GU Shimmy Questions

[BOB_1]

Okay- I have read lots about the dreaded Nissan Shimmy.
First off a brief description (if you havn't read the other 25 posts about this).
99 GU Wagon - Not much lift- maybe 1-2 inches
Brand new 285/75/16 Xterrains on standard steel 16x8s
I did it a bit on the old 265 MTRs but not as bad
Newish Toughdog RTC steering dampner (without the spring- it makes it worse I reckon)

When speeding up starts vibrating badly about 80 kays, but backing off it takes to about 65 to get rid of it. Does it to about 90-95 or so.
It doesn't seem to happen really bad until you hit a little bump which sets it off.
Wheel bearings are fine. Tyres have been swapped front to back to see if it was badly balanced tyres. Directional so cant be swapped side to side.

There is a little bit of slack in the steering box- not much though - can this be adjusted and how? - Could this be a cause.

Tie rod ends seem fine- no slack in them.

How do I check the panard bushes. They are a bit of a pain to get the bolts undone- but I will this week with a rattle gun - but with a big screw driver you can move the car of the the rod end one around in the bush. Could this be part of it. Should the bush be fairly solid.

How do I check the radius arm bushes ( i guess these are the trailing arm bushes,)

Any help would be great- its a pain looking for my fillings on the floor while driving

[InSanE]

check your kingpin bearins in the top and the bottom of the knuckle try removing the 4x 14mm bolts pop out the top one and remove the shim in there i find this helps them a bit

[BOB_1]

So the shim isnt needed- ill get my manual and have a look, I sort of know what your talking about though,

[InSanE]

nope the shim isnt needed i have like 20 of them in my toolbox at work when i was at nissan we used to remove them to stop shimmy problems

[BOB_1]

Thanks, ill give it a try, what about the panhard rod, how soft is the bush? Should I be able to move the rod with a screw driver?

[InSanE]

yea it should have some small movement but if you doubt it just take it off and inspect the bushes its only a few bolts

[BOB_1]

Thanks again

[AndrewPatrol]

Surely taking the shims out risks setting the preload at too high a level and chewing the bearings out. Exactly why I dont take my car too Nissan anymore. Sure doing it properley is abit of a pain but who's car is it?? Its not a Nissan mechanics.

[BOB_1]

So do you have any idea what it is?
It seems that there is no real solution, some say tyre balance, some say wheels, some say mud in wheels, some say bushes, some say radius arm angles, some say panhard rod bushes or angle, some say shims, some say kingpin bearings, some say wheel bearings, some just say farken nissan shite bent chassis from factory,

Any good solutions that will enable me to safely do 80kms an hour will be helpful instead of just criticizing somebody elses constructive ideas without adding why this is not going to solve the problem.

Thanks for your help - InSanE, If it fixes it good, if it doesn't ill just put them back in. Cheap and easy first

[fatassgq]

Before you go taking shims out that where there when the vehicle was new and therefore are not the reason you now have the shakes....

Check panhard bushes thouroughly. Your next step is to check you radius arm bushes (leading arms) mainly at the diff end. there are four bushes that can easily be your culprit.

These are generally the main causes.

Other thing that you have not specified is if they are factory bushes or nolethane/urethane aftermarket bushes. If the truck is lifted then there is a chance that whoever lifted it used urethane offset castor correction bushes.
Which don't last real long could be causing a problem.

Also if you suspension has sagged and you have castor bushes in you may have too much castor which is another major no no.

Once again don't pull shims out. They where there when the truck was new and Nissan would not sell many of em if they had the shimmy from factory

cheers
Brian

[gu4800]

Not trying to dismiss the issue, but I always thought it was just a "fact of life", even with only a slightly lifted Patrol.

My car had 35,000 klm's on it when I lifted it, and it had the "shakes" from the moment I did the lift. Not enough to annoy the piss out of me, but certainly there. Also, not all the time. So given the low klm's, I didn;t really think it could be bushes, etc so early.

Given that so many people have many different answers (as you said above - some say bushes, castor correction, shims, etc, etc ,etc) I just put it down to being a "fact of life".

[BOB_1]

Yeah - the shims from factory suggestion is probably right- only thing is I have made the tyres much bigger than factory so have made the problem - which did already happen with the smaller tyres worse by putting bigger tyres on. ( I have no plans of going back to small tyres though). The car has factory bushes all through the car, with as I said a minor lift if any - from an OME telstra kit.

