240Z steering issues

This past race weekend, my 240Z developed a new problem. A few laps into the session, after a high speed lefthander (~100mph) almost 180 degree turn, the steering would not return to center on the straight after the turn. Was maybe 15 degrees off left. It also felt like the toe had changed in the following turns as the car was not handling like normal. The tire wear observed after session would also seem to indicate the toe was changing.

Has anyone run into this before with a Zcar? I did a visual inspection and checked for loose bolts (nothing obvious) and tried to shake all the tie rods, ball joint, TC rod, rack mounting, everything I could think of and did not find an obvious issue. I guess I will just need to basically rebuild the whole front end including the rack.

Thanks,
jeff

What you are describing is exactly what happened to me at VIR 2 weeks ago! We did not figure this out at the track with quick inspections of the steering geometry etc. but it is clearly evident in my in car video. Sometimes I could wiggle the wheel and get it to re-center, other times not. Happened most notably after a high speed series of left turns, two in a row, taken at around 70-90mph - depending on how screwed up my steering was!

When Brad and Digital Chassis had the car in for alignment he re-centered the rack and indicated the bolts that hold the rack weren't as tight as he'd like, but they weren't just falling off loose in your hand either. So that might have been it, it is hard to say. Toe settings as well as camber were all off so I'm sure these contributed to our problem.

I'll post back here with any findings we get from the next race outing. Be interested to hear what you find out as well.

R

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Ron Earp
NC Region
Ford Lightning Tow Beast
RF GT40 Replica
Jensen-Healey ITS
1/2 a 260Z ITS

[This message has been edited by rlearp (edited April 04, 2005).]

look for a crack in the outer end of the front control arm where the balljoint mounts. Also make sure the subframe to chassis mount bolts are all tight.

The solid bushings for the steering rack allow the rack to "slip" from one side to the other and get off center. I have used shims under the clamps to tighten things up. That happens regularly, especially after an off track excursion.

Another thing to look for in the future is the gland nut on the strut working loose, causing a "wiggle". I have had tie rod ends bend as well, unfortunately in a corner, which caused a snap-spin I couldn't recover from. Also expect the camber bushings to shift, causing alignment problems.

Just a bunch of z-stuff, besides stuck floats, electrical problems, shift fork pins etc. Its also a good idea on a nismo lsd to disassemble the diff and use emory cloth to scuff up the glazed plates. And check the wheel hubs for cracking.

Hell, just take the whole car apart, and re-assemble between race weekends just to play it safe.

Tom
ITS 240z

[This message has been edited by Tom Donnelly (edited April 04, 2005).]

Thanks for the info guys. All good stuff. I'll post what I find as well as I work on it this week. It does seem to be something like the rack slipping (scary thought!) as everything still seems tight and as I would go down a straight after the turns, it would slowly return to the 'home' position. I'm guessing that if the rack is actually sliding in the bushings, there should be some sort of wear mark on the rack. I'll double check for that. At the race, I tried to tighten everything I could put a wrench on. The rack mount bolts are TIGHT, borderline breaking off now, so that is not it, but the idea of shimming under the bushing might work. I also had found that the 4 bolts that hold the K member to the unibody were maybe 1 turn loose, so I thought I had found the problem at the track but no dice. I must admit, sometimes I like to curb hop, so it sounds like the rack bushings might be hammered now. It really is not acting like something like a ball joint or tie rod is bad since it is stable everywhere else and seems to 'heal' itself after a bit of a straight section.

Thanks all,
Jeff

Let us know what you find - I really found it strange that it could "heal itself" too. At first I thought a tire was overheating and somehow making it happen, but thta didn't make sense. My teammates kept looking at me like I was crazy when I'd talk about it after I got out, but Jeff saw the race video and it is very clear in a couple of places - me going straight but holding the wheel about 25 degrees or so to the left, and then it goes back center after a few turns or time on a straight.

R

Camber eccentics loose?

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"Bad" Al Bell
ITC #3 Datsun 510
DC Region MARRS Series

So I am posting this sort of real time as I look at the car, but so far:
- the rack seems tight as far as side to side. I am going to replace the bushings and maybe use a reman rack anyway.

- the left side TC rod bushing looks hammered. There is a washer on the TC rod, then an aluminum bushing, then what looks like a poly doughnut, then the frame rail horn. The poly doughnut is hammered pretty flat, and once I started poking it, some of the bushing fell out. Prolly not good http://ITForum.ImprovedTouring.com/wink.gif

What are people using for the TC rods? This kit looks like the ones you buy from Motorsport Auto. I remember seeing on this list what someone called the "crawford mono ball". Can someone elaborate?

- looked hard but so far no cracks in the K member or control arms. Camber plates are tight, eccentric control arm bushing look tight but might replace them anyway.

