Steering rack "play" options - Page 3 - Nissan : Datsun ZCar forum :Nissan Z Forum: 240Z to 370Z
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post #21 of 41 (permalink) Old 04-12-2018, 06:57 PM
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Solving your front end wobble

First of all a vibration in the front end HAS to be from a rotating mass. In other words tires out of balance, warped wheel, or tires out of round. A vibration cannot be caused from worn parts. Yes worn parts can sometimes accent the issue but it comes from the RM without any doubt. I've been dealing with this issue on z's since I first started on them back in the dealership days from 78 to 85. If your front tires are out of round .020 you'll feel it in the steering wheel. If they cause wobble at .020, just imagine how much you'll feel at 1/8" out. Most places aren't capable of testing your tires in that respect. This is one of the topics I'll be doing a write up on with pics, for my new website when it comes out next year. This year I'm coming out with a new online store finally. It's easy to test for out of round tires IF you know how. I have a sure fire test that is almost 40 years old and is 100% accurate.
As far as your rack goes the car has to be on the ground so that the rack is loaded when you move the steering wheel back and forth to be able to test adequately. Of course the rack mounting bushings need to be solid as does the steering coupler. You can grab the rack boot one at a time with your hand and squeeze it so you can feel the inner tie rod ball and socket, while someone else moves your steering wheel back and forth about 2". If you feel slop it's bad, you should be able to see the slop on the outer tie rods when the steering wheel is rocked. You can also compress the outer tie rod with channel locks to check for wear on the ball and socket too. Of course checking the wheel bearings mentioned before is important too. Sway bar may or may not be screwy, but it cannot cause a vibration in the wheel.
Keep in mind that IF you had a tire or wheel imperfection before you did hi perf rack bushings and steering coupler you may or may not have felt it in the wheel because the rack can move with bad mounting bushings absorbing the wobble. Once you lock the rack down so it cannot move then the wobble is transferred to the steering wheel itself.
If someone wants to find out how to test for tire imperfections just send me an e-mail to [email protected] Over the next few weeks I'm going to take a couple of pics of the test, and do a small writeup on it that I can respond with. It's going to be at least a couple of weeks because right now I'm moving all the parts out of 5 large storage lockers so I'm swamped. I've got 3 lockers left to move out of and the lockers are crammed full.


Z man of Washington

1978 black pearl show car-retired, I bought it new. 1983 zx turbo daily driver, modified, 3rd owner. 1970 240 #23 project car FOR SALE. 1970 240 #638 driver. 1973 240 roadster being built. 50+ other z's & zx's. 57 Chev Sedan Delivery. 79 620 King Cab. Store front
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post #22 of 41 (permalink) Old 04-13-2018, 12:34 AM Thread Starter
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First of all a vibration in the front end HAS to be from a rotating mass. In other words tires out of balance, warped wheel, or tires out of round. A vibration cannot be caused from worn parts. Yes worn parts can sometimes accent the issue but it comes from the RM without any doubt. I've been dealing with this issue on z's since I first started on them back in the dealership days from 78 to 85. If your front tires are out of round .020 you'll feel it in the steering wheel. If they cause wobble at .020, just imagine how much you'll feel at 1/8" out. Most places aren't capable of testing your tires in that respect. This is one of the topics I'll be doing a write up on with pics, for my new website when it comes out next year. This year I'm coming out with a new online store finally. It's easy to test for out of round tires IF you know how. I have a sure fire test that is almost 40 years old and is 100% accurate.
As far as your rack goes the car has to be on the ground so that the rack is loaded when you move the steering wheel back and forth to be able to test adequately. Of course the rack mounting bushings need to be solid as does the steering coupler. You can grab the rack boot one at a time with your hand and squeeze it so you can feel the inner tie rod ball and socket, while someone else moves your steering wheel back and forth about 2". If you feel slop it's bad, you should be able to see the slop on the outer tie rods when the steering wheel is rocked. You can also compress the outer tie rod with channel locks to check for wear on the ball and socket too. Of course checking the wheel bearings mentioned before is important too. Sway bar may or may not be screwy, but it cannot cause a vibration in the wheel.
Keep in mind that IF you had a tire or wheel imperfection before you did hi perf rack bushings and steering coupler you may or may not have felt it in the wheel because the rack can move with bad mounting bushings absorbing the wobble. Once you lock the rack down so it cannot move then the wobble is transferred to the steering wheel itself.
If someone wants to find out how to test for tire imperfections just send me an e-mail to [email protected] Over the next few weeks I'm going to take a couple of pics of the test, and do a small writeup on it that I can respond with. It's going to be at least a couple of weeks because right now I'm moving all the parts out of 5 large storage lockers so I'm swamped. I've got 3 lockers left to move out of and the lockers are crammed full.


Z man of Washington
Thanks for all this information, I will take a look at how the inner tie rod ends are moving (the boots are all ripped up, I can just give it a look) and report back.

Besides the slight vibration on the steering wheel at around 50-70, i can feel the car sometimes move a little to the left or right in the lane which the more I think about it just means 'go buy a rack and be done with it', right?


Sounds like you've done more than casual work on a project car?

