MORE....... Steering Woes

[Screwy]

Heres the deal.

Ive got the ORI high steer on my SOA MQ.
Its got a Return to centre dampener on the draglink and its reverse tapered so nice and straight.
I had no bump steer or steer shimmy.

UNTIL.........

I reduced the number of leaves in my spring packs and thus lowered the chassis hieght about 3 inches.

NOW.........

I drive along and i get a constant steering shimmy about 1 inch side to side, and when i hit a bump at just the right way ( usually at speeds less then 30kms ) the steering goes APE and shimmys back and forth about half a wheel turn and cant be stopped until u are slowed to nearly stop and then it goes away.

THIS happens when u have lose front U - bolts, which i dont.

SO.......

I fitted a second steering dampener ( brand new standard one not return to centre ) and it gets rid of that problem. Though i can still feel it wanting to start vibrating but its not bad enough to affect me majorly, its only a constant 1 cm steering shimmy ( which is annoying ).

BUT, now my steering is stiff.
To give u an example, Most cars when u turn around a bend, once leaving the corner will automatically return the steering wheel mostly to the middle. Mine doesnt. I have to steer back out of turns as the steering wheel holds exactly where i put it.

Also, when i am sitting still or near still, i try to turn the steering wheel and the power steering pump shreiks when i even try to turn it slightly until i start moving.

It didnt do this with 1 dampener on, it only shreiked when at hard lock.
Im running 38's so maybe understandable.....

The other thing i tried:

I losened the valve on top of the P/S box and re tighten the nut and went for a drive, the stiffness seemed fixed for about 200 meters, then went solid again.....
There is fluid in the pump......

What could the problem be here?

a mystery?

this is a hard one.........

cheers for any help.

Screwy

[92mav]

the screeching may be a loose power steering belt .
Do you have extended shackles?

Brad

[V8Patrol]

Jeff,

The second damper you fitted is obviously overiding the RTC damper and in doing so not allowing it to work correctly. This idea is backed up by the fact that your pwr str is squeeling under the slightest load of turning.
I'd suggest removing the 2nd damper and testing its ridgity, it may have suffered a seizure and therefore not allowing any movement. If its ok then I'd be looking at the RTC damper for the same thing. One of them has failed for sure.

Kingy

For the other readers.....
I fitted this system to my rig some time ago now to stop the shimmy, I ran it purely as a test and its success was instant so it stayed and is now a permanant fixture.
The RTC damper is fitted to the top steering arms from the steering box side of things and simply put " it replaces the std damper". The damper which was fitted here was then fitted on the tierod link ( the big long one between the hubs), The conections are straight forward with one end ataching to the tierod link and the other end atatches to a bit of 40mm angle which is bolted to the swaybar mount on the diff.

The second damper has reduced "feel" through the steering wheel when driving but only slightly, the steering isnt any heavier and there is NO shimmy nor any sign of it. People tell me I havent "fixed" the problem simply covered it up, well I dont care ...... it doesnt shimmy any more so in my book its fixed !

Things I have tried to "fix" the shimmy problem .......
fit new .....
wheel bearings
spring bushes
tierod ends
steering damper
these stopped it for a few days but then the shimmy was back....

So I altered the
castor angle 3 degrees through to 15 degrees
camber angle
steering ratio
fitted different offset rims
tried different tyre widths with the different rim offsets
None of these did the trick either, minor improvements only but the shimmy was still there !

In frustration I
did a full spanner tightening check
rechecked the wheel bearings
fitted less aggressive tyres
altered air pressures
and still no major improvements.........

So I fitted....
the 2nd damper and the shimmy has been gone now for a year

In my book its FIXED

[Rosey]

hey screwy,

strange problem, not to sure why your getting that, mine is driving excellent now I have the dampener fitted. One thing I did do is remove the shims (top and bottom) between the caps below where you mount the hi-steer arm (king pin hat?). I did this because my knuckles where very easy to turn on one side which apparently can contribute to steeering shimmy.

The 38's could be the reason for the power steer problem. are these 15" wide?? Try pumping them to 40psia and see if your problem goes away

all your tie rod ends are in good nick? not to much play?

hope you get it sorted
cheers

[V8Patrol]

The weird thing is that no-one seems to get the shimmy till about 2 or 3 months after any mods have been made......

