I am going to tackle the removal and refurbishment of the rear axle and suspension on my xjs, i will also then be able to get a good look at the chassis when it is removed,
Has anyone got any advise for me about how best to proceed, i intend to completely strip down, shot blast, repaint and replace whatever is required,
Same with the chassis underneath, i am in no hurry so i will be able to do this as
A 2014 project, not sure how to treat the under chassis,
All advise will be most grateful,
Thanks in advance.

 

Take a look at my blog I have a few pics of when I did mine a year or so ago.

I used a trolley jack to get the rear out. Then made a gearbox jack from an old trolley jack to put it back in. I can now have the rear out of the car in under 20min, I do have under the diff exhaust that makes it easier.

Getting the rear out is not too hard. The hardest part is getting handbrake stuff out of the way. There is a bracket on the RHS (RHD car not sure about LHD) that holds the brake linesand is bolted to the subframe mounting bolts. I removed the pipes making it easier to get the bracket out of the way. There is also a speedo drive in the diff cover plate be careful of this, lower the rear enough to remove the sensor, and don't lose the plastic shims these set the clearance for your speedo sensor.

You may as well replace the mounts while you are in there.

I would suggest using POR15 to paint the cage. I powdercoated mine and used POR15 on the front subframe, this stuff is great and far more durable than powdercoat. This stuff goes a LONG way I bought a small tin and have used less than 1/2 of it for the whole front and a few other things. Just brush it on and it drys like a mirror the brush marks just disappear.

 

Consider retrofitting outboard brakes. Jag switch to outboard brakes in 1994 and you can too. It makes the car stop better and pad changes are easier. It's easier to do than it sounds.

POR15 is great stuff using it is a great idea. SEM has a competitive product that's about 1/2 the price and it's the same hard as nails urethane formula.

You can get maintenance free premium U joints from Autozone, they cost a bit more but they dont have zerk fittings, are sealed better and wont throw grease all over as they spin.

Reseal the diff. It's most likely leaking somewhere...the oil finds it's way on to the inboard brakes rendering them less effective.

Rebuild the LSD if it needs it and consider a diff ratio change. Removing the 2.73 for a 3.08 or 3:31 will put some pep in you xjs step. Go 3.54 if you're considering a GM 4 speed conversion. All of this isnt easy to do.

Check the wheel bearings and check the fulcrum bearings. Wheel bearings tend to get noisy and the fulcrum bearings tend to get notchy.

Upgrade the small trailing arm bushing to poly. Leave the large one stock for good isolation.

Replace the exhaust hangers. They tend to loosen up over time.

Consider new springs and shocks. After 24 years those springs are tired.

A properly rebuilt IRS with all new stuff is a marvel.

 

Warrjon, loved reviewing your blog this morning, this is exactly what i want to do this year
I will look into the advise on the paintwork, did you use por15 on the underside of the chassis also are the springs and shocks just a standard size and grade,
A great looking XJS
Mark

 

Icsamerica, i am very interested in your info. The dif ratio change was not something i had considered, i am interested in this, however not actually sure what gearbox/dif my 1990 5.3 auto le mans will have and the effect of changing the dif ratio. Something for me to consider.
Thanks very much for your reply i found it most interesting and will look forward to starting.
Mark

 

I used single pack chassis black under the car over black stone guard. Shocks were replaced with TWR Bilstein all around and 292lb springs on the rear (which are about 45% stiffer). Front springs are stock

The 1990 5.3 will have the 3 speed auto and 2.88 gears. Which is what I had.

I replaced the rear gears with 3.58 and still have the 3 speed auto. The lower diff makes a huge difference in response but it really needs a 4th gear. Does 3000rpm at 100km/h. Heaps of people have replaced the 3 speed with a 700r4, there are kits in the USA for this swap.

 

the 2.88 is not the fastest out of the box, but it gives the best fuel economy , and the most relaxed top speed cruising,

there is nothing wrong with either setup as advised below, but you need to be aware of the different driving styles it induces

i personally kept my 2.88 on my 3 speed GM400

and did a full refurbishment

outboard versus inboard brakes, the only real world difference is the servicing of the brakes, but how often/soon will this need to be done when you rebuild with new parts, i bet it won't get done again for 20 years with leisure driving ?

BB

 

Brake Buster, i agree with you on the inboard brakes the miles i do it would not be worth changing them,
Also with this size petrol engine i think fuel ecconomy is on the top of the list.
Thanks for your reply.
Mark

 

This rear end assembly project is something I think I have to get to, something is a little grumbly and I want to get it sorted, is it possible to check and add diff oil level without dropping all that kit?

