'96 855R, Feel a clunk in the steering wheel

[MrPc]

I'm trying to track down something that must be loose in my 1996 850R, with 148,000 miles.

I can feel a clunk in the steering wheel. It occurs when coming to a stop, starting from a stop, and occasionally in the middle of a hard braking turn just as the braking forces are released in the middle of the turn. I can't really hear it, but it feels like a momentary relaxation in the steering wheel. The steering wheel itself doesn't move up or down or in or out, but the sensation is almost as if it does. It is usually felt at slow speeds. The car otherwise drives, handles and tracks well, and I don't feel much if any vibration when I'm inside the car.

I recently replaced pretty much all of the front suspension: control arms, struts, strut mounts, spring seats, outer tie rods. While I had the steering knuckles off, I replaced the cv boots and serviced the joints.

I've also replaced the passenger side lower engine mount, the transmission torque mount, and the torque rod bushing.

The steering rack is bolted down tight. I've re-checked/tightened all of the suspension fasteners, including the end links. The subframe bolts are all tight.

So...it seems that the only parts remaining are: inner tie rods, the firewall engine mount at the other end of the torque rod, and subframe bushings. The firewall engine mount has small cracks in it, but looks functional. I'm not sure how to test the subframe bushings. From IPD's article, http://www.ipdusa.com/techtips/10105/do ... s=P0,P8969, it sounds like I would be having more pronounced handling problems if they were bad (although their website does mention them being the source of "unidentifiable clunks").

I don't feel any play in the inner tie rods, but I'm not sure I'm testing them right. If I leave one wheel on the ground, wiggle at 9 & 3, look for lost motion, I can feel none, but I think I can sometimes hear a faint clunk, which sounds like it's somewhere in the steering rack area. Often the wiggle will produce a clunk from the cv joint as well. But I can't feel anything. Some websites describe a test where you disconnect the outer tie rod from the knuckle, and check to see if the inner joint is stiff enough to hold it steady without sagging--I haven't tried that.

The clunk I'm talking about is really quite minor. But it doesn't feel right, especially in a car as nice as this, and especially with so many new parts. I would appreciate any suggestions about how best to proceed to diagnose and fix this....

Thanks!
Paul

[JimBee]

I know exactly what you're talking about. I have it in my '96 850 base 5 speed 138k miles. It doesn't seem to get worse, just is there often.
It was up on a rack today and with a tech I looked around underneath, main mounts seem okay, though the front underside torque mount bushing is shot. I don't know what else it could be. Nothing seems loose. If you figure out what's causing yours please let me know

[MrPc]

JimBee, I saw a couple of your threads from last summer--I was actually hoping that you'd be able to chime in and let me know what the fix was!

The front underside/transmission torque mount on mine has been changed, the old one wasn't quite shot, but did show some cracking. It shifts much smoother now (mine is automatic). I changed the upper torque bushing shortly after. For awhile I thought the problem was fixed, but it's not...

Thinking out loud, the culprit ought to be something that can shift under changing torque/braking load and transmit the shift as a momentary change in steering force to the steering wheel.

Subframe: could shift back and forth with engine loading and braking, as the engine pulls subframe forward which then pulls car forward, and then works in the opposite direction when braking. This would change the location of the steering rack relative to the steering wheel, which might be felt as the wheel moving up/down/in/out.

Tie rods: Torque from the driveshafts, and braking forces would tend to make the wheels toe in opposite directions if there is any play in the tie rods. The transition might be felt in the steering wheel as a momentary change in pressure, especially if the wheels aren't pointed straight ahead. This might also explain why the clunk can be felt at very low speeds, just as the car comes to rest and everything relaxes.

The steering pump is full, and the fluid has been changed. Could anything be going on inside the rack itself to possibly explain this? It's not leaking...

Can anybody see any faults in my logic? I'm thinking that the sag test on the inner tie rods will be my next move, unless anybody has any advice to offer.....

JimBee--what condition are your tie rods in?

[JimBee]

MrPc:
I believe my tie rods are tight. I have about 4000 miles on the Pirelli P6's on the front and they still look new with no uneven wear.

The subframe shifting a bit seems like the most probable cause, but the bolts are all tight, including the center bolt, and the bushings frame-to-body appear good.

I do have a slight leak in the steering rack. It doesn't drip, but there is an accumulation of sludge and dirt along that back edge of the subframe.

