XJ6 IRS Measurement.
 

I was wonder if there was a list of dimensions for the XKE, early S Type and XJ6 IRS that gives the upper mounting point dimension between the shock/spring bolts?

All my IRS's that I own, they are all out of the cage and I don't have any dimensions for any of the aforementioned models.

Can anybody please help me out or direct me to a chart/link etc...

Many thanks,

Russ.

you might contact member TilleyJon in the MK-2 / S type forum. Most likely he has the info. you need.

Great and thanks for the lead.

Russ.

I just reinstalled the rear end into my S-type. About a month ago. Ill go out and try to measure it once it warms up above "Don't go out there!" degrees. Could be a couple of days.....

Hi Russ,
I got out to the garage and made that measurement. I was able to go straight across between the upper shock bolt heads at the back side of the cage (unusual that there should be so much space!). I got 27 3/4 inches center to center. This is on my 66 S-type, but "As I Understand It" there were 3 different lengths of axle shafts between the E, the S, and at least the MK10 so I have to assume that the cages would probably be different too in order to maintain the shocks' angles. This is not presented as fact (other than my measurement), but merely an understanding which I Believe to be correct. Good luck.

Well Jerry, you are a gentleman indeed.
I appreciate that it is winter in your neck of the woods so going out to the garage may be limited some days.
I thankyou very much for that measurement.
That sounds pretty good as my buddy is suggesting the E Type is about 24 inches which is about what could be expected then compared to an S Type.
My buddies 24 inches is only an estimate and not an accurate dimension.

Here is hoping there are a few more gents out there like you who will be able to fill in the XJ6 and E Type soon.

Many thanks,

Russ.

Hi, just measured the replacement rear end I pulled at a junkyard for my XJ6 series 3. The shock to shock mounting bolt distance is 29 3/4 " ( center to center ). Let me know if you need more info.

Cheers,
Brian

Thanks again to Brian and Jerry for their assistance.
If anybody has a similar measurement for the E Type IRS I would appreciate it also.

In the meantime, is there any where I can look to learn what diff ratios were available in the line of IRS diff centers from E Type thru to XJ6 and what centers might be interchangeable from other models into that early housing???

Probably a simple question to the true believers, but for me I'd have no idea at all.

Waiting in anticipation.

Thanks,

Russ.

Lot of good info on this site:
https://dazecars.com/dazed/JaguarIRS1.html
It's geared towards Mustangs, but does have thorough information on the differences between the years, and a lot of good rebuild info.
I have the parts and service manuals scanned on my site (for the Series 3 XJ6, though most of the parts are interchangeable throughout the IRS run)...
IRS - Rear Suspension
Cheers
David
shop.EverydayXJ.com

Thanks David, I will keep you in mind regarding parts in the future.
I am a hot rod orientated person and keen on utilising the Jag IRS system in at least one project.
I am just fortunate to own one IRS unit from an E Type, an S Type and an XJ6.
Still trying to get my head around the technical stuff and various diff ratios that are out there...
I am looking at using what I know it as the XJ40 hubs with outer mounted disc and park brake setup attached to the early inner section of the old IRS's.
I makes for a much easier exhaust path on confined hot rod builds...

Russ..
US and Other Market cars vary greatly as to what was available in gearing ratios and such...
For the US, The early cars (Etype, Stype, 420 etc) were all posi (power loc) as far as I can tell... The XJ12s and XJS were always posi ... The XJ6 was always open (not posi)... US cars were also mostly automatics, so they didn't have the super low ratios... Most common gearing on US cars were 3:54, 3:31, 3:07, and 2:88. The Etype was the narrowest... XJ and XJS was the widest, and have to be narrowed for a lot of hotrod applications..
Euro and Canadian markets could have some gearing differences... Seems like manual cars went as low as 4:27 or 4:07... Maybe even lower.. And there are some differences as to what was offered as a Posi... I think I have some good articles as to what the differences in some of those markets, if I can find it...
As far as the XJ40 and X300 differentials and rear ends... I don't think a Jaguar application would be as easy as swapping differentials.. whereas a hotrod application may be more doable... There are quite a few differences in the mountings in the cages that I think would take some reengineering to work around.
As far as the Series 3 / XJ40 hub swap.. the stub axle on the XJ40 is quite a bit smaller than the Series 3.... So a swap of those hubs would also need a stub axle swap... There may be some confusion of the late (92-96) XJS hub that would be an easier swap, if it could be found..
There is a really good IRS/IFS group on Facebook that has really taught me a lot about what the hotrod guys are doing.. Simply some amazing engineering going into their projects....
Cheers
David
shop.EverydayXJ.com

Thankyou David, that is very helpful and interesting information that you share.
I have been considering using those later hubs with out board disc brakes...

