KDSS Conundrum (1 Viewer)

[Goldbug]

I have a 2011 LC and did a Dobinsons suspension lift about a month ago. I did the requisite steps with loosening and then tightening the KDSS at the time. What I didn’t fully appreciate at the time is that my garage isn’t level due to a floor drain.

I noticed the truck wasn’t level a few days after the lift and have tried multiple times to correct it since, but it’s keeps going back to 1-2” higher on the passenger side.

Should I try to significantly over correct? I’ve been getting it to even. Or do I need to go to the dealer?

Thanks, kinda bummed that I didn’t quite pull off the self install lift.

 

[2021 LC200]

Take this with a grain of salt as I am not a KDSS expert by any means, just sharing my experience;

On my suspension wise stock 200, I rotated the other day the spare into the mix. During the process I took a break to eat something. I had not done the two turns on the KDSS bolts, never came to my mind to do so. Once i was done i noticed a slight tilt.

I then decided to do the 2 turns and shook/rolled the vehicle on the running boards a bit and let it sit for a while. It then came back to level and I closed the KDSS bolts again. Been level since.

It therefore seems to me:
- KDSS will slowly leak fluid from one part of the circuit to another part with the bolts in the turned in/regular position
- In order to get level the suspension and springs need to be balance/keep the vehicle level with the KDSS bolts turned out (i.e. KDSS not forcing the car)

In your case you may just need to park on a level part of the drive way or road, then undo the bolts 2 turns, perhaps shake/role it a bit and let it sit for say 15 min. Then close the bolts and see what you get.

Hope this makes sense. I may also be wrong in the understanding of the KDSS. Just seems so in the way it responded in my case.

Keep us posted as you figure this out.

Good luck!

 

[bloc]

Generally when people have level issues on a vehicle after a lift the best advice is to make certain you have the rear springs in the correct spot. Due to poor instructions and differences in driving position between australia and here, ARB (and I'm sure other companies) have led to a lot of confusion with these springs. If they definitely are in the correct spots, then yes a floor drain or non-level surface during KDSS lock-in can induce a lean. I've left my home and done this in a large parking lot when I didn't have access to a flat-enough driveway.

But 2021 is correct above.. there is an ability for pressure differences in the two circuits to stabilize, and if frequently parking in a spot with articulated suspension you can end up with a long-term lean that won't seem to go away.

Why this wouldn't have happened in the same parking space before a lift? I wonder if the lift changes some of the geometry of the KDSS system making pressure imbalances more likely to translate to a lean.. total hunch.

 

[linuxgod]

First question is how much lean exactly? Measure from the top of the wheel or center of the wheel hub (your choice but I prefer the former) to the lip of the fender.

KDSS lean isn't really a thing unless your valve is having issues allowing fluid transfer between the chambers. Any lean should equalize after some time. Even if you closed the valves with the truck leaning, it should level itself after a day or two of sitting somewhere level. One thing you might try is to back into your garage for a few days and then see if the lean corrects (or overcorrects). If the lean is still there after doing so, then it's an issue with spring heights. If the lean changes, report the new measurements along with the current ones and let's debug it together.

If the lean doesn't change after parking backwards, I'd do like @bloc says and make sure the springs are in the right position. If you're 1.5" too high on the passenger's side and that's the taller spring, have the shop swap positions. If after the change you're much closer, you can use OME trim packers (spacers) on the lower side rear spring to fine tune the height to get you within the +/-15mm target that Toyota considers normal.

 

[skrypj]

If you are getting a significant amount of lean when opening the valves on a flat floor then you may need open the valves, put some pieces of wood under the appropriate tires, then close the valves, then drive off the wood.

Its kind of hard to do on a flat floor because it you put both pieces of wood on one side of the truck then the whole truck just leans. I have seen were people have done it on a lift where they will jack up the appropriate tire with a floor jack while the truck is level on a lift, then close the valve. when I would do it on my GX I would put the pieces of wood on the higher side of the truck, then use my hydraulic jack stands to lift the opposite side of the truck from the frame until it was sitting level with the wood under the other tires. Then I would close the valves.

That said, on my GX460, I feel like I had to readjust every few months anyways. I would get it nice and level and then it would eventually work its way back. In the case of my GX I was running Bilstein 6112's in the front and the Eibach Load leveling springs with adjustable height collars in the rear.

 

[Goldbug]

Thanks guys. I've been trying to correct it by jacking up with a floor jack with valves open, get it to level, then close the valves. Which I think is what @skrypj is talking about.

@linuxgod I'll take pics of the measurements when I get home and check out the springs. I think I installed them right, but it was a bear of an install, so I'll take another gander. The floor drain is in the middle, so I can switch bays between the 40 and 200 when as soon as I put the steering back in the 40.

