HELP, can't diagnose LX 570 front end problem (8 Viewers)

[TexomaPowerboater]

I've done a ton of work on this car( 2011 LX 570 with $177K miles), like $20K worth and after last repair it now so bad I can't drive it. When I'm on the highway in normal or comfort mode and I hit any kind of a bump really the car will bump steer/shake back and forth uncontrollably. It's like something is going on in the front end that is causing it to dart side to side several times before it will settle down and it's so bad now it really doesn't settle down at all any more it just keeps shaking side to side. It's not noticeable at all at lower speeds 40-50, but once I'm at 55-60+ it is so bad the car can't be driven, at 80mph it's dangerous enough to cause a wreck. I'm afraid something going to let loose and end up wrecking the car. It seems to disappear completely when I put it in sport mode. It's worst in comfort mode. Neutral mode is not as bad, but still bad enough I don't want to drive it.

I had been trying to chase down a "wobble" where when I hit a bump at speed on highway the car would kind of rock side to side just briefley, maybe one rock side to side and done. I've had a ton of work done basically all new stock suspension - new front and rear shocks and springs, new front lower control arms, new rear lower and upper control arms, new front and rear sway bar bushings, new steering stabilizers, new accumulator globes, AHC fluid flushed and fresh fluid done. Only thing I haven't done is front upper control arms because they keep saying they are fine and I've had 3 people look at it. All work done within 3K miles.

I've had car in and out of shop about 4 times now. The last time I took it and we did front and rear sway bar bushings, new rear lower and upper control arms right and left. Right after that work was done I took it home got on highway noticed the problem was now 3-4 times as bad so I took it back to shop and told them to figure it out - that maybe it was alignment or tie-rods, so they looked at alignment again and they don't see any slop in tie rods. They are stumped as to why the problem would exist in normal or comfort mode, but not in sport mode. PLEASE HELP! I've got like $40K into this car now that I got for road trips and my daughter to drive, but can't be used.

 

[tbisaacs]

I would stop throwing parts at it until you get a clear diagnosis.

Have you looked at rear panhard bar? For a live axle truck it’s normal to have some jostling but if bushings are worn it will get worse.

You mentioned front sway bar bushings but not links. The links have a ball on the end that tend to degrade, rust, and seize. At that point they stop doing their job.

How is your alignment? Too much toe or caster will cause darting behavior as well.

 

[bloc]

@TeCKis300 does sport mode only alter damping or does that change spring rates as well?

 

[TeCKis300]

@TeCKis300 does sport mode only alter damping or does that change spring rates as well?

Primarily damping. It may change the sensitivity to engaging the front secondary high spring rate.

To the OP, this is troubling as I would expect based on the symptoms, that it is due to the globes. I still think it's the globes in some manner because it sounds like it's a compliance issue. Does the symptom only really show up when hitting a large/sharp bump?

It may be a deeper issue like the No.2 Gas Chamber along with the damping force actuator. Possible the fluid got contaminated and it's plugging some orifice?

 

[TexomaPowerboater]

It shows up when hitting any bump small or large and seemingly any compression at all on the front and it will start to rocking. When I had globes done it improved the ride across the board and after that work it didn't fix the problem, but it was a manageable problem - just a brief side to side rock when I hit a somewhat larger than average bump in the road. Now after the sway bar bushing front and rear, plus the rear upper and lower control arms, it is unmanageable constant wobbling back in forth and much more violent. Why would it be the globes if I've replaced those already and it improved ride and didn't escalate the problem like it did when I had all the work on the rear control arms done.

I thought it was tie rods but they are saying there is no slop there so maybe I need to look at the rear more. I've driven driven trucks all my life as my daily driver and I've never once felt the truck have a side to side wobble like this so I don't understand the straight axle comment.

Thank you so much for all the comments even if I don't understand them all I very much appreciate them.

 

[tbisaacs]

I've driven driven trucks all my life as my daily driver and I've never once felt the truck have a side to side wobble like this so I don't understand the straight axle comment.

Panhard bar on the rear axle is attached to opposite side of the frame. As the axle travels it moves side to side.

There is some normal side to side wobble that is caused by this. If the bushings are worn out it will get exaggerated. If you have a dampening problem, that would also exaggerate the wobble.

 

[TeCKis300]

It shows up when hitting any bump small or large and seemingly any compression at all on the front and it will start to rocking. When I had globes done it improved the ride across the board and after that work it didn't fix the problem, but it was a manageable problem - just a brief side to side rock when I hit a somewhat larger than average bump in the road. Now after the sway bar bushing front and rear, plus the rear upper and lower control arms, it is unmanageable constant wobbling back in forth and much more violent. Why would it be the globes if I've replaced those already and it improved ride and didn't escalate the problem like it did when I had all the work on the rear control arms done.

I thought it was tie rods but they are saying there is no slop there so maybe I need to look at the rear more. I've driven driven trucks all my life as my daily driver and I've never once felt the truck have a side to side wobble like this so I don't understand the straight axle comment.

Thank you so much for all the comments even if I don't understand them all I very much appreciate them.

Do you have any mods at all?

With all the parts changed, you should be good. It's wholly possibly a new globe failed too?

I wonder if they torqued the control arms with the vehicle weight on the arms, with bushings in the neutral position. But I don't think that would result in the degree of problem you're experiencing. It's definitely a compliance issue in some manner.

 

[sedole]

I'm with @tbisaacs here. I'd look at the panhard bar. Check bushings for wear and check bolts for proper tightness and maybe brackets for damage. There's been a couple others that have complained of similar issues that turned out to be the panhard being loose.

 

[bloc]

I know we haven't seen one of these confirmed yet, but thoughts on the possibility of one of the relief gas chambers in the above diagram failing?

I believe they use the stainless steel bellows construction like in the KDSS accumulators so should be much more durable than the rubber diaphragm in the globes, but one side having significantly different spring rate than another could do all kinds of weird things.

But yes, panhard should definitely be looked at. Especially if things got worse after work on the rear axle.