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.
My XJR6 has quite restless steering characteristics. Based on a visual inspection the various bushings seem to be ok. I put in new shock bushings, but the shocks themselves are old. When I lift the front on jacks and shake the tires (grab the tires and turn left and right), there is some play. I could pinpoint the play to rack and pinion, and removed the boot covering inner tie rod. I thought the tie rod joint could be shot, but actually it is the shaft / rack that has the play and moves a millimeter or two (horizontally).I would like to know if this truly is sign of worn parts or is there always such play?
A millimeter or two doesn't sound significant to me. let's her what others have to say.
"Restless steering characteristics"? Could you be more specific, please? Could you be referring to tramlining? If so, it's a somewhat notorious characteristic of the XJR6; lots of threads discussing mitigation.
Tramlining is a new word to me, but yes, it could be used to characterize some part of the behavior. Understeer is another. Maybe also wandering. I am trying to go through the possible problems, eliminate them one by one and see the impact. I started by straightening a bent wheel and balancing the tires. I did the rear shocks and I think I have to do the fronts as well. I already practiced by putting in new top bushings. I checked the play, because I want to do a wheel alignment, and need to eliminate any extra play before it. I hesitate to start changing the control arm bushings etc just to see if there is an impact. The assume the problem is a combination of several items, and I have been able to eliminate a few, but there are more to solve.
I came across the shim in some earlier posts. In my understanding the play I observed is not due to steering rack mount, it is internal to the steering rack. That shim looks like a good 3D printing project, if I ended up needing one.
Tramlining is a new word to me, but yes, it could be used to characterize some part of the behavior. Understeer is another. Maybe also wandering.
Tramlining is the tendency for the car to follow road irregularities, sometimes very abruptly. The car "changing lanes all on its own" is a common description of tramlining. It often comes down to tires as much or more than anything else, and that's true with the XJR6. Some cars just don't respond well to wide, low profile tires. Tramlining complaints are most common when the tire aspect ratio goes below '50'.
The symptoms you describe can be due, at least in part, to wear between the steering rack and pinion gears. You can often reduce the play by adjusting the pinion gear preload. On the rack pinion housing (where the steering column connects but on the opposite side) is a 17 mm hex adjuster inside a graduated ring. You don't have to mess with the small set screw in the middle of the hex. Paint alignment marks on the hex adjuster and outer ring so you'll be able to reference the original position. Then turn the hex adjuster clockwise about 1 or 2 graduation lines and take a test drive to see if things have improved. If not, try adjusting 1 or 2 graduation marks more at a time and test driving until the play is reduced or eliminated. Just take care to make small adjustments at a time. It's easy to go too far, and you'll know if that's happened if the car loses its ability to self-center coming out of turns and instead keeps turning you toward the ditch unless you turn the wheel back to center it yourself. If you get there, back off the adjuster a couple of lines and retest.
Regarding your observation that the rack can move a millimeter or two, that may be more significant than is initially apparent. Imagine a steering knuckle ball joint is at the pointed end of a slice of pie, and the wide end of the slice of pie constitutes an arc of certain width resulting from any change in the steering angle. Each millimeter of movement at the outer tie rod end is multiplied such that a change of just a millimeter might result in a difference of centimeters at the outer arc. The illustration below shows how the arc at the wide end of the pie marked by the symbol Lambda increases greatly with seemingly insignificant changes in tie rod end position. The math is way over my head, but you can read more about these sorts of issues at the link below the illustration:
Worn outer tie rod ends, ball joints and wheel bearings affect steering precision and tramlining and their effect is cumulative.
Your symptoms can also be caused by softened or perished bushings. The ones that seem to have the most impact on steering are the front subframe rear pivot or fulcrum bushings, part 2 in the diagram below. When these bushings soften or fail, they allow the entire front independent suspension, including the steering rack, to move contrary to steering inputs, and allow the front end to easily tramline in response to road imperfections. The Vee-mounts, part 3, also soften, but it's those rear bushings that allow the most axial movement:
To a lesser but still significant degree, the rear subframe bushings also have a surprising impact on steering. They are part 14 in the diagram below. When they soften or fail, they allow the rear independent suspension to rotate contrary to steering inputs or to tramline in response to road imperfections. The impact on steering precision is not as great as that of the front pivot bushings, but it's more significant than you might think. I've always been surprised at how much better the steering felt whenever I've replaced these bushings on an XJ40/X300/X308:
The steering rack bushes Parker mentioned improve steering precision further, but they won't help much or at all if the above bushings are soft or torn, or if, for example, you have a bad wheel bearing or ball joint. For more information on the steering rack bushings and how I made my own in the pre-3D printing days, see this post:
Doug i have found that more than 1 graduation mark is all you should go as 2 many times has left a bit of binding as its too tight. If really worn maybe 2. We used to tighten the racks up 1 click to help with a slight steering wheel shimmy too. moving the tire in/out at 9 and 3 should feel tight and no play. ESPECIALLY moving by hand. If you have that much play put you hand on inner and outer tie rods to feel for the play in each joint. If theyre tight and you have play, check the wheel bearings. If you can feel play in rack bushings by hand then theyre very shot or Step away from the weights Arnold.
Thank you very much for the thorough explanation, it was most helpful. I had some curiosity towards the adjustment when I was last time under the car, but because it hadn't come up in any earlier discussion, I didn't dare to touch it. I went and adjusted it a total of three ticks, which made those round notches in the picture aligned. (This picture is taken before the adjustment.) It didn't remove all the play, but to my great pleasure, the steering wheel still does center properly and I didn't end up in a ditch either. I am convinced that the play is internal to the steering rack, because I could visually see it when I removed the boot. I thought it would be the inner tie rod, but it wasn't. Of course this doesn't exclude other sources of problems, such as the bushings. I would like to remove all possible play before doing a wheel alignment.
Somebody backed that adjustment off. Those detents are punch sets . Thats why you got 3 clicks. You got back to where it started life at. Usually only 1 maybe 2 clicks at the most is all i have ever done.
Acceptable rack and pinion play