This is my Jag IRS in a hot rod. It has been narrowed about 2.5" using the method outlined in the Dazecars website mentioned by David Boger in a previous post. The half-shafts were made with drive-shaft tube and off the shelf Spicer parts. The differential is a 3.54 ratio with Posi loc and it is from a late XJS, but the rest of the IRS is from a XJ6. The IRS was used to give the truck a lower ride height/center of gravity and very plush and supple ride (like my XJ6) without any modifications to the body/bed of the truck (which is required for a live axle configuration)

David- if you read this, I'd be very interested in a link to the Facebook site you'd mentioned.

https://cimg0.ibsrv.net/gimg/www.jag...15df2eec4d.jpg
Narrowed Jag IRS in a '49 GMC half ton truck
https://cimg2.ibsrv.net/gimg/www.jag...2fcc2915fb.jpg
Shorter half-shafts fabricated from off the shelf Spicer components. Jag shims were used to achieve the correct camber of the new shortened assembly
https://cimg3.ibsrv.net/gimg/www.jag...38e9e31a04.jpg
Center section is a 'drop out' ladder structure isolated with urethane bushings. I tried using the Jaguar sheet metal cage but would have needed to cut the frame in the truck to fit it so I fabricated this.
https://cimg4.ibsrv.net/gimg/www.jag...5b7697cef5.jpg
The drop-out can't resist the torque to the tires, so locating link is fitted between the chassis and the bottom of the differential to positively locate the diff. There's no movement so rod ends aren't necessary, but convenient to precisely set the pinion angle
https://cimg6.ibsrv.net/gimg/www.jag...a9ad4268a1.jpg
The locating links installed. Parking brake is actuated with a cable to a linear actuator. KYB shocks from a Toyota truck. Brakes are actuated with a Corvette master cylinder with a bore diameter that's the same as the Jag's, An adjustable proportioning valve is fitted to keep from locking up the rear brakes in a panic stop.
https://cimg7.ibsrv.net/gimg/www.jag...f12798bd32.jpg
This IRS uses air bags for springs. They're located on a trailing arm that connects the outer bearing carriers to the chassis. The forward mount of the trailing arm is aligned to the inner pivot of the LCA. Note that the outer hub bearing carrier has been trimmed back about .5" at the top to avoid hitting the frame rail at full upward travel. The upper bump stop is integral to the airbag and keeps the half shaft about .5" away from the frame rail in the event of an airbag/air failure. This truck will probably never carry anything in the bed heavier than a beer cooler and some lawn chairs.

Here is the group I've been following for a while...
https://www.facebook.com/groups/1715863315308125/
Lots of guys on there with early Ford pickups..
Always interesting to see the engineering behind those projects... Looks like your setup is going to be awesome...

Cheers
David
shop.EverydayXJ.com

There's a social forum over on the HAMB for Jag suspensions in hot rods too

https://www.jalopyjournal.com/forum/...wap-group.726/

That is a nice slender mounted IRS you have created there, well done.
The HAMB Jag social group has no activity sadly.

Can you add any more pic's showing where and how those front bars are connected to your chassis please.
Your IRS width must be close to S Type Jag then if you have cut 2+" off and XJ6 diff.

https://cimg3.ibsrv.net/gimg/www.jag...d2af2b937f.jpg
Here's a photo while the truck was under construction. The silver painted arms locate the diff and are stationary. The other arms are pinned to the outer part of the lower control arms and rotate with the suspension movement. Their forward mounting point is on the same axis as the fulcrum of the lower control arm. The air bag (or air spring) is mounted on this arm in such a way as to not impart any torque to the lower control arm.

That is great and thanks for sharing.
Keep up the good work.

What OD round tube did you chose and what wall thickness is it???

I have kin in Chandler AZ, so maybe one day when we are visiting, I could get to see you and your truck finished and in the flesh so to speak.
Best wishes,

Russ.

Russ-

Jaguar enthusiasts and/or hot rodders are always welcome. Let me know when you're coming for a visit. I live in Phoenix and Chandler is just a stone's throw east of us. If you'd like to see the goings-on in my shed for Jag suspensioned hot rod, there's a build blog at 49 GMC Five Window - The 1947 - Present Chevrolet & GMC Truck Message Board Network

The rod end tubes are 1" dia., .125 wall chromoly tube. DOM would have worked just as well, but these were surplus from another project

The moving trailing arms are 1.5" dia DOM with a .125 wall. As I said, all this truck will ever haul is a beer cooler and lawn chairs, but if it had serious HP (has an aluminum 5.3L V8) and wanted to haul anything, the tube should be a truss with more strength.

From what I've read, hot rods in Australia receive quite a bit more engineering scrutiny before being allowed on the roads there. I recall having seen an engineering report on repurposing the Jag IRS from Australia. It had many 'best practices' I incorporated into my installation and was quite helpful. If you've not read the report already, it'd be worth searching for it.

Great build blog and thanks for all the helpful comments.
I look forward to meeting you in the distant future, probably not due for a AZ visit for another 12+ months at best.

Russ.