Its been a while since I've had the car back from the garage, having had a lengthy and exhaustive IRS overhaul and upgrade. Initial inspection of my car after purchase late last year threw up a few issues that needed to be rectified including replacing rear brake pipes and a leaking diff seal, this meant I needed to take out the IRS so I seized on the opportunity to overhaul it. Do it once, do it well and it'll last another 20 years. Except, it wasn't quite that simple, as I started to list the things I wanted on the car it became obvious that this was the perfect time to actually upgrade various other bits as well. So what started out as a simple refurb turned into something far more complex.

Once i'd finalised the specs I set about sourcing the items I wanted. First off I wanted to put outboard brakes on her for future servicing simplicity, so a late model IRS was found and shipped to the garage. Next, having identified several Aston Martin parts that have been upgraded over the Jag, I tracked down some of the strengthened wishbones from a DB7 Vantage. Lastly, I wanted big brakes on the rear so after advice from other forum members purchased some XJR rear hubs, shafts and calipers to bolt on the back. Whilst talking about spec it was important to me to maintain the ride of the car whilst enabling the handling, so a Harvey Bailey ARB was purchased along with their anti tramp kit. Also new shocks and springs from Rob Beere.

Work started in stripping down the late model IRS, and XJR rear corners, pic below shows some of the parts (including the Aston Wishbones) after cleaning and etch coat.



Likewise the hubs were cleaned, but wouldn't polish up particularly well so these were painted silver and lacquered.



The late model rear cage was in ok shape, but whilst out the guys at the garage suggested adding some additional metal to the cage to protect from splitting, excuse the drawing, but all areas encircled with red were reinforced with further steal.



A few more photos of the refurb..





Next - out with the old IRS...





Next the build up of the new IRS begins.. shocks, diff etc all on and back on the car








All re-assembled and back on the car. In these pics you can see in silver the anti tramp kit and new roll bar. We had some issues fitting the anti tramp kit, its sold as correct for all XJS' but we found that it was too long to fit, HB weren't particularly helpful on this front so we cut and welded back at the correct length.





This is very much the shortened version as issues were identified most of the way through but the guys at Alders classics did a great job as usual. She's now run some 1500 miles since in the last couple of weeks through France where she's been superb. The only issue from the upgrade seems at the present to be a knocking exhaust, and a anti lock brake sensor problem to resolve. Otherwise the handling is now superb, the braking as you'd expect is pretty awesome (and surprisingly balanced) so together with the manual conversion she feels like a properly good GT car. Next there's some non related issues to resolve, then next year - the front suspension overhaul.

 

For astons wishbones you will need shaft with eccentric cam to adjust the toe rear wheels

 

Beavis,

Tks for the write-up, really good pics! A couple of questions, if you don't mind. You mentioned that you used XJR hubs. Did you mean from the X08 XJR. The reason that I ask is that the hubs on X308s are the same for S/C and N/A cars, whereas the hub carriers are different on XJRs, but those carriers in the pics are from a standard X300 or X308. So I was a bit confused by your description.

Also, could you tell me the make and model (and price) of those adjustable height shocks? They look a nice bit of kit.

Cheers

Paul

 

Hi Paul,

The rear hubs and carriers definitely came from a 97 XJR (X308), purchased from a member on here.

This is the link to the shocks... Rob Beere-Suspension
They are £155 each and the springs on top. I'm just in the throws of talking directly to AVO to find out the part numbers, as I have to admit to feeling a little 'done' buying them from RB's....

Rich

 

Hi Rich,

Tks for that. I was just going by the part number in the pic. Jaguar state the standard carrier is MJA3290AA (your pic) & the XJR is MXD3290AA. Perhaps very early XJR just used the standard x300 / x308 parts?

Either way, it's good to know they are interchangeable with late outboard XJS which uses a slightly different number. I wonder if they are more robust?

In the UK, Rob Beere has a pretty good reputation certainly for V12 engine builds so let's hope you have paid a reasonable price for the shocks. Would be interested to hear how you get on with rebound adjustment. I use the Gaz equivalent and really like them.

Paul

 

Paul
Are your gaz shockers separately adjustable for each of bump and rebound, or the standard Gaz adjustable ones like I have that, while being adjustable, have a fixed ratio between bump and rebound?
Greg

 

Beavis:


Nice setup you are running there. What did you put in regarding the manual box? Ratios? And did you simply rebuild the diff or replace it? Ratio?


I run a 5 speed Tremec with a 3.27 first gear, wide ratio box. Have changed the diff to 3.54, which is why I am asking the questions.


I have given more than passing thought to fitting the hubs you have, if only to make the brake work a bit easier and to give those diff seals a breather.


-M

 

XJ40 hubs will fit the XJS LCA's you will have to modify the outer fulcrum as the XJ40 hub has a smaller diameter shaft, so bushing the LCA should work. The XJ40 rear end also has spacers in place of the IB disk. They also have toe adjustment.

I have a set in the shed somewhere I bought the rear end for the 3.58 gear set.

I also seam welded the cage prior to powder coating.

 

Great write up, and nice looking

 

The manual box is a standard Gertrag out of the 3.6, and its combined with the 2.88 Diff. Sorry, don't know what that means in terms of gearing, but cruising in 5th on the motorway the engines at just under 2000 rpm at 70...