I am fairly remote where I live, is there a way to measure caster using basic tools and some maths.

I am going away in a fortnight and would like to have it a bit better by then but I want to be right with any parts I have to order because I have to get them couriered or mailed to me. Might have to start pulling it apart and playing with it after work tonight.

Its good to get some constructive thoughts instead of people just ripping into each other with no justification.

Thanks

[BOB_1]

Okay tonight I checked the panhard bushes- like new, so took the shims out of the king pins to see if it made any difference, got rid of most of the wobble, why and how does this do it and (it seem it might from above) will it cause long term damage with these out. Luckily they only take ten minutes a side to get out.
I also remember a post a while ago about a spacer that is put on the vehicle end of the radius arm that fixes it, can anybody put there finger on that post, or details,

[Tiny]

check your wheel bearings

[Vulcanised]

i was "warned" about the Patrol shakes before i got mine..... didn't have it driving home with 2" of lift on 31" tyres....... put the 35's on it and 4" of lift and it gets so bad at 110kph my vision starts to blur It got worse after i ben the drag link...... thats being replaced tomorrow..... castor plates when they arrive will allegedly help the problem.... and adjusting the diffs back into centre with adjustable panhards is supposed to help as well. My shimmy starts at about 60kph.... dissapears at about 80, and comes back in force at around 95kph. Same thing too... a small bump sets it off and it keeps on keeping on until you slow down enough to stop it.

[fatassgq]

Roedao....Don't put castor plates on your truck with only a four inch lift and 35" tyres it will give you too much castor.

Use drop boxes and it will drive soooo much better.

I would use castor bushes in your case over castor plates if you cant afford or want drp boxes.

As far as the original post goes.

BOB_1 can you do me a favour and measure your front bumpstops for me? Make sure they are not broken at all and just measure inside the coil from the bottom of the rubber bumpstop to the raised steel hat that the coil locates on at the bottom.
Post up this measurement and I may be able to help more.

cheers
Brian

[BOB_1]

Fatassgq -
45mm between bump stop and top of spring cone both sides when sitting flat. Which isn't much really. Also I have a high mount on the front and steel bullbar and dual batteries.

[InSanE]

told you it would help buddy i would reccomend replacing the kingpin bearings sometime in the near future to, its a weakness on the GU's

[fatassgq]

Front bumpstop height for a gu is normally about 55-60mm give or take for a standard truck so you are lower than that.

You probably now have too much castor as the 285's are a bigger tyre.
As you said it was not as bad with the 265's

The bigger the tyre the less castor you need to do the same job (get the truck to ride nice)

Maybe a set of 30mm coil spacers would fix up the prob.
Definitely still check your radius arms thouroughly. I don't care how new the truck is.

[BOB_1]

Thanks for everybodys help- hopefully it will help others with the same problem one day.
I might order a bigger set of springs, I wanted new ones anyway, My Mav had a 4 inch kit in it and although it did get the shakes sometimes it had really soft springs and drove really well for a half assed suspension setup.

I had a look at the radius arm bushes, how stuffed do they have to be to make a difference, they are ones with holes in them (factory I guess, my mav had solid ones I remember when I put the caster bushes in) and there are a couple of little tears from the holes. I guess you are talking the front radius arm bushes where the arms bolt to the diff housing?

Might get a set and chuck them in- actually I might have a set at home in Melbourne left over from the Mav.

Thanks again

[BOB_1]

Sorry- how chewed out would the radius arm bushes look if they were stuffed, they have a couple of small tears from the holes in them.

[junr]

Hi Bob- radius arm bushes generally flog out around the centre steel sleeve- they will look "cracked" or torn there, like that sleeve (that the bolt goes through) is gunna tear away completely. Check these with a torch or lead light- PS: new from Nissan at trade price just under $200 for all four! Ouch.
I had exactly the same problem- improved 50% with new radius arm bushes (old ones flogged out on 3 year old GU!). But also had 4way RTC like you- I am not bagging 4way, cause I luuuuurv my Tough dog setup, but these RTC steering dampners are total SHITE! With the spring off or on, the things are NOT dampning your steering- take it off and try compressing- now do same with even Nissan original- even original has stiffer dampning. I replaced with a Ridepro dampner from ProComp (could use OME from ARB also) and HAPPY HAPPY DAYS!!!- no shimmy here chopper, here no shimmy!!!!!!!!!!!!!!!!!!!!!!!!!!!! :-) :-) :-)

[junr]

PS: Not saying that these things are definately going to solve your problem, I know how frustrating it is when people come up with so many answers when all you want is THE solution! But it is a process of elimination. You really gotta check ya castor etc and as fatassgq mentioned, drop boxes are the go- even if only to improve the way your front end will ride up and over obstacles (they flatten your radius arm angles back to standard instead of just rotating the diff). PPS: I'd stay well clear of pulling shims outa my diff ends.

