Death wobble journey

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jonfromhamilton
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Death wobble journey

Post by jonfromhamilton » Sun 21 Jun, 2020 11:20 pm

Just going to post up some stuff I'm doing to see if my death wobble can be improved.

So I pulled the break discs down and checked all the king pin bolts they're all firm and no detectable movement in the ball joints and they move freely.
Going to sleeve the tie rod that goes between the two knuckle arms although it seems sturdy as anything already.
I did not that two castellated nuts for those joints were finger tight but the one on the steering box arm was tight still.
The big but with the split washer holding the pitman arm into the steering box spline was just holding on.
There is ps fluid coming from the input steering spline side of the box which I may end up investigating if I pull my radiator out and get a ps hose made.
So far there is no decernable play anywhere

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gwagensteve
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Re: Death wobble journey

Post by gwagensteve » Mon 22 Jun, 2020 11:42 am

Firm and no movement might still be far too loose for the kingpin preload. Confirm it’s to factory spec
Confirm condition of knuckle seals. (Kingpin preload needs to be checked with the seals removed anyway)
There should be no need to sleeve the tie rod. It’s the drag link that seems to contribute to the problem.
Yes obviously all fasteners need to be torqued to spec
Confirm steering box isn’t excessively worn by checking preload can be achieved through adjustment.
michaelpiranha2000 wrote: The rear is in great condition. but has a broken crown wheel and pinon

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neofitou
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Re: Death wobble journey

Post by neofitou » Wed 24 Jun, 2020 8:31 pm

You would be surprised how much preload the hubs need. its >2Kg with the seals off.
Also, check what your caster angle is.

jonfromhamilton
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Re: Death wobble journey

Post by jonfromhamilton » Thu 25 Jun, 2020 10:17 pm

how would you check castor? And there is no adjustment possible as far as I can imagine without some serious modification to the diff housing.
I'm not sure it would be possible to even check or measure castor.
I'll have a read of the manual this weekend

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gwagensteve
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Re: Death wobble journey

Post by gwagensteve » Fri 26 Jun, 2020 6:40 pm

It's actually not that hard to check caster. There are a few ways but the quickest/most accurate "home" method in my opinion is to level the car at ride height on a flat surface (easiest with, for example, the same height axle stand under the axle all round), and take a front spindle off. run two long bolts into the top two spindle bolt holes in the knuckle and plonk an angle finder across them. Voila!

Caster can be adjusted using caster wedges between the spring and the spring pad.

However, if you're running stock shackles and the car is reasonably level front to rear, caster should be close to standard. Whilst in my opinion stock caster is inadequate, it shouldnt be triggering death wobble.
michaelpiranha2000 wrote: The rear is in great condition. but has a broken crown wheel and pinon

jonfromhamilton
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Re: Death wobble journey

Post by jonfromhamilton » Sat 27 Jun, 2020 5:06 pm

I thought castor was east west rather than north south so thats why I thought it was just set with the angle of the kingpins but I see your point!
$60 from LROR so I will do some other stuff first.
Found an old auszookers thread on this sort of stuff and the guy ended up having his bushes at the rear of the front leaves shot so I put the car up on the chassis and going to pull the springs out tomorrow
I think I might need to remove some shims from the king pins though because with the seals in I would say it would be close to 2kg so I will pull the seals and felt out tomorrow after giving the knuckle some soap and water and see if I can do something there.
I am also thinking about welding a bit of flat bar across the front of shackles to minimize any sort of side to side movement. seems like it should be something from factory, I know when the car is flexing it would allow for the diff to pitch but that's what bushes are for and I don't like the idea that a bolt should be on angle to the bolt holes either.

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gwagensteve
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Re: Death wobble journey

Post by gwagensteve » Sat 27 Jun, 2020 5:54 pm

Condition of the spring bushes is one of those things that can contribute to wobble but can't start it. The cause of wobble is inadequate damping at the knuckle, and this is spelled out clearly in the FSM, which specifically deals with wobble.

If the stock shackles are in good condition they can't have any side to side movement - the pins are pressed into one side and on the other side there's a step on the pin so with the nuts tight there's no flex there.

If you have home made shackles with no centre bar and 1/2" bolts, yes, it's worthwhile bracing the shackle to prevent movement. It still won't be the cause of wobble, but it will improve steering response and bushing life.
michaelpiranha2000 wrote: The rear is in great condition. but has a broken crown wheel and pinon

jonfromhamilton
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Re: Death wobble journey

Post by jonfromhamilton » Sun 28 Jun, 2020 9:40 pm

Kingpins are definitely loose so I will be removing a whim on each side.
I would say there is probably half the tension on them there needs to be ie. 1kg at the pitman hole.
I will still check the bushes while then wheels are off an then put it back on the ground.
If that still gives issues I will do the drag link then the shims

jonfromhamilton
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Re: Death wobble journey

Post by jonfromhamilton » Sat 04 Jul, 2020 10:20 pm

Removed one shim and the load is fine.
The FSM says you should have equal shim width top and bottom so I'm thinking I need to buy 4 0.1mm shims now if I am removing 2x 0.5mm ones (per side)
That's a chunk of money and waiting time so I'm thinking of just getting some shim material instead.
Question... Is it terrible to just remove the top or bottom shim and drive on it like that?

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gwagensteve
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Re: Death wobble journey

Post by gwagensteve » Sun 05 Jul, 2020 8:28 am

No, no problem doing that.
michaelpiranha2000 wrote: The rear is in great condition. but has a broken crown wheel and pinon

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