It was the quickest and cheapest way to convert it, but if in the future the box packs in I may look at something different.

 

Beavis:


Thanks for that. The info I have on the G5 used in the XJS behind the 6 cylinder engines is that it used the following gearing below, which, taken against your 2.88 is not very bad at all. It is very much like what I would have in my car (3.27 first), had I used a 3.31 diff instead of a 3.54. I have the same deep OD 5th, and with the 3.54, the results are quite acceptable. The 3.54 diff matches better, I think, to a close ratio box with something like a 3.0 first gear. I will be eventually changing my box for a 6 speed with a first gear very close to that. A manual box on the V12 XJS is transformative, and I'll bet your car is quite a bit of fun to drive, now!


3.552.041.410.76

 

I like the anti tramp setup, and your whole IRS setup,great job, but didn't see it in the HB site catalog . Whats its purpose, controlling wheel hop? The 4 rubber cage mounts seem to be the weakest point on the already weak IRS, it does not like "dumping the clutch" or god forbid a "power shift". On the trans side, traveling 60mph in 5th gear on level road RPM is reading 1,800, 70mph is 2K. Gears are 2.87 first, 0.82 5th, with a 3.54 diff.
Lawrence

 

Lawrence:


Sound's like you are running the close ratio Tremec 5 speed behind that 3.54. That's a great combination, in line with my own goal of getting to a 6 speed CR box with a nominally 3.0 first gear.


That HB bracket setup is designed to restrain the fore and aft rocking motion of the cage under hard acceleration. You are very right, the four cage mounts are not much, and for what it's worth, neither are the two big end radius arm bushes (had to replace cage mounts once, radius bushes twice- they take a beating when running a manual box in sporting use (non-drag)).


I am doing something similar on my car right now. Using the ladder brace from an XJSC, and placing bushings between the tie plate and that ladder brace. Should provide a similar cage motion restraint.


If I had my way, I'd get rid of those radius/trailing arms altogether. Never been a fan of the rear wheel steering these do under cornering at high speed. If the bushings are not up to snuff (and the mounts) you will experience the color drain from your face due to this steering effect as you exit the turn. Not fun.


-M

 

Greg,

The Gaz ones that I have use a single compound adjustment. Sound like the same as yours but with adjustable platform height. This seems the same as the AVO ones that Rich has fitted. AVO also do a unit withe separate bump and rebound , but not cheap!

Paul

 

Beavis,
Loved the write up with photos.

Thanks.

Did you get the chance to drive your XJS before and after your modification to comment on the degree and nature of the change to ride and handling ?

 

I enjoyed your write up. You will ha e to let us know how the Harvey Bailey anti tramp kits works for you.

 

Hi Paul,

Yeah I did a few miles in her before the installation. Unfortunately though, a whole lot of work was done at the sametime. The IRS got overhauled (new bushes, bearings, shocks\springs, brakes etc) as well as the antiroll bar and the anti tramp, so identifying the specific component that makes the difference is nigh on impossible. The overall handling is now superb, she sticks to the road really well and the new shocks so far also seem very good. I'm no racing driver but there is a definitive difference to the tightness of her rear end (so to speak), which I think is from the anti tramp (ie not rotation from the top of the cage), particularly on quick take offs. I think most importantly for me, the whole feel of the car has changed, and that gives you confidence in the twisty stuff....

 

Thanks Paul. I asked because I have always wondered if having the two separately adjustable was worth the huge extra expense. Do you have any knowledge of the difference, experience of others?
Greg

 

Mike
Yes I did go with the Tremec TKO 600 5sp. I started with using the 3.54 diff with the TH400, still wanted a manual!!!! My goal was to duplicate the gearing "feel" of the Muncie M21/22 close ratio 4sp with 4.11 diff plus having an overdrive gear. I ruled out the 6sp because of tunnel alterations & I didn't need two OD's. I decided on the TKO 600 after seeing the abuse it can take ie: BB Chevy, Mopar, etc.
On the IRS I went with Poly radius arm bushing's & a 1/4" aluminum tie plate and 3/4" sway bar. Other IRS mod's are always a thought.
Lawrence

 

Lawrence:


Yeah, the 6 sp approach with the T56 is hopeless for many reasons on this car. The double overdrive is the beginning.


The 6 speed I am going to do is the Richmond, which, today I discovered, is NLA! That is really too bad, because that is the only box where you can dial in the ratios you want to run.


Everything else forces other compromises that aren't all that pretty.


You've gone the best way for 5 speeds, though. The wide ratio box I have is more suited to 3.31 gearing, for which I had a diff loaded with this while doing the IRS rebuild 2 yrs ago. But, I needed the speedo pickup on the diff, and a 3.54 came along at the time I had the cage apart, and that went in instead. all of which meant that the problem got pushed to the box again. That is OK, because while I like the Tremec, I really want 5 gears that are not OD, and I want the benefits a close ratio set offers.


Hanging in for the Richmond 6....we shall see...


The alternative for 5 speed guys, who don't change their 2.88 diff, is the Geforce. Here, you can again dial in the gears, and a mid 3's first is possible, making that 2.88 workable.


-M