who had narrowed a Jaguar rear end, I decided to have my shafts narrowed via this technique for both cost and reliability.  NOTE the larger the diameter of the mechanical tubing used, the stronger the half shaft, just as an example, a tube 1.75"  O.D. is almost 4 times stronger than tubing of the same wall thickness with only a 1.25"  O.D.  Also, for ideal penetration while still maintaining strength, ¼"  wall tubing will be best for this application.  Several aftermarket companies that narrow up Jaguar rear end assemblies use 1.75"  O.D. and 1.25"  I.D. DOM mechanical tubing.


Red lines show modified yoke ends, blue lines represent mechanical tubing, and green lines represent the welds.

As for the LCAs they look like square tubing so that should be easy to cut and sleeve using another piece of square tubing.  there again a local machine shop should be able to do that.  Let me know if any of this helps or if I can help further.

Last edited by Daze (3/02/2011 4:18 pm)

what year Maserati is that??  If you go two thick on the half shafts you are going to have problems with interference with the shocks.  As far as a place that has "done lots of these"  any shop that specializes in  drive lines  does this kind of work every day.  They may not have done an IRS specific application but they have done lots of similar stuff.  the shop I took my stuff to had never done Jag parts but they new exactly what to do because they had done similar work for other applications.

I think it's from a 1981 Quattroporte.  Rotors are 3/4" vented.  The 4 bolt holes appear to be 2 3/4" center to center.   LCA'a are squared where they bolt up to the center section but the long part is slightly larger than     2 1/2" OD round while the axles are a little bigger than 1 1/4" OD. 

My thought is that some of the Jag pieces would interchange but I'd rather not since the Maserati just seems a little stronger.  I do have a Jag rear end just in case I need to mix and match. 

One other note....hubs are Ford/Mopar 5 x 4.5"

Thanks for the help, Doug

I tried looking for a part number on the rotor but no luck.  I think the part would be hidden while it's all together.  I don't think I want to try taking it apart just yet, but will eventually for you.  Aren't the Jag rotor much thinner?  I seem to remember they were skinny and non vented.    Here are a few shots taken today.  You may be able to see the tags that say PL (posi lock) and 3.54.  I was able to turn it by hand so that was good. 

Last edited by Daze (3/04/2011 7:41 am)

I've seem some Jag units pretty narrow but I need to look up how much is workable.  Thanks for the link.  I'll check it out.  Yes, that other link is my other Hillman.  That one is done although I did just add fuel injection to it.

I do like strange.  A few more can be found at www.dougscars.com.  I need to update it because a few are missing.

Yes, ERA is a good source.  I plan on talking to them.  Might be able to buy shafts from them.

Do you mean the Cobra valve covers?  They have a wide track width compared to what I need.

Very nice.

Ralphy wrote:

Doug you may end up with an unworkable geometry narrowing such a large amont.  Daze could probably answer that better

Hey Ralphy good to see you posting again, it has been a wile.  As to the geometry issues 53.125 is the narrowest Jag ever made it and you, (dlyle) are talking about narrowing it to 48.75 -50.75" which is quite a bit. What we really need is for Joe to punch the numbers in to his cad file to see how much it effects camber. Here is the camber curve of my set up narrowed 2.125" per side compared to a stock XJ6 unit.  As you can see my camber curve is less aggressive so you may be able to remove that much with little issue, but to be sure we would need Joe to run the numbers.

Last edited by Daze (3/04/2011 7:56 pm)

Doug,
It seems to me if you narrowed an IRS all things would be relative. You are narrowing the unit only I would think because you are doing an installation in a narrower (track) car. A narrower (track) car will have more body angle per inch of travel than a wider car. So to me it would seem you need more camber per inch in a (narrow car) shorter distance. The only thing that would change are the ratios from point to point. Your units pivot points create a uneven rectangle . You shorten the two longer sides of the rectangle, (half shaft, wishbone). But the distance  between the wishbone and universal joint stayed the same and that is where the problem is. This may and should be able to be changed and it would be minimal because it's the short sides of that uneven rectangle. On the C3 you only need to move the inner end of the camber rod.

However Daze and others can do the math. Think bigger offset wheels to keep the rear wider. This is not the only board where this issue has been brought up.

Last edited by Ralphy (3/05/2011 8:41 am)

Yes you do take out equal amounts.

Here is the issue, when you are looking at a picture of your irs and you wish to shrink the photo it changes dimensionally horizontal and vertical. That would be ideal! What you would be doing is changing only the horizontal, the length. The distance up and down between the wishbone and the half shaft remains the same and this causes a new geometry.

Hope you understand.

I think I may need to narrow mine down to 48 based on early estimates.  There are several guys on the HAMB forum that have run them at 48 with no problems.  I need to keep researching to make sure there aren't any hidden obstacles that can't be overcome.  One thing I have to check is the with of the center section from rotor to rotor.  Since my rotors are over 3/4" each I think that makes it slightly wider than the Jag unit.  I do have a Jag unit in the garage so I will measure.  Thanks again for the pointers guys.  That's why I'm here...to get educated.

Thats great info to have!!!  Mike at CWI really knew his stuff so if his minimum was 48" I would say that is probably as far as one should go.  I am sure the narrower units work but anything less than 48 is probably not working as well as the wider widths.  That's Just a guess, but every time I talked to Mike at CWI I was very impressed  so I would tend to trust his decision.

"research"???  whats that??  Just kidding I spend as much if not more time doing research and studying things than I do actually working on my car.  It has served me well to go in to a project with as much education as possible.  I would love to see some of those photos you found with the narrower units.  Also I wanted to let you know that when you post a picture address, if you put [img] before the image address and [/img] directly after the image address it will actually post the picture to the forum rather than just the link