Well, I'm still puzzled. I've decided not to worry about it unless it gets worse.

Again, if you figure it out, please let me know what you've discovered

[MrPc]

Here is an update.

I changed the inner tie rods. While the steering boots were off, I found that by pushing hard up and down on the rack, I was able to feel a small amount, about 50 thou, of radial play. It was a very small amount, but the transition time it took to move across the slop felt very similar to what I am feeling in the steering wheel.

Is any radial play in the steering rack normal/allowable? The rack doesn't leak at all. Looking at the exploded parts diagrams, it isn't clear to me what parts are responsible for controlling the radial position of the rack. The rebuild kits I've seen on ebay don't seem to contain a part that addresses this. What am I missing?

FWIW, the new inner tie rods didn't affect the clunks in the steering wheel, but made them much more consistent. I think this is because the extra stiffness in the joint at the rack end drives the rack across the slack more definitively. It generally occurs whenever the torque-steer changes directions, but not always; I suppose it depends somewhat on the relative loading of the front wheels as the suspensions position would affect which direction, up/down, the tie rod is pushing the rack. Also, the mechanic who did the alignment agreed with my assessment that there was no play in the ball joints, control arms, etc, and that the rack was bolted down tight. He discounted the "loose subframe mount theory", saying symptoms would be much worse if those were loose.

Is any radial play in the rack normal? If it's normal, does it explain the clunks I'm feeling or this there something else causing it? If it's not normal, is there a way to adjust the slop out, and why doesn't it leak? Do the rebuild kits address whatever is worn in my rack? ie would a rebuilt rack be certain to be slop free? I would appreciate any suggestions!

Thanks,
Paul

[dosbricks]

Paul, I have this also on the 850 w/157k but not on the S70 w/222k. I have replaced most of the parts you have but to no avail. I notice it most at one particular stop I make that precedes a right turn. I feel the exact symptoms you describe as I start forward into the turn. I have also had it up on a rack and it was pronounced as everything tight except slight play in the inner tie rods. Maybe the culprit is actually the steering rack. I wonder how many other 850s out there exhibit this behavior?

[JimBee]

Paul. Thanks for the update. You've eliminated a number of possible suspects. As an aside, all 3 of us describing this quirk have '96's.

Your theory about "radial play" sounds intriguing. If by that you mean minor play between the teeth of the rack and pinion gears, that might explain it. Suppose there's a slight uneven torque on the front wheels, a force might transfer up through the linkage to the union at the end of the rack, pushing it one way of the other. When the slack is taken up we feel a slight movement in the steering wheel. Seems plausible. Is it a reason to change the rack? What do you guys think?

[MrPc]

JimBee, minor play between the teeth of rack is not what I'm describing. What I mean is could move the ends of the rack up and down--not in and out. But the idea is still the same. If the tie rods are not perfectly lined up with the rack, then torque steer forces will tend to push the rack up or pull it down depending on whether you're accelerating or braking, and depending on whether one or both tie rods are above or below the rack. ie when the rack moves up or down, the length of the assembly changes suddenly as the slack is taken up. I think this might be what I'm feeling in the wheel, as the sound I could "feel" when pushing on the rack was very similar to what I could feel in the steering wheel.

It would be interesting to find out if either you have any slop in your racks. It is difficult to see it with the steering boots on....

In the meantime, I have a pdf of a brilliant "rebuild your own steering rack" write up that I'm trying to find the original post for. In it there are a couple of parts diagrams and disassembly photos. From what I can see, the parts responsible for locating the rack in the unit are the left hand plastic rack housing plug, which you can see when the boot is off, another plastic spacer in the middle of the unit near the inner rack seal, and the rack balancing block/spring assembly. None of these parts are provided in any of the rebuild kits. I'll try to find that post so you guys can see what I mean...

Paul

[erikv11]

Sounds like a bad control arm bushing, or maybe a sway bar end link is not tightened all the way.

[MrPc]

Agreed about the control arm bushing. I was hoping that this clunk would disappear when I changed them, along with struts/seats/mounts, tie rods and end links. But it remains. I rechecked all the fasteners for tightness--the ones on the end link two times. It appears dosbricks has changed many of the same parts, and if I'm not mistaken, I recall from another thread that JimBee changed some of them as well.

So...I'm looking for something else that must be loose--but not too loose...