Swaying On Highway

[Jay11]

Hey guys,

Need some help!

My 34 GTT has started swaying on the highway when I hit minor bumps.

The best way to describe it is that it feels like the back wants to go a different way than the front.

Also it feels like it kind of corrects itself a bit, not sure whether that's got something to do with the HICAS?

All I know is it scares the hell out of me driving on the highway now, it's kind of like driving on ice (not the drug).

Any help would be great!

Cheers,

Jaylon

[chiksluvit]

might be too much toe in

try wheel alignment first, see how much toe in at the rear the car has

doubt it's the HICAS rack, though still possible, but get rid of HICAS anyway

[Jay11]

True, I forgot to mention I got an alignment done on Monday and I had the front castor bushes replaced.

But the issue was happening before that, thought it would fix it but it hasn't.

[Bunta]

I had this when i had one screwed rear shock, after every bump it felt like the car 'wiggled' around before settling down

[jrm]

If your HICAS steering sensor is mis-aligned, this can cause 'crabbing' at speeds 80kph - worse, at approximately 110kph HICAS will turn off which will stop that crabbing and the rear end would kick out (experienced this myself).

I would suggest you get a suspension specialist to check your rear suspension first - see if there's any movement in bushes, etc - and particularly in the HICAS rear steering rack - this can and does happen, as it's a wearing part. If the HICAS steering rack is worn & has movement, it will basically like your rear wheels are loose and that can make the car particularly unsettled even at 60kph going over bumps (I've experienced this too).

Anyway, give that a shot first and see if you can rule things out - but there's plenty of things you can do once you've ruled that out.

[eiresgaus]

Had this happening to my car a few weeks back, bushes were wrecked and my shocks weren't in a good state.. Changed everything and its not doing it at all anymore.

[Jay11]

Thanks for the replies,

I'm taking the car in on Monday to get it checked.

I think it might be the shocks or bushes.

The HICAS is probably just correcting the car when the back kicks out a bit?

[Jay11]

Got the car checked out today,

looks like it is the HICAS.

I'm gonna just buy one of them lock out kits to fix it.

[Jay11]

Got the HICAS lock bar installed and the car is worse than before, now happening bad at 80k's when going over a bumpy surface, can even do it at 60k's.

When my car was parked in my driveway I tried to push the rear from side to side but it had no give, it was solid as a rock.

Not sure if it's going to be a rear shock or maybe bushes?

It got aligned on Monday, thought they would pick something like that up when they were aligning it?

Trying to sell the car so gotta get it fixed ASAP.

Anyone have any advice?

[KiwiRS4T]

What is the castor figure? Sounds like it started after they changed the bushes. You need max castor for straight line stability at speed 6deg or 7 deg. (usually only acheivable with adjustable arms although you can usually get a bit of adjustment with eccentric bushes). But from what you say it could be something coming adrift. Suspension shop should have checked all bolts for tightness and used a bar to check ball joints etc. A suspension shop should have a rig to test shocks or you can do it yourself. Walk around the car and push each corner down hard and let go. It should come up and stop. If it goes up and down even once the shock is shot. What is your warrant of fitness test like over there? In NZ the inspection usually picks up faulty ssupension items and a new wof will be good if you are selling.

[Jay11]

Took it back in and they aligned it all again and tightened a control arm?

Issue is fixed she's running perfect now