I recently acquired a low mileage (35,000) 1990 XJ40 (Sovereign) which has a handling issue that befuddles me. Having driven other XJs (I also have a Series 2 and XJS), I know this isn’t normal but my initial attempts at diagnosing have proven fruitless. Maybe someone on this forum can offer their opinion or suggestions.

I purchased the car sight unseen and flew to its location, followed by an interesting drive home (another story for another time). The car still has its self leveling rear suspension in place and it seems to operate correctly. Upon first driving the car, I thought it suffered from the common steering rack bushing failure that I have experienced in my other cars. Only later did I learn that the XJ40 steering rack uses a different bushing from earlier cars. Also on that trip, the driveshaft developed a vibration after driving about 1000 miles. Had to keep the speed at no more than 60 mph and we eventually made it home.

The initial handling symptoms were that the car seemed to wander. Upon hitting the brakes briskly, the car would dive to one side or the other. Diving to one side or the other seemed more related to the condition of the highway pavement and slope and not because the brake calipers were hanging up. When gradually braking, the car tracked straight. The steering seemed fairly tight and it felt as though either one or another suspension component was loose or possibly the suspension subframes were loose. Upon getting home, I realized that the steering rack bushings could not be replaced as in earlier cars but did install a shim kit fitting between the rack housing and the subframe mounting points. This did not change the overall behavior. I then examined and replaced the front fulcrum bushings (lower & forward most bushings on the control arms) as they had some small cracks. While the subframe was out for those bushings, I preemptively replaced the front subframe rear bushings and the vee mounts. Front wheel bearings were checked for play and the right side adjusted slightly. Rear wheel bearings haven’t been checked for play but the symptoms don’t seem to fit a wheel bearing issue. The above was in response to the wondering and diving to one side or the other.

While doing all this, I also addressed the driveline vibration and removed the driveshaft and replaced the Jurid, the center support bearing, and rubber components in the transmission mount. The alignment of the driveshaft was done by means of moving the center support bearing to achieve the smallest amount of vibration at all speeds and conditions. Crude but eventually effective.

The result of the above was that on smooth pavement at a steady speed, the car tracks evenly and smoothly though it clearly needs new shocks. There is no driveshaft vibration initially. But after a period of driving 10 or so miles, and after varying speed and road conditions, a vibration may or may not develop. Hitting the brakes at anything more than a gentle slowing will cause the car to dive significantly to one side or the other. It very much feels as though a suspension or subframe bushing is VERY worn. Once the vibration develops, it typically stays at a variety of speeds including at low speeds around town. It almost feels as though after driving for a few miles, road irregularities and/or speed changes are causing something to misalign which then causes the suspension to misbehave and the misalignment also causes the drivetrain to be out of alignment which creates a driveshaft vibration.

Are there any specific bushings that might cause such significant issues? Again, this is not a subtle drifting to one side or the other but significant. Might the SLS be malfunctioning in a manner which causes this erratic behavior? Could a binding brake caliper possibly cause such extreme issues? Not being familiar with this model and its usual failings (other than what I’ve read on line), are there typical areas that should be addressed before all others? Rather than just dive into a complete renewal of all suspension components (after all, the car only 35,000 miles), I’d like to first concentrate on suspect areas. So far, all my efforts have only taken care of the over 60 mph vibration and the handling problem is still the same. All opinions are welcome.

Your thoughts?

 

How are the tires and have you taken the wheels off and put then back on again? Do you have a warped wheel?

Larry

 

Second set of wheels / tires on the car. 16" Blizzaks on good condition XJS wheels that had previously been on my BMW (tires of course, not the wheels), both known to be good.

 

Hi Tony,

This obviously isn't your first rodeo, so kudos on your work thus far.

My first suspicion when I began reading your account was that the front subframe rear pivot bushings had perished, which allows the entire front subframe and steering rack to wander and tramline and to rotate right or left under braking. But you have replaced those bushings. When you replaced them, did you pay attention to the orientation so the new bushings were installed with their central spokes oriented at the same clocking as the original bushings? If the bushings were installed at, say, 90 degrees off of proper indexing, the open spaces in the bushings would not provide the necessary support against movement the solid spokes are supposed to resist.

Another possibility is that your rear subframe A-frame bushings have perished, allowing the rear subframe to pivot right or left, which has a surprising effect on steering (it essentially allows the rear end to steer the car). A quick check is to inspect the bushings from the side of the car to confirm that there is some space between the subframe and the body of the car. If the body is resting on the subframe ends, the bushings have perished. Another clue is if you hear differential gear noise in the passenger compartment while driving.

Regarding the vibration, I can't explain why it may not appear until after you've driven awhile. I don't know where you sourced your parts, but I once had problems with a Jurid from ÜRO Parts. I tried it in all six possible orientations but it would not balance. Replacing it with an OEM flexible coupling from GKN solved that problem immediately.

