Odd one about front arms/severe shaking

Hi all

So after I lifted my 300 D1 (2” springs, +5 shocks, and the usual other parts) I thought I best fit some castor correction arms. Only thing is as you can see when I line up the first hole they hardly look the same as the original at the thread end which I thought they would, but I thought I would give them a go so I fitted them with a full set of standard bushes but I didn’t put a steering damper on to start with. Once fitted the wheels look ok in the arches and the springs and other things look lined up again but when test driving it feels ridiculously hard like it had no bushes and was just metal to metal right thru and every vibration of the road was going thru the whole car, and me. Also when powering out of a corner at about 50 the whole car started to shake horrifically and uncontrollably to the point where everything jumped off the dash and console until we slowed back to about 30 (I’m wondering if it was shaking it’s head like a fast motorbike without a damper) So I fitted a damper and went back out, the damper seems to be stopping the shaking but I don’t know that it should behave that badly without one and it still feels far from rite and is still sending all road vibration thru the car, and is still the same with the front prop off

So i guess I’m wondering if this is a common problem after fitting 3 degree arms or if mine are dodgy, none of the other vehicles in our group do this, I checked swivels aswell

Many thanks in advance

Towsey

Have you done anything with the panhard rod?

Changing the steering/suspension geometry can throw up some suprises ...

Check swivel pre-load and bearing, wheel bearings, all bushes and panhard rod seatings too ...

Even swapping tyres front to back can show where a wheel weight has come adrift, or a tyre has a carbuncle on the inside face ...

Thanks for replies

All above have been checked, I checked swivels with both steering bars off, panhard rod and bushes are about a month old and bolts and holes are ok, a panhard bolt did come undone once but this is nothing like that. Has anyone ever compared arms before, I don’t know how all this stuff works about not mentioning places but they came from a very common place over here and they were yellow before I blasted and did them orange

Thanks

Towsey

If you mean that you've got the new and old lined up by their first holes (at the axle end), then yes, there is a bit of a problem. The arm should be about 0.4" longer than standard to keep the axle in the same position fore and aft. Yours looks about 0.3" shorter, so your axle will be about 0.7" too far back. If you've got the standard panhard rod then that's too short now, guessing that your axle will be pulled over to one side by about a third of an inch. Neither of those though should be causing your problem, as far as I can see - I could imagine it causing a problem with a marginal length prop, but you've taken that off.

That made me think of you rear prop, what sort of condition is that in because you're running the UJs at a bigger angle change now? Is its, now slightly extended, sliding joint in OK condition? Thinking of the back again, were those definitely OK for length? Does a D1 have the A frame and is that on OK condition of its new angle - thinking vibration again?

The other thing is that the chassis bush part of your new rod is shorter, and that means that you're compressing the bush a fair bit more, and that won't be helping on the transmitted vibration - assuming you've tightened the nut to the end of the thread.... If you've got new nyloc nutss try loosening them, and if it helps then either fit a soft polybush or drill for a split pin because that's not what a nyloc is for....

If the damper helped on the twitchiness then I think you probably do have some play in the swivels, rod ends etc, so check those again. (Not wanting to teach you how to suck eggs, but how are you checking the swivels?).

Just some thoughts.

Hi thanks for that

Disco has been lifted a while I just didn’t put the arms on straight away and it’s been fine all the time until I put the arms on, and they were all I changed at that time. Yes that’s where I measured from, there’s 10mm difference between them to where the first big washer goes. I forgot to say the new panhard rod is adjustable sorry, and it has new hd rods and track rod ends about 2weeks old. Wheel bearings are tight, I’ve driven vehicles before where they have been loose enough to need a second press on the brakes but even then it’s nothing like this. All back end stuff is nearly new but the shaking started from the front, very strange and bad, I don’t mean like prop phasing type of vibration (although that is to sort aswell when I find a prop that will let me change it), it was that bad my eye balls were shaking and I couldn’t see straight daft as it sounds. I did think about, and have since, making some spacers up on the lathe and pinning the nut to return things as close to normal as possible but on that particular day I wanted to be on cos I needed to drive the disco home but I think that’s wot I will do because, as you also say, it’s all a lot tighter now due to the reduced thread length, my personal opinion is that’s where the problem is but I wanted to know wot others thought or if they had come across this before

Many thanks

Towsey

Update for anyone curious

So I’ve backed the 30mm nuts off 3 turns and it feels better, if anything a little sloppy so maybe 2 turns would of done but there’s less vibration than there was. I’m thinking play about till it’s rite then make some spacers up so there is something for the bushes to sit on and the nuts to tighten against then new nylocs or pin these and bingo...that’s the theory anyway

I know it's a bit of a faff, but it's worth getting it right - just going by the picture, a couple of turns doesn't look enough. Measure the unthreaded part of your old arm where the bush sits, and then set the front face of the back washer at that distance from the front face of the front washer. Again, by the look of it a nyloc may not get enough to grip and pinning will be essential, meaty pin too.

Don't forget that your handling is going to be less sharp because of the lift, don't try and compensate by having the bushes too tight. Or, I suppose you could,but I'd rather be vibration free and slow down a bit!

Hi, we did that before fitting and I think, if memory serves, there was 10mm difference in front faces and 13 in shaft length where the bushes sit. 3 turns is roughly 10mm and I think another 5mm and the nyloc will be off the end of the thread and definatly need pinning but this will be tried aswell. I am thinking about seeing where a phone call gets me but to be honest it’s easier to turn down some spacers and pin the nuts than it is to wait, measure, blast, paint and fit again some new ones and prob have to send these ones back, but if I can’t get these rite then...

Thanks

Towsey