1978 280z - stock L28 engine - Dallas, TX
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post #23 of 41 (permalink) Old 04-13-2018, 01:08 AM
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Previously, I had the impression that your car pulled to one direction only. Your latest post mentions motion to the left or right, which got me thinking that your car might be experiencing a phenomenon called tramlining.

http://www.team-bhp.com/forum/attach...tramlining.pdf

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post #24 of 41 (permalink) Old 04-13-2018, 01:24 AM Thread Starter
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Previously, I had the impression that your car pulled to one direction only. Your latest post mentions motion to the left or right, which got me thinking that your car might be experiencing a phenomenon called tramlining.

http://www.team-bhp.com/forum/attach...tramlining.pdf
Sorry for the confusion. Pulling to the right is what will happen if I'm on a straight road and just take my hands off the wheel. Unrelated issue - it will sometimes drift in the lane left/right on its own but it is not a constant issue where I have to keep correcting it as I drive.

I really think you may be onto something with "tramlining." The PDF's description of the feeling of driving through a periodic "side wind" is EXACTLY the sensation I'm encountering. I periodically look at the trees to see if it's windy but it must just be this tramlining phenomena?

Is there something I can do to fix this or does it simply call for a new rack?

1978 280z - stock L28 engine - Dallas, TX
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post #25 of 41 (permalink) Old 04-13-2018, 01:45 AM
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From some quick reading on the Internet, I reminded myself that the causes could be tires, worn suspension components, or alignment. Or a combination of these. I think the steering rack itself is unlikely.

Your comment about ripped boots on the tie rod ends make me think you should refresh your suspension, followed by an alignment, before doing anything else. But, I don’t want to help you spend your money without you getting additional opinions to gain confidence or to dismiss this possible diagnosis. After all, my opinion is only worth what you’ve paid for it.

Jim
1975 280Z, Metallic Green
Long Gone: 1975 and 1978 280Zs, both Metallic Brown

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post #26 of 41 (permalink) Old 04-13-2018, 08:50 AM
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odd handling esp at speed can sometimes be worn shocks. Often by this age the orig hardware that damps the strut has been replaced with strut cartridges. If the cart is blown (no damping or little damp due to loss of oil) then the car can float around feeling unstable.
Bouncing the corners (hard) by hand you should have NO bounding just down and up. If it oscillates at all its prob blown. This is not a definitive test, so if you have not replaced the strut carts and don't know the history, its prob due. My car would wonder around at speed (generally over 70mph) enough to get my attention, I replaced the following


ball joints (not needed but did anyway with quality replacements)
TC bushing (rubber not urethane)
sway bar bushing (rubber again)
rack bushing (OE rubber)
rebuilt strut (new o rings and replace oil with fork oil 20 wt IIRC)
rims check for run out (alum slotted mags) all had some least amt was used on the driver side frt, then pass frt then drv rear and worst was on the pass rear.
on thing left on the front was the OE control arm bush, it felt solid and was not torn.
I have a little bit of shimmy when braking, my front disc are just in spec and plenty thick so I may get them turned but not in a hurry.
Somethings to think about on yours .
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post #27 of 41 (permalink) Old 04-13-2018, 10:12 AM Thread Starter
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Alright so your guy's guess is I should look at the steering rack as a whole component moving left/right instead of the components inside the rack being the weak link (or both)?

It really can't be the wheels/tires/alignment/balancing as this has been an issue through 2 sets of rims, 2 sets of tires on each wheel and alignment/balancing at different shops all with the same results

1978 280z - stock L28 engine - Dallas, TX
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post #28 of 41 (permalink) Old 04-13-2018, 11:16 AM
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the other guy mentioned rotating mass, as the likely culprit (only really) so one last thing, how is the braking? does the steering shimmy with the brakes? Look at my video, I have a lot of side to side movement with the steering loaded. One last thing are we talking death wobble shaking or just a very light shimmy that comes and goes at the speeds 50-70, This is a manual setup that will transmit even the slightest issue. Worst part about remote diagnostics is differing opinions of the severity of the problem. Maybe a video of the issue will help.
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post #29 of 41 (permalink) Old 04-13-2018, 11:21 AM
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are the alignment shops giving you any reports back on the amount of tow? only really adjustable thing on a stock Z.
On the tires, do you have a dial indicator? I know you have taken it to shops, but I still prefer to test things myself. dial indicate the rim runout side to side and vertically with the wheel so you can spin it. see for your self. when I took my wheels to the shop I stood next to the guy while he spun up the wheel so I could see the run out. then he marked the ones for me to use in which location.
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post #30 of 41 (permalink) Old 04-13-2018, 12:11 PM Thread Starter
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When I first got the car years ago it was a death shake, but after getting the tires balanced, its just a light shimmy from 50-70 like you said.

There (from what I've noticed) is no issue with the braking in terms of pulling one way or different shakes and shimmys. I'll be able to get the car on the jack on Sunday.

I'll make a kind of 'tour' video assuming my phone will focus and see if that helps in our diagnosis struggle haha

Thank you all so much for your help so far!!

1978 280z - stock L28 engine - Dallas, TX
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