desperate help needed with shocking steering shakes

[chevJ40]

im in a headspin over this stupid truck ive had my 40 series for 2 years and have alwasy had this stupid shake in the steering

it happens intermittently at varieing speeds generally caused by small bumps in the road and is violent when it happens the steering wheel rips from my hands goes side to side sometimes to the extend of lifting up the front wheels so slightly the only way to stop it is to slam on the brakes and slow right down occasionaly i can really hit the loud pedal and it goes away

since ive had it ive changed
springs
shackle bushs
shackle mounting points have been moved forwards
changed the steering dampner
wheel bearings
cvs
draglink tie rod ends
ive had numerous wheel aligns and wheel balances
nothing has stopped it

the car has power steering and reverse shackle front end the only thing thats ever stopped it is putting my 36 simexs on with 15x8 rims
i run 35 mickey thompsons with 15x10 rims on road (thats when it shakes)

i think steering box may be cause any other opinions would really be appreciated
cheers rob

[simkell]

have you checked your swivel housing bearings/ bushes. also what is the caster setting. out of balaced or warped rims? any of these might cause your wheel to shake. also check for a bubble in one of your tyres.

[plowy]

have you adjusted the bell crank at all

[chevJ40]

i have replaced the swivel housing bearings when i did the cvs like 3 times this may sound stupid but wehat is a bell crank

[dumbdunce]

is the vehicle sprung over or under? does it have crossover or standard steering?

it is probably a combination of bad caster cdaused by the shackle reversal (and spring-over axle conversion?), the scrub radius of the wide wheels, and some extra from the positive camber forcing the outer shoulder of the tyre into contact with the road.

what I would do:

first ensire every spring bush and tierod end is tight, make sure the steering box is adjusted, no slop in the bellcrank, ie everything TIGHT. then get it on a wheel aligner and find out the actual numbers for toe, camber, caster and steering axis inclination. those number will tell you what, if anything, needs adjusting (toe and caster), and what, if anything, is bent (camber, SAI). It is also worth finding out how big the scrub radius is with the wider tyres on, you can do that yourself just by jacking it up and watching - if it's more than about 1/3 the width of the tread it may well contribute to the wobbles.

cheers
DD

[chevJ40]

its not spoa and the box has about an inch or 2 of free play that from the steering wheel though

[plowy]

id tighten the box first the bell crank is the steering linkage on the rhs at the chassi rail n first cross member

[plowy]

the max ellary manual says u should have a maximum of 40mm steering play

[lance475]

A mate had the same problem with a GQ and it turned out to be the Panhard bushes.

[plowy]

no panhard rod in a leaf sprung car

[chevJ40]

the bell crank is adjusted and the steering box is pretty much as tight as she'll go thats why i was thinking it may have been the box
its s scary theing when it happens and the looks i get when it does happed geez its dangerous

[dow50r]

Dood
If your bus is up 3 inches or more, your caster will be out, and this will cause the gearstick to hit your leg when the vibs start,, sounds very farmiliar to me....its the caster....you need to swivel the diff back towards you by using tapered plates or similar.
Andrew

[RAY185]

Agree with dowr50r here, sounds like a castor problem. Although its wierd that it doesnt do it with the 36 inch tyres (if I read that correctly). When I fitted extended shackles my 40 was very vague in the steering when I went over bumps and tended to wonder a bit. I never experienced the shakes though. Either way a simple trip to the wheel aligners will tell you if you have a castor issue. If its out find out by how many degrees and you can buy the appropriate degree castor correction plate (wedge) to correct it.

Ray

[chevJ40]

thanks heaps guys that will be tomoros job but as u say its strange it only happens on my 35s not the 36s

[-Richo-]

not much help but i have been trying on some mates tyres lately, and i got what sounds like your problem when i tried my mates 36 swampers, around about 50 k's it would start to wobble and then progressively get voilent to the point where i would have to stop. It wouldnt always happen straight away i could be doing 50k's for a bit then it would just go nuts as if some kind of harmonic vibration was occuring ive got no idea what would of caused it, i had no dramas with 35 simex's and ive been running 33 mtr's for the last 2 years without a prob. All i could put it down to was something wrong with the tyres and something wrong with my setup that combined to make it as bad as it was, my mate (Stumpy off the board) runs the swampers without any probs (we both own hilux's) but he does get a wobble but not as violent.

I still need to check my steering dampener, i run the standard j arm steering where he runs cross over so this may be a an issue too.

[Red Rover]

CASTOR, IMO. Get it checked. My MK did the exact same thing and turned out to be castor after everything else was done from swivel bearings to rotors, wheel bearings, steering box, relay box, steering dampeners etc.

[dow50r]

Caster...my 60 series did it after i lifted it too far...tried bearings, all the stuff...a pot hole would start it off, and nothing would stop it, untill you slowed down to a crawl...different tyres will be out of balance more or less, and set it off easier ....
The gearstick on the 60 would hit my knee everything moved so much

Andrew

[hokey]

Could be a toe problem. maybe your drag link is bent? if the toe is out it will start to vibrate when it gets up to a certain speed. toe is easy to check yourself aswell

[stinger]

I know the exact problem that you are describing. I used to get it on a HZJ75 Series Troopy. I spent a long time chasing the problem, changed bearing (swivel hubs & wheel bearings), check play with tie rods and all steering components. Had no end of wheel alignments and balances....

The thing that it turned out to be ...... RIMS as in the tyre rims, was running split rims at the time and all of them had some sort of buckle so it did not matter which tyre was where. Changed to new one piece sunraisers and problem disappeared.

Guess what my 80 Series has just started to do it and it is getting more frequent and these are new rims and tyres but this time I am putting it down to poor alignment and balance (has not been done for quite some time). But before I get the alignment I will change the swivel hub bearings because this sort of problems screws them up big time...

Hope this helps...

[Homer]

most probably castor wobble....mine did it too after a tyre change also (31's to 33's) while there seems no logic in how tyre dia. would affect castor ...I took the advice of a steering specialist and they added more height to my existing spring wedges and it is all good

[RAY185]

thanks heaps guys that will be tomoros job but as u say its strange it only happens on my 35s not the 36s

You said this more than a week ago. How did you go?

[DIRTY ROCK STAR]

I have had a verrrry similar shake.
SPOA.
but i have been waiting until power steering goes on before worrying too much. i was told it was steering idler box, but had it serviced and the problem was still there. hasnt been around as much lately though???
but it chewed out my front tyres really fast last time.

[chevJ40]

i replaced the rubber shackle bushes with nolathane and it seemed to have cured atleast 95% of it thanks alot for the help guys much appreciated ill let u know if i find anything else