[junr]

Hi Bob- radius arm bushes generally flog out around the centre steel sleeve- they will look "cracked" or torn there, like that sleeve (that the bolt goes through) is gunna tear away completely. Check these with a torch or lead light- PS: new from Nissan at trade price just under $200 for all four! Ouch.
I had exactly the same problem- improved 50% with new radius arm bushes (old ones flogged out on 3 year old GU!). But also had 4way RTC like you- I am not bagging 4way, cause I luuuuurv my Tough dog setup, but these RTC steering dampners are total SHITE! With the spring off or on, the things are NOT dampning your steering- take it off and try compressing- now do same with even Nissan original- even original has stiffer dampning. I replaced with a Ridepro dampner from ProComp (could use OME from ARB also) and HAPPY HAPPY DAYS!!!- no shimmy here chopper, here no shimmy!!!!!!!!!!!!!!!!!!!!!!!!!!!! :-) :-) :-)

[BOB_1]

Thanks for the info, Radius arm bushes are on the agenda to be changed next week when im on leave, Will probably do king pin bearings and ill have a look around at home for my old GQ 3inch springs I had lying around somewhere. Drop boxes won't help at the moment, my GU is lower than standard at the front .
Hopefully this will sort some of it out. My girlfriend is driving it at the moment and I have her VX commo - not a bad swap considering the vibrations

[AndrewPatrol]

Bob, surely even you can see that removing the shims is a band aid solution ( which Nissan surely wouldnt fit just for the hell of it )
Surely you would like to do the job properley and check the bearing preload and set with the correct size shims.
Yeh sure I'm criticizing other peoples responses 'cos I believe there is good reason, its butcher mechanics.
You said yourself that no-one can give a correct answer to the persistent problem and then you go on about your bushes showing signs of wear, Surely thats a good place to start. Why dont you do a search - theres reams of stuff been written about this

End of rant ( BTW this is in response to your response further up. )

[AndrewPatrol]

Bob, surely even you can see that removing the shims is a band aid solution ( which Nissan surely wouldnt fit just for the hell of it )
Surely you would like to do the job properley and check the bearing preload and set with the correct size shims.
Yeh sure I'm criticizing other peoples responses 'cos I believe there is good reason, its butcher mechanics.
You said yourself that no-one can give a correct answer to the persistent problem and then you go on about your bushes showing signs of wear, Surely thats a good place to start. Why dont you do a search - theres reams of stuff been written about this

End of rant ( BTW this is in response to your response further up. )

[BOB_1]

I think this post has more info in it than the other 50 posts about the Patrol wobble, It actually goes through most if not all of the reasons why they do it in one post. I thought I would see if anybody knew what caused the wobble I have - compared to the wobble of somebody with a 6 inch lift, and 44 boggers, and no bushes.

From this post I have found - My king pin bearing probably need changing, I pulled the shims as stated above to see if that was the problem, now I know it is, ill change them as stated above.

My Front radius arms are rooted, and the back ones are probably on thier way out and I have gone through the list above finding most other things are OK. Things will be changed as time allows.

Thanks to the people that had something helpful to say, you helped me and probably will help others in the future

[BOB_1]

I have done a lot of work removing the shimmy now, Replaced radius arm bushes, steering stabiliser, checked other bushes and played with the front suspension.

Anyway, Today, I swapped wheels and tyres with a mate with a new GU. The wobble swapped cars

He wasn't keen to leave the tyres the other way around so at least I have narrowed it down to a wheel/tyre problem.

Most likely dodgy rims as when they were balanced with the new tyres on them a few weeks ago they balanced up fine,

So monday Im off to buy a new set of wheels - Thanks everybody for your help.

[John Davidson]

Has anyone had any experience fitting the "Drop boxes" to the back of the Raduis arms? Did they help with shimmy problem?