Can a rear end from a 95 Xjs 4.0 bolt in a 90 Xjs 5.3 ? Would it even be worth it to get ob brakes?

 

Yes, the complete IRS from a 95 will bolt into a 90. I'm not sure whether the brake lines or the emergency brake cable are a direct fit.

Outboard brakes definitely have their advantages. I had to pull my IRS to rebuild a seized rear caliper, and opted to rebuild pretty much everything while I was there. I also upgraded to vented rotors. This solves the performance and heat issues associated with the original solid inboard rotor setup.

If you do decide to go to the outboard setup, future service will be easier. You can also go more radical with the brakes if you decide that's what you want. BTW, I'm not sure whether the 95 XJS had a solid or vented outboard rotor.

Here are some pics of my inboard vented rotor conversion:
Dave's Jaguar XJ6 LS1 Swap

 

Yes it's quite an easy swap and worth doing. The inboard brakes are interesting but inferior on a road car. The uJouints are better on the outboard units. The E brake cable will work perfectly with the later IRS. The only issue you might have is the brake hoses. I don't know how the 1990 is but the early XJS have a single fluid channel for the rear pair of calipers with a T fitting bolted to the IRS cage. The outboard brake cars had a more sophisticated ABS system that used a separate channel for the each rear caliper so there is no T fitting. You might have to get some new hoses at the least and swap over the T fitting setup from your old IRS. Its a very manageable problem. The good news is the metric hoses are fairly common so you may find them in stock at your local auto parts store.

Consider that the 90 IRS is going to be a high bias power lock with 2.88 diff ratio. The 1995 IRS is a 3:54 low bias power lock which will make you XJS scoot off the line but rev high on the freeway. If you want to keep the 2.88 you can swap the diff too.

 

I basically agree with what's been said. I'd strongly consider the swap myself if I ever had another XJS.

But, just to play devil's advocate for a minute......

Unless you're a very hard driver and/or pile up tons and tons of miles the future serviceabilty aspect might not be much of an issue. The inboard set-up may serve you perfectly well. With new discs, pads, hoses, and rebuilt calipers (which you'd probably want to do even if you swapped to outboard brakes) you'll be good-to-go for many, many years. At the most you might need new pads....which are not at all hard to replace with inboard brakes. Maybe thirty minutes.

And, unless you're a very aggressive driver the inboard brakes will work perfectly well in terms of heat/performance.

I'm not trying to talk you out of the idea, especially if it's something you really want to do. There are plenty of up-sides to the swap.

But, IMHO, don't feel obligated to do it

Cheers
DD

 

Thank you all for the info. My 90xjs conv has ABS brakes. I purchased the 95 /4.0 xjs for the interior parts for the conv and the low mileage engine/trans for our 97xj6 if I ever needed. I was thinking of the trans change to the 700r for the 90. Im going to pull the rear end before I send it for scrape.

 

The OB rear would be worth a few dollars, so definitely worth removing

 

I am doing the exact same swap on my 90 xjs, my rear end is out of a 94 xjs aj6. One good thing is the speedometer pickup is the same and in the diff which will provide the correct speed to the speedometer. I am going to have to get custom brake hoses to attach to the calipers as the 90s are not long enough. I will have to fabricate a mount for the parking brake as well. The nice thing is the facelift cars all had control arms with the rear anti roll bar mounts so I can easily attach my addco rear sway bar without having buy one of the kits which have a mount included. I plan to do a write up on how I did the rear end swap when I complete it which at my current rate of working on my xjs will be a year from now .

 

My only input it's that there is no such thing as an emergency brake. Don't believe me? Give it a pull in an emergency ;-p My xjs appears to be fitted with a parking brake. ;-p

 

Completely agree, the inboard "parking" brake is pretty useless. On my xj6 I purchased new everything to make it work better. I am hoping the outboard drum style parking brake will be better.

 

Lost my brakes in an old Dodge a long time ago. Shifted the auto stick down to '2' and rode the emergency brake to a full stop.

It won't do it on it's own, but when you lose your primary brakes, the parking brake immediately became an emergency brake.

 

I did this swap on my 1989 XJS coupe. Beyond the obvious advantage and ease of maintenance of going from inboard to outboard brakes, going from 2:88 to 3:54 gears made a phenomenal difference in the car's performance. Some folks told me, "beware, you'll trade off highway mpg for streetable performance". 1) I don't drive the car across country and do most of my driving around town where the 3:54 gears make a noticeable difference. 2) My mpg was minimally impacted and wasn't really a great concern for me anyway. I sourced the IRS from a local Jaguar yard. While it was a little steeper than I wanted to pay, the results of the swap made it all worth it. My shop did the swap and said it was pretty straight forward. The one thing that was noticeable was that the car now had a pronounced rake. It seems that the '95 IRS's springs are stiffer than the original '89 springs, causing the rear of the car to sit higher than it did previously. My shop swapped in the old springs and, viola!, good as new. The XJS now has great streetability, easier maintenance and has a "factory" looking stance. I intend to perform the same sway on my 1989 convertible, after I swap out the V12!