When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
So Ive decided to start trying to understand the rear suspension in 94 xj40, before I throw parts, time and blood at it. What would be the best set of Bilsteins to install in the rear since Ive noticed that it beginning to make noise. I was told by a Jag mechanic over the phone that the top bushings rest on a plate that is most likely worn or broken since its making noise. He pretty much confused the heck outta me. Can someone help me understand this set up? What Shocks are best for my application? Anyway to eliminate unnecessary parts and simplify an arrangement of bushings? Im wanting my car to track well through the network of canyons that I constantly travel during the week. And I want a setup that will last longer than some of the crappy bushings I have seen online. Thanks in advance!!!
You can fit X300 style rears that use a different bushing setup than what you have at present.
I went this route and also added a one piece strut from an X308 but that's a different topic ..here's the thread on my changeover to the upgraded shock system
Thanks Larry! Now Im wondering if I can upgrade to an XJR set of shocks. Possible? Im pricing them out and it seems like theyre the same setup as yours. I do like the difference in bushings and the larger plates. But now Im confused in regards to a caption stating that theyre for cars with comfort suspension. Its darn confusing since I thought an XJR s sporty so why sport vs comfort suspension? Is there something different or special about sport suspension on an x300 XJR? Please help me out... i want a sporty suspension on my car and will go the X300 route. Im ready to buy but not sure what to get... 🙏
Yes the X300 XJR is a bit different back there, not checked springs but I assume they would be different from a VDP - the shocks would be a different grade (sports) but the same physical configuration, so you could fit those and there would be no problem swapping out the springs if you felt you'd want to go with the XJR setup.
The main difference AFAIK is the addition of the rear anti-roll bar and one piece strut - you could fit the strut (as I did) but in order to go with the rear roll bar you'd have to get a different bracket at the rear of the diff.
There's no place to bolt up to on the VDP - plus the cast wishbones on the VDP don't have anywhere to attach the bar either, the area is there but blanked off so you'd have to either replace the wishbones or go with some creative drilling and bushing ...so "some assembly required" to turn your VDP into a "stealth" XJR.
The front rollbar on an XJR is thicker too plus the front shocks would also be a different grade ...etc etc..
To be honest, my VDP is no slouch through the twisties and adding the monostrut might be enough, but each to their own I guess!
I may have not not expressed my plans properly. I dont plan on going the full XJR route. I only meant the shocks. Im looking at the shocks that you accidentally received so Ill be inching closer to getting this done soon👍
I've rebuilt the suspension on both our '88 and '93 XJ40s, replacing the shocks and all the bushings, and from your description of what you want the car to do, replacing the rear shocks and shock bushings will probably help, though possibly not as much as you'd like.
The first time I replaced the shocks on our '93 I used Bilsteins but found them too harsh for my taste (and I love a curvy road as much as anyone). I switched to the OE Boges and really love their combination of controlled but smooth ride. When it came time to replace the rears again, I found a great deal on a pair of Sachs shocks and they behave just as well as the Boges (Sachs and Boge are both now owned by ZF). Noise at the upper corners of the rear seat is usually a sign of failure of the shock upper bushings. As Larry mentioned, your '94 may have the earlier design with "top hat" bushings or the later X300 design without. The large foam spring isolator bushings or "donuts" compress and harden, resulting in loss of ride height and suspension compliance. Here are links to photos:
Rear Shock Absorbers/Dampers Replacement Part 1 of 2 Rear Shock Absorbers/Dampers Replacement Part 2 of 2
A possibly more important consideration is that when the large rear subframe or "A-frame" bushings deteriorate, they cause a significant loss of steering precision by allowing lateral movement of the independent rear suspension (IRS). So I would recommend that you replace those while you're at it. In fact, they will probably make more of a difference in handling and steering precision than whatever shocks you choose. I don't have a photo album dedicated to the subframe bushes, but here are links to some other suspension work:
Polyurethane versions of some or all of the suspension bushings may be available, but I would caution against using poly or hard black rubber bushings on the tops of the front shocks. The OE yellow foam bushes only last several years, but they provide just the right feel and comfort compared to bushings made of harder, longer-lasting materials that I found much too harsh in our '88. Here are some pix:
If your front suspension bushes are in good order, you might want to consider adding stiffening bushes to the steering rack. These were part of a kit fitted to the XJR and XJR-S and they made a noticeable difference on our '93. It's cheap to make yourself a pair:
Another thought is that it would be a good idea to check your wheel bearings, especially the fronts, which require more frequent attention than in most cars, and the ball joints and tie rod ends (inner and outer). Any play affects steering and handling.
Also important is your tire selection. The XJ40 suspension was tuned for tires with a V speed rating (149 mph), which tend to have stiffer sidewalls than tires with lower speed ratings. I once got a good deal on tires with an H rating and could easily feel more tire roll while cornering and less steering precision overall. On the next set I went back to V/Y/W/Z class tires.
And tire pressure makes a big difference. On our '93 XJ40 with 16-inch X300 wheels, I run 33 psi front and 36 psi rear and feel that it represents the best compromise between ride comfort and precise handling. If you have stock 15 inch wheels you'll have to experiment to find the right balance based on the tire pressure range recommended in the Owner's Manual.