Jeff

What you have is the old Kontrolle style T/C rod kit that's been around since 240Z's were new. The poly squishes out on a regular basis, especially on driver's side depending on how close the headers come, and on how much you preload them. The Crawford Monoball is a spherical bearing setup made by Crawford Z Car Services in Tenn. Call Doug Stewart at 615-327-4159

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katman

Katman,

Did you ever have that problem with the steering rack? On my first z the rack would slip occasionally. Never asked y'all about it.

Tom

We never had problems melting the Kontrolle T/C bushings, but I turned one to dust when I hit a pothole off course at the ARRC a couple of years ago. I suspect that I might have bent something if the bushing did not absorb the energy.

That was the same year that David Spillman had a top 10 finish with a VERY loose gland nut. Quite an impressive drive!



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Wayne Burstein
WDC Region, ITS #10, Datsun 240Z
www.mountainmotorsports.net

Quote:

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Originally posted by Tom Donnelly:
Katman,

Did you ever have that problem with the steering rack? On my first z the rack would slip occasionally. Never asked y'all about it.

Tom

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Never had any rack problems. You can adjust the tooth engagement and you can usually feel how worn the rack is around the center point during the adjustment so you can discard those. I don't see how the rack and pinion could slip, but I can see how the splined input shaft could slip inside the yoke at the bottom of the lower steering sector. Regarding the mounting of the rack and pinion assy, let's just say we had that sucker clamped down pretty good.


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katman

Thanks for the info guys. New TC kit and rack bushing on the way. Hopefully we can get out to a test session before the next event.

Jeff

Well, bad news for me. Replaced the TC bushings (the old ones were trashed, esp on the driver side from the header heat) and replaced the rack bushings just because.

Checked the toe just prior to the session (was set to 0 toe), then about 15 minutes into a 45min race, the issue starts coming back. I nursed it through the session, but ended up cording out the left front tire. Measured toe after the session and it was 3/8" out!! Nothing easy to find like loose bolts or tie rods....

The whole front end is coming out of the car now for a complete rebuild.

Jeff

I had the same thing happen at Kershaw in the May race last year. It was the eccentric bushing spun around 180 degrees. I completely smoked a set of front tires with the toe out situation ( Still won the race, though!)
Steve Parrish
Silver Z 57

Quote:

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Originally posted by powerslide91:

Checked the toe just prior to the session (was set to 0 toe), then about 15 minutes into a 45min race, the issue starts coming back. I nursed it through the session, but ended up cording out the left front tire. Measured toe after the session and it was 3/8" out!! Nothing easy to find like loose bolts or tie rods....

The whole front end is coming out of the car now for a complete rebuild.

Jeff[/B]

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Jeff and I have looked at ours, we're pretty sure it is our rack bushings. If the tires are loaded on the ground with a lot of resistance to turning (as opposed to hanging in the air on jack stands) then when you turn the wheel we can see the rack slip. The bolts holding it were saftey wired but the bushings must be shot.

I'd tested that previously but with the car on stands - no movement. Just not enough force to push back on the rack I suppose.

R

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Ron Earp
NC Region
Ford Lightning
RF GT40 Replica
Jensen-Healey ITS
1/2 a 260Z ITS

Jeff, this is just a WAG, but it sounds like you may have a problem in the rack itself, either the inner tie rod end, or in the R&P itself (possible the adjustment is off and the rack is jumping a tooth on the pinion?) .

I'd be tempted to swap in a decent used rack (with new outer tie rod ends and bushings) for the next race and see if that doesn't cure the problem.

I've had something similar happen. The rack was moving side to side in the cradle. Made some sheet metal shims (look like rod bearing halves) and this allowed more clamping. Also, if you have offset bushings, check for tightness often, like before every session. Not sure if this is your problem, but just something else for you to check.

Dave Ciufo

Thought I would finally get around to following up on this thread FYI for the guys that said they have seen something similar.

I ended up basically replacing most of the front end parts to be safe. Ended up with new; rack bushing, TC bushings, ball joints, outer tie rods, and control arm bushings (eccentrics). I ended up taking the whole front suspension out of the car and inspecting for cracks / loose hardware / funny wear marks... whatever. Lastly, I oversized the bolts that hold the k-member to the unibody and the ones that hold the rack to the k-member so the bolts themselves are in shear instead of just relying on the clamping power of the bolts. Because of the rather extensive rebuild, I cannot say for 100% what was the cause, but I did find one thing that was an indicator I think. The original control arm bushings had the star washer installed outside of the k-member, instead of inside it (so it was under the nut for the center bolt instead of biting into the aluminum eccentric bushing). Now these bolts for the control arm were on TIGHT, but based on the wear and galling on the bushing, it looks like the eccentric on the right side was able to rotate slightly. I'm guessing it would not take alot of rotation while the car was on track to make a pretty big change in toe.

The up shot is I took the car out to a test session last weekend and put a solid day on track with it and the problem did not return. I think there were alot of good suggestions in this thread, thanks for all the advice and help.

Jeff