My 78 XJ6 has a new-ish steering rack (clean) in it with a reasonably heavy steering feel (definitely not the “1-finger” parking lot experience I have read about here). The on-road steering feel is quite good and I feel it will be excellent once I replace the mounting pushes with poly.
I also have a very large turning radius. Enough of a radius that parking lot navigation takes much more consideration (and reversing!) than I feel it should.
After much reading, I have surmised that a PO had replaced the original rack with the later ‘performance’ rack from an XJS. Also gleaned from my reading is that these later racks had some tab/spacer/nut that limits the travel of the rack and was implemented to stop tire rub on later cars.
I am looking for some advice before I take the rack off the car or apart.
So, finally, my question is, how can modify the rack to reduce the turning radius?
Where is this limiting device located?
Can I machine the current limiting device down and re-install?
Does anyone have some of the appropriate spacers they can sell/send me?
I can’t quite remember the details. BUT, that mean’s it’s all in the archives because I never encountered this problem myself. A search should be fruitful if you don’t hear directly from users.
I have done some digging which is how I learned of the possible rack update. The reference to the shim/spacers/tabs is noted in a few of the posts but I have not been able to find a part number, images, or clear description of what to change. This may be a result of my poor research skills.
My current best guess is that it is item # 14 in the image below.
If this is correct, it appears that I can machine off the tabs to increase the travel of the arms.
The early XJ6/XJS used 205/70-15 tires and used a flat lock plate on the tie rods. JLM-172 is the part number. When they went to a 215/70-15, a spacer was added to the lock tab about 1/4" thick. when the XJS started using 235/60-15 tires, an even thicker spacer was used about 1/2" thick. As you did not mention which rack you had, you can slice the boots off, unscrew the tie rods and remove the lock plate. Either remove the spacer and reuse the lock plate or get a pair of new lock plates. This will give you the turning radius the car originally had. Although this should not effect the toe setting, it would not hurt to have it checked when you are done. RackSpacers is an article of mine that explains it with pictures.
I see that Terry’s Jags has a couple in stock along with the poly rack mount bushings. I am working on purchasing these although shipping to Canada is proving to be a pain (expensive).
the later “performance rack from an XJS” really is an entirely different steering rack supplied by ZF. If there is really a late XJS ZF steering rack installed, there should be some tag identifying it. And if it is, you should consider yourself very lucky. I’d be more than happy to replace the original and always prone to leaking rack for such a piece - unfortunately they are very hard to get your hands on and installation requires some modification along the pipes and the lower steering column for SII cars.
So, while it would be a good idea to keep your steering rack, you could reset the spacers from the XJS sportspack condition (fitted to suit the widest rims available for XJS cars as described by Dick Maury) to the standard XJ setup.
Parts arrived last week (poly rack bushing and thin spacers) and I had a few hours in the garage over the weekend. Re+re rack with new bushings and replaced spacers was a little more work than anticipated and took 8 hours (note for future readers).
Rack is the standard Adwest unit (not ZF, thanks Jochen) and my current theory is that a PO had the valving changed in the pump to reduce assist at some point. Everything works well with nice feedback on the road although parking lot maneuvers require 2 hands.
The shims make a dramatic difference the car now feels nimble in parking lots!
The rack bushings feel slightly better but I have not been able to do any spirited driving which highlighted my concern a couple of weeks ago.
Next issue, my steering wheel moves +/- 5 degrees before my wheels move. All linkage and joints are tight.
In retrospect, this probably contributed to the unnerving experience that launched this remediation effort. I was traveling at speed (+/- 100km/h) downhill on the inside lane of a long sweeper and the car beside me drifted into my lane. In an effort to move over I corrected the wheel slightly with no response, I then corrected more with a significant response which lead to some very uncomfortable “wobble” as corrected the other way. I repeated this cycle until settling the car down. No one was hurt and no loss of paint.
In any event, I plan to adjust the pre-load on the rack as per the manual. The manual describes “knocking on rough surfaces” as the only symptom that requires pre-load adjustment. Have I missed something here? My understanding is that preload tightening should remove play from the steering wheel. Any thoughts or suggestions before I get back under the car?
in case you did your homework right - and I suppose you did - the usual suspect is the standard rubber steering rack bushings that typically cause the rack to move in the bushings under load instead of the wheel on the tarmac. If you ask someone to turn the steering wheel on a stationary car you may encounter more than one centimeter of play in the rubber bushings before the front wheels actually turn in. Stories abound that TÜV engineers in Germany insisted on the bushings to be replaced because they considered that amount of play unsafe. Yet, it was Jaguar standard. That being said, I still have the (replaced) original rubber bushings and, while my Spitfire’s steering certainly is more precise than the Jag’s a situation like you describe sounds pretty much impossible on my car.
Even Jaguar indicated that spirited driving required more precision for the steering rack though. Again the parts catalogue of later XJS cars has a solution: it is the Jaguar sports pack steering rack bushing - considerably priceyer than rubber, but renowned to be perfect and lasting, much better package of precision, comfort and longevity than the common poly steering rack bushings. Check out the postings of Gregory Andrachuk - he explained the replacement in detail and named the correct part no.
From your last post I’m a bit unsure whether you replaced the steering rack bushings with poly prior to the incident? In theory, new poly bushings should do away with the play, but chances are your parts didn’t fit precisely and are moving on the rack explaining the serious malfunction.
Good luck - but only go back to the open road once the issue is fixed!
Yes, I did replace the bushings with poly. The steering is better although I was unable to test at high speed.
Even with the new bushings, I have some play in the steering wheel. I think this may be some lash in the steering rack. I am hoping to get some feedback and insights before I attempt to tighten the preload.
Follow the shop manual for adjusting the rack pre-load. If loose, it can cause play. If to tight it can bind and even lock up. Don’t just tighten it, set it properly. Your problem sounds like to much play in the bushings .If they are still loose, then correcting that would be the first course of action.
I’ve just had these collapse on my car. The “bush” part - between the cylindrical surfaces - is fine but the larger radius outer sections on all six poly bushes have failed. I turned out of our street recently to find that I had to wind on a further 90 degrees to make straight ahead. Drove home and found all six destroyed. I guess they had been disintegrating over six years since I replaced the standard system. Like boiling a frog, I expect. The destroyed items are of unknown manufacture. I am replacing with SuperPro bushes - made locally. Hope that they are good!
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My understanding is that preload tightening should remove play from the steering wheel.
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Preload adjustment both vary the friction in the rack, dampening roadwheel feedback to the steering wheel - and vary the distance of the rack from the pinion, to compensate for rack/pinion wear. Which is is most pronounced around the center position - and leads to play in the steering wheel. When adjusting the preload; lift the roadwheels off the ground - and turn the steering lock to lock. Ideally there should be even resistance throughout - any binding out of center implies center wear…
As steering wheel is turned and (basically road wheel) resistance to turn is detected; valves are immediately opened in the pinion assembly - applying hydraulic pressure to the rack…power steering…
With no steering wheel resistance, play anywhere, valves do not open. When slack is taken up; power steering suddenly comes on and equally suddenly disappears when steering wheel is moved back. And there is a a loss of control…
As Jochen also says; first step is to observe the rack with steering wheel input with or without engine running - there should be no(!) rack movement. If the rack moves; something is wrong with the bushings/rack brackets - and preload adjustments are unavailing…
Also; the steering wheel is mechanically connected though the universal joints, pinion, rack, track rod ball lints and steering arms to the road wheels. Any slack in these components will cause steering wheel play - which must be identified and rectified before preload adjustment…