 

Going to a 3.54 is one of the best changes. The problem is getting someone that knows what there doing to set up the Jag diff and a lot of shops won't even touch it. Their excuse's are it either whines or clunks after a rebuild/gear change. Another seems to be the electronic speedometer sensor .

 

Just. The fill level plug is at the back of the diff, and you can just get a half inch drive ratchet up there from below to undo it (I think half inch is the size of the plug internal square, could be 3/8). Then use a cable tie as a dipstick. Good plan to change the oil anyway, use Castrol or similar specially for LSD stuff.
Castrol Axle Z Limited Slip 90 Mineral Differential Oil
You can fill the thing with a long tube and a funnel held up on the outside above the diff level, or with a giant syringe and a long tube, such as cattle farmers use for dosing their cattle with medicine!
Greg

 

If you change the fluid make sure you can loosen filler and drain plug before you proceed. It would suck if you empty the fluid and not have any way to refill

 

My 89 has the speedo pickup in the diff. There is a relutor wheel machined into the hemisphere . When I changed my ratio from 2.88 to 3.58 I ended up hybriding the hemisphere with the LSD and gears from the XJ40 mated to the original diff hemi. The XJ40 LSD is not as tight as the XJS, something I did not realise until it was all back in the car.

 

After collecting my XJS convertible from the docks for the first time I had done only about 200 miles when the speedo packed up. I suspected that the previous owner had played around with the mileage and not tightened up the cable. I searched high and low for a cable and eventually realised that there isn't one. So I have an ex California XJS with an electronic speedo.How do I determine whether it is the sender on the diff or the dashboard unit which is at fault ? Any help would be gratefully received.

 

Please list your car year of manufacture, engine, and body type in any posts, or add those details to your signature, so anyone who wants to help knows which car you have.
Greg

 

Hi Greg , I did mention this back in 2014 and you kindly helped me then ! I have still my 1990 convertible V 12 XJS. Work with my single seater has stopped me from sorting out this problem. I did look at the stuff on the lefthand side in the boot. I could find no evidence of loose wires or other obvious problem. I did consider looking at the unit which is apparently on the diffcase.Unfortunately despite putting the car on my four poster ramp, I could not see the item in question. It must be well hidden from below. Is there any access from above ? The commission number if it helps is SAJNW4843LC171302. I need to sort this out as the car is for sale and the French are a suspicious lot and my car has only 33.000 miles on it [quite genuine ] I am the second owner and the couple who owned it from new in California did very little mileage with it. I live in the Vienne 86430. cheers John

 

My memory does not stretch to something I wrote last month, let alone 2014.


Your car will have a speedo pickup in the diff and there will be a shielded wire running from the top third of the rear cover of the diff towards the LHS. Remove the LHS rear wheel and run your hand up the rear of the diff cover and you should feel it. The pickup is held in by a small bolt. See this diagram:

This wire gives a signal to the speedo. Either the pickup or a connector is failing/dirty, etc etc; or the wire between it and the speedo head is broken somewhere. Trace the wire from the diff to a unit (I think this is the case) in the boot LHS front, which I seem to recall is to stabilise the signal to the speedo. Clean all the connectors in this unit and throughout the system.
Test the wire to the instrument pack for continuity, if all OK either the diff signal is not happening or the speedo head is faulty, or there is a break in the pack or its multiplug - which is not the most robust of items. I am not sure what the output signal from the diff pickup is, so I do not know how to test for it, but someone on here does!
Greg

 

Here is a pic of my rear with the sensor circled in red. Mine is not there and the hole is taped, but you can see the bolts.

The signal conditioner is in the boot LHS up inside the buttress above the ABS controller (you will see this mounted to the wheel hump).

As Greg said first place to start is to check all the connectors.

 

Thank you and you too Greg for this information.I have rarely seen a more ridiculous design. It would appear that the first job is to remove the back axle to gain access.Cleaning the area on the diff case properly with the axle in situ before refitting the unit would seem problematic to say the least.Perhaps this is a job best left to a Jaguar main agent.

 

I doubt a main dealer would touch an XJS these days. A specialist yes. In fact, the sensor is the least likely thing in the system to have failed, so will worth your doing the other things people have mentioned. I am nowhere near you, so cannot help directly.
Greg