This has happend to just about everyone I can think of
Everyone has a great steering setup initally then it happens......
Everyone says its at the same speed....75kph......
Everyone says it happens without warning and cant be duplicated by redriving that same corner 50 times !
Everyone has different ideas as to the hows and whys

Like I said we try all the combinations to fix it but its still there, once we try and fix it we have limited success for a day, a week, a month but then it starts again.....

Yours will do it soon enough Rosey ...... in about 2 months time I recon !
When it does it will frighten the absolute cwap out of ya !....

Kingy

[Rosey]

i hope for my sake your wrong...

there must be an explaination for it!!

ballancing your tires?

[planb]

sounds like when you dropped some springs from your pack, you dropped the susp lift and affected the castor. this would explain the return to centre, or lack thereof after cornering.

how many degrees of positive castor are you running ?

and did you adjust your drag link after you lowered the vehicle ? or did you just remove the steering wheel, straigten it up and bolt it back on ?

in my opinion you shouldnt need to run a steering damper at all, let alone two. and steering dampers will never fix a problem that is eslewhere in your steering/susp set up, it will just help disguise it.

[nischev]

Just a thought could the shimmy be cause by the reduced amount of leaves allowing the diff to "walk" a bit back and forwards therefore causing the shimmy.

[Screwy]

OK,

well after some more playing around, still no better off.

i think im running 7 degrees castor on the front and had no problems until i dropped the suspension lift back down, but the castor on the front end looks good still, its only the rear that the castor is out by miles!!!!

I have no doubt of the cause of it.
It was perfect for a few months after SOA, then went stoopid, then i fixed it and was peerfect, and now i lowered the springs and it farked it.

The cause this time is that the springs are low enough on the front to Throw out the steering angles and its causing it.

All balljoints are brand new ( 100kms old )

Kingy,
the second dampener is brand new like last week, ive only driven 7km's on it. and the RTC still works as i tested it yesterday.

I BELEIVE THE STIFFNESS IS CAUSE BY THE PUMP BEING FARKED!!!

But thats not my concern atm, ill test that later.

From what i can see the only way to fix this problem is to put a non adjusted diff back under it to get the steering back straight again, though i dont want to do this....

The other soluting is to add leaves back in to the same as what was in there before, but then i lose flex........

Possibily remove the extended shackles on the front to get the angle back a touch?

uuummm the front diff wouldnt be wondering at all as there are still enough leaves in there and this isnt the type of thing that is constant......

Its almost soo scary when it happens that it makes u want a tow home, if ya havnt experianced it before.

ROSEY there is a big chance it will happen to u exentually, and the cause of you problem will be ur tie rod ends will be fawked because of the high stresses on the new angles.

WTF do i do?
gotta drive a 1000kms next month on it.....

screwy

[V8Patrol]

Fit a new pump for starters .... I have a spare here

Fit the 35's back on and test .... might be the swampers ( I doubt it tho)

Remove the extended shackles and fit an extra leaf ....

Its all trial and error form here on in

[Rosey]

could you be running far to much castor? doesn't your steering normally get twitcher as castor increases? So a small shimmy could be causing masive probs? just a guess, probably no merit.

I'm running origional castor, ie. my spring perches are parallel to the factory ones, puts the front drive shaft on big angle but steers good at this stage.

When you played around with your knuckles, nothing has been affected which could cause the shimmy?

cheers

[Screwy]

NO, the front diffs castor is still really good, perfectly straight with the driveshaft. Couldnt of dont a better job myself, and the knuckles have been rotated properly. I have no problems there.

It is definatly the drop in leaves thats cause the bump steer......
And i believe the pump is farked.

Will switch it with the one on my desiel after trials.......

Possibly may remove the shackles to some benefit.......

Kingy, i know u have a spare, i gave it to ya last week

cheers

[dow50r]

Jeff
I had this problem with a 60 series, and it was the caster that makes the s/w shudder from side to side and the gearstick hit your left leg....had the caster fixed, problem went away.
What is different here is that i went up and you have gone down...(i presume this)
Andrew

[Screwy]

Well when we lifted this, my castor was increased to 7 degrees.....