Adjusting the center bearing is a trial-and-error process as you discovered, and you've probably got it just right, but the workshop manual does state that when it is adjusted properly it will be a bit to the side of the line of the driveshaft, so if your two sections of driveshaft are close to being in line with one another, the center bearing is probably not offset enough to the side. For future readers, it is a good idea to scribe the center bearing mounting brackets, bolt head locations on the brackets, etc. before removing the driveshaft so you can get the new bearing as close as possible to the position of the old one.

A few things I don't see on your list are the front dampers/shock absorbers themselves, which can fail from age regardless of mileage. The yellow foam upper bushings are a very common failure point but you'll usually hear knocking sounds when this happens due to the shock shaft banging against the hole in the wheel arch. The lower shock bushings can also fail. Have you done a basic check of the shocks by pressing down sharply on the bumper and releasing, then watching for no more than 1-1/2 rebounds before the shock dampens the movement? Have you checked the rear shocks the same way?

I assume you checked the ball joints? The lower ones in particular are known to fail and are easy to replace. Note that the screws are Imperial/SAE and not metric (I think the ball joints were sourced from GM).

How are your engine mounts? Could the engine be shifting under firm braking and causing a shift in the front subframe/steering?

How are the inner and outer tie rod ends?

Looking forward to your next update!

Cheers,

Don

 

Don B
Many thanks for your thoughtful analysis. I too have been suspecting the rear subframe bushings but didn't know what I was looking for when examining them. Come to think of it, I can hear more noise from the differential than I thought I should. You may have something there. I did a similar repair on my BMW touring I recently sold and it had a pronounced effect on handling, especially the stability of the steering. Think I'm going to order a set bushings.

For the most part, I've been sticking with Jaguar parts for critical items like suspension. Front subframe rear bushings were "clocked" as the original ones were set. I'd like to assume they were set correctly at the factory. With the front subframe out, the engine mounts looked good with no separation or cracks, so I did not replace them. Though not mentioned, I've also replaced the upper front shock bushings which were toast.

I'm also wondering whether the driveshaft center support bearing should also be adjust vertically. If the height of the transmission changed slightly with the replacement of the rubber components in the mount, then I would think the center support bearing should also be adjusted. Thoughts?

And while on the subject of shock absorbers, I will be replacing mine in the near future (when I delete the self leveling rear suspension) and am leaning towards Bilsteins. I've always been a big fan of them in my BMWs and would like to improve the handling in my XJ. Do others have experience with them?

Thanks all,
Tony

 

Follow up to previous rear subframe bushing

After reading Don B's suggestion re failed bushing, I quickly inspected mine and wondered if the above is normal. The subframe is touching the lower support bracket ever so slightly on the right side of the car. I would have thought that if the bushing had failed (and sagged), the subframe would be touching the body at the top of the picture. Thoughts?

 

Since that lower bracket is bolted directly to the body, any metal-to-metal contact between the subframe and bracket indicates the bushing is perishing and is not isolating the subframe properly.

Regarding shocks, the originals on my two XJ40s were made by Boge, and when I could find Boge replacements they were excellent. Later on I was not able to find Boges at affordable prices so I went with Bilsteins in front and Sachs in back and they were both excellent as well. My perception was that the Bilsteins were slightly firmer than the Boges, which some owners prefer. If I recall correctly, Boge and Sachs are both now owned by ZF. Other brands that I recall XJ40 owners using are Monroe and KYB, but I don't have any personal experience with them on a Jaguar.

Cheers,

Don

 

Seems my handling problem may have been the result of something rather basic: a lousy alignment. After replacing some bushings and mounts in the front end, it still darted about upon braking. Had an alignment scheduled at the dealer but cancelled when I thought I might be doing more suspension work. Then, one evening while pondering the symptoms again, I pulled out my carpentry laser level and took some rough measurements of the toe. 3/16" toe OUT! No wonder it wandered! Added a little toe in and it drove significantly better the next day. Checked it again and found my initial measurement had been more or less correct, so added a bit more toe in to about 1/8" and it now handles as I'd expect it to.

While the car was up on the lift, I also removed the transmission mount (again) and reassembled. Not certain what I did differently but even the intermittent drive line vibration is gone. Things are looking up. Now I just have to replace the crappy shocks, add a beefed up sway bar....

And so we proceed down the rabbit hole.

 

Yay! Another "easy " fix!

 

Tony,

Thanks for posting the resolution. Too many members ask a question, get advice and then leave us guessing what happened.

I've added "RESOLVED" to your thread title. There's a lot of good troubleshooting information here which will help others with a similar issue.

Graham