The XJ40 steering will never feel like a BMW, but with the right tires and healthy bushings the handling is excellent for a 4,000 pound car and will have no trouble keeping up with a contemporaneous 7-Series. To make improvements much beyond the factory design would probably require more than firmer shocks, and just using XJR shocks without the other revisions would likely not result in a well-tuned setup. To get the full benefit you'd want to add the monostrut and anti-roll bar setup that Larry mentioned.
Thank you! Great stuff to read. Now I know where Im going with this. I have a set of W rated 16" tires that I want to mount but won't do it til I at least replace the rear suspension bits. Well worth to the carrier mounts too. Lots to keep thinking about and Im starting to understand the suspension on these cars a bit more. I currently have gas konis and theyre not bad but I do prefer Bilsteins. Thanks Larry and Don!
By the way... according to my VIN the the suspension is of the earlier type... i really gotta get under there and confirm what I really have but do you think that the X300 Bilsteins work still or is that a nay no?
By the way... according to my VIN the the suspension is of the earlier type... i really gotta get under there and confirm what I really have but do you think that the X300 Bilsteins work still or is that a nay no?
I would recommend examining your suspension before you order any parts. Larry may know if the X300 shocks will work in the XJ40 suspension, but the part numbers for the upper mounting plates and upper spring pans are different between the two models, and off the top of my head I think the lower mounting points may be different. Note also that the XJ40 setup uses the "top hat" bushings to isolate the shock shaft from the upper mounting plate, but the X300 does away with the top hats and uses a larger lower foam isolator bush.
At the time I tried the XJ40 version of the Bilsteins they were firmer than the OE Boges. You may like them.
Take a look at the wishbones - if they are pressed steel you have the earlier type but if they are cast, you have the 94MY type. The internal diameter of the lower shock bush and bolt is different in both arrangements so shocks are also different; bush is not replaceable on later type AFAIK.
If your springs rest on a collar/plate on the shock absorber = early type ..on the cast wishbone = later X300 type.
Why not put your VIN in the signature line then we'd be able to give you better guidance. Just stating the model year of first registration doesn't necessarily mean a 94 is a 94, it could be a 93 etc.
Primary differences between a 93 and a 94 is the refrigerant type and rear suspension. 94's have factory R134A systems while 93's will have R12 or converted R134A A/C systems. <edit: R134A WAS fitted to 93MY cars from VIN#667829
I believe I have Factory r134 and here's a pic of the suspension. You tell me because they look casted but I may be wrong. Can you tell? Im familiar with pressed steel and casted parts for other cars but Im just not sure on the Jag. Thanks!
Larry may correct me, but that looks like the XJ40 wishbone, as illustrated here. It's stamped in two halves and welded together along the side seams visible both in the illustration and in your photo. Another telltale sign is the hole for the lower shock bolt near the hub yoke:
The X300 wishbone has a more rounded cross-section, and you can see the obvious "socket" or spring seat where the lower end of the shock fits through (next to the hub yoke):
BTW, Larry, I know our '88 was R12 because I converted it to R134a, but I thought our '93 was R134a from the factory. Do you know if when a dealer did the conversion the entire hoses were replaced, or were adapters fitted to the ports?
Looks like I'm off on the R134A/R12 thing - I guess R134A was introduced from VIN 667829 and that probably includes the 93MY, correct?
That wishbone is definitely not a cast X300 type, so I'd guess the later shocks/spring setup wouldn't fit after all - the shocks for this type of suspension have the lower spring seat attached to the shock body as the spring sits on the shock rather than on the wishbone like the late 94's and X300's.
Guessing the OP's car is probably a 93MY then?
Larry
Off the top of my head the VIN for our '93 is 675***, so maybe R134a was factory from the beginning of the '93 MY?
I think that must be it, Don.
Of course I forgot to mention the other BIG difference between the 93 and 94 models ..
The elimination of the glove box and the addition of the passenger side airbag in its place. Much as I adore my 94 I sure wish it still had a glove box!!!
Thanks fellas! That settles it. I have the older suspension which is not that bad but i was hoping it was the later stuff. Yup mine has no glovebox. I dont care since my other doesn't have one either 🙄. Im not Joe Pesci so I dont need a place for a firearm or paperwork. 😂 Now its time to get things back to spec!
I find it very odd that your car has the earlier XJ40 suspension and no glovebox! Maybe the SRS airbag was also introduced in 93MY?? (although I thought Don's 93 has a glovebox?)
Oh and another difference I remembered - 13 screws hold down the cam cover on a 94 - also oil filler cap is mounted on the cam cover.
With that VIN, (according to the parts catalog) you should have the later suspension UNLESS a previous owner replaced the whole rear suspension due to an accident or whatever at some time ..they do interchange, so anything is possible!
Not to worry, both systems perform well if components are in good shape!
To get the full benefit you'd want to add the monostrut and anti-roll bar setup that Larry mentioned
In my experience and observation over the years it's anti-roll bars that make the biggest improvements. Larger bars, and/or adding a rear bar, has a very dramatic effect.
Of course *many* things enter into the overall picture but if we look at manufacturers who have offered 'standard' and 'sports' suspensions I think we'll see that anti-roll bars are the biggest players.
I like A) soft-ish/standard springs, B) high quality, performance-oriented shocks and C) upgraded/added anti-roll bars. That formula has always given me the improvement I was looking for on any car I've owned. Always worked well in real world driving.
02-21-2017, 11:03 PM
Rebuilding my suspension to handle Canyon driving