Then ive lowered it back a coupla inches, but the front shaft was slightly broken back angles prior, and now its sitting perfect with the drive shaft.

The only way castor can affect steering is by the steering angles being farked up, and mine are all perfect from what i can tell.

My first step is toe replace the powersteering box and pump, and tighten up the wheelbearings.

Then ill get a balance and wheel allign, including adjusting the tierod ends to the correct position.....

Then comes the next step which would be re adjusting the front diff, or replaceing the housing and re doing the SOA on the front end.
This option i dont really want to know about...... as least ATM.

cheers

[V8Patrol]

refit the front shockers for starters


Kingy

[Screwy]

getting there

Concentrating on The LPG dramas atm, then ill be throwin 2 weeks ot time into the stocker for trials and sale following.

[Wendle]

my theory is because your shackles are at the front, removing leaves and thereby flattening out the springs has given it more castor, which you backed up by saying:

but the front shaft was slightly broken back angles prior, and now its sitting perfect with the drive shaft.

what you have is castor slap, the front tyres are trying to return to centre so aggresively (because at that amount of castor they are trying to lift a LOT of the vehicles weight to turn) that they set up a dynamic unbalance (due to the vehicle rising and falling as they try to track straight) and that gets the castor slap going. it is also why your steering feels so heavy, you are manually trying to lift the front of the truck when you turn the wheel. allthough your steering pump/box way well be fawked as well.

and don't use your tailshaft to determine castor. put an angle finder on the top trunion bearing cap.

[planb]

sounds like castor slap to me. i thought you did a shackle reversal but ?

maybe now is a good time

[Screwy]

I havnt done a shackle reversal, though Wendle u are the first person to actually call that 'slap' a proper name, so arms up to u

Maybe shackle reversal may be on the cards?
i had 7 degrees castor before.

Now the chassis has dropped causing the top of the shaft to come down and make my agles perfect on the driveshaft.

The only place that could of affected the steering then i did the springs was on the pitman arm/dragling isnt it?

The diffs angles havnt changed.

Its the chassis thats come down, so only the arms off the steering box can be affected by the springs being lowered......

????

IM even more confused

[Wendle]

IM even more confused

think of it this way;
let's assume your chassis was parallel with the ground before you started. then you took leaves out. let's assume it is still parallel with the ground but a few inches lower. as it has become lower the shackles, infornt of the front axle, have flattened out. this means that the front spring eye is closer to the chassis. while the rear spring eye, which is fixed, remains unchanged in height compared to the chassis.
so, we are assuming that the chassis and earth are parallel, so the difference in how the spring is sitting (which also determines the castor angle of the front axle) in relation to the chassis, is also in relation to the earth. that's why you have gained more castor.
a shackle reversal will make it drive nicer, as the steering isn't going to be pushing the shackles side to side quite as directly, but it is also going to give you more castor if you don't change the spring mounts on the axle. i know fawk all about MQ's, but i know that the MQ knuckle geometry is the same as the GQ knuckle geometry. you want to shoot for about 3deg of castor, with very tight steering linkages, and quite a lot of preload on the trunion bearings. that, in conjunction with your shackle reversal, will drive quite nice. if your springs are really soft and flexible a panhard rod will work wonders too.

[Rosey]

and if your throwing in a panard rod you may as well add a couple of coils haha coily MQ...we wish

sounds like you've got some work ahead of you, can you just adjust with spring wedges? good luck

cheers

[Screwy]

Spring wedges will adjust castor about 4 degrees......
Ill get a measurement of the castor and then go from there as to whether i can just put wedges in or i need to go shackle reversal, as im not cutting those perches off an re welding them unless i have to.

Great advice Wendle, cheers.

[OffRoad Industries]

check your spring and shackle bushes

[Screwy]

check your spring and shackle bushes

i wish it was that simple, im talking about 4 inches of side to side movement if i hit a bump the wrong way..................
Even if i had no bushes i wouldnt get the amount of movement i have.
So yeh a little past that stage im afraid.

im leaning towards it being castor.....

cheers