 

[skrypj]

Thanks guys. I've been trying to correct it by jacking up with a floor jack with valves open, get it to level, then close the valves. Which I think is what @skrypj is talking about.

@linuxgod I'll take pics of the measurements when I get home and check out the springs. I think I installed them right, but it was a bear of an install, so I'll take another gander. The floor drain is in the middle, so I can switch bays between the 40 and 200 when as soon as I put the steering back in the 40.

Its more than that though. You have to move it to beyond level in the direction opposite of where it is naturally leaning. so if its an inch low on the drives side sitting on flat ground, when you open the valves, set it so its leaning an inch right. Then close them.

I never found that it did anything if i opened and closed the valves with it sitting perfectly level. It would just go right back to leaning.

 

[Goldbug]

Its more than that though. You have to move it to beyond level in the direction opposite of where it is naturally leaning. so if its an inch low on the drives side sitting on flat ground, when you open the valves, set it so its leaning an inch right. Then close them.

Yes, I think you're right. I'm going to take an early train home now actually so I can go do this. hah!

 

[linuxgod]

Thanks guys. I've been trying to correct it by jacking up with a floor jack with valves open, get it to level, then close the valves. Which I think is what @skrypj is talking about.

@linuxgod I'll take pics of the measurements when I get home and check out the springs. I think I installed them right, but it was a bear of an install, so I'll take another gander. The floor drain is in the middle, so I can switch bays between the 40 and 200 when as soon as I put the steering back in the 40.

The driver's side spring should be pretty easy to get in and out but yes the passenger's side is a PITFA. I've tried all sorts of tricks disconnecting the sway bar, panhard rod, KDSS end link, etc and it always sucks to get it back together.

 

[daneo]

I don’t have numbers to back this up, but despite the videos on YouTube using the valves to level out a side-to-side lean, most people find that the lean will come back over time. It seems to be a red herring in my experience and others. Bloc has a good breakdown of the KDSS circuit that shows that the system is valved to eventually revert back to homeostasis after an external imbalance is introduced.

Again, no numbers to back this up, but it seems the majority of people find success by compensating in coil length or trim packers.

 

[bloc]

Not just a red herring.. it’s literally using the KDSS hydraulics and sway bars to fight a lean caused by something else.

The block “trick” is absolutely not the right way to make this right, as long as the rest of the KDSS system is healthy.

 

[2021 LC200]

Not just a red herring.. it’s literally using the KDSS hydraulics and sway bars to fight a lean caused by something else.

The block “trick” is absolutely not the right way to make this right, as long as the rest of the KDSS system is healthy.

I see the same.

step 1 - Put the vehicle on a horizontal surface and open the KDSS bolts. If it levels then close up and you are done.
if not step 2 - Look into why the suspension is not level with the KDSS open. The issue then per bloc is most likely in unequal springs and after swapping, potentially apply a thin spacer to do the rest

 

[Goldbug]

Well, it measured 37” on pass side and 38” on driver. Back was only off by 1/2 inch. So I opened the valves, lifted drivers side and closed them. At first just got to 38” on both sides. But that’s what I did before. So lifted until I got to 38.5 on drivers side and 37.5 on passenger. Gonna take it for a ride and see if it levels out or goes back to passenger higher.


Pics before adjusting:

 

[Goldbug]

Well, after 15 mins of driving (admittedly not enough) the drivers side is now 1/2 inch above passenger. Originally, passenger had been 1” higher. So progress!

I’ll park it in the driveway from now on and see if it levels out or goes back to high passenger.

If it does, then I think I take the wheels off and inspect my suspension work.

 

[skrypj]

Not just a red herring.. it’s literally using the KDSS hydraulics and sway bars to fight a lean caused by something else.

The block “trick” is absolutely not the right way to make this right, as long as the rest of the KDSS system is healthy.

And yet this only seems to be an issue on Toyota's with KDSS from what I can tell. I dont see 900 threads on other truck forums with lean issues.

 

[2021 LC200]

From what I know of the system:

- KDSS will maintain pressure and the stabilizers working, when one side rear and front wheel are depressed during cornering.

- It allows free movement on diagonal wheels for articulation on undulating terrain.

- It does not fix long term lean caused by suspension/spring imbalance.

- Also it will hold on a lean when the vehicle is parked like that for longer periods by fluid equalizing in the two parts of the circuit. This should resolve itself when you drive.

Overall remains an excellent system without electrical sensors or actuators. It by design does not resolve after market spring imbalance issues. That requires different parts, shims etc.

This maybe a bit basic, but there is not much more to it. Not hard to imagine fluid leaking from one side to the other when there is a constant lean per the upper diagram/condition.

Control cylinders are on one side, connected to the stabilizer bars taking care of either side.

 

[bloc]

And yet this only seems to be an issue on Toyota's with KDSS from what I can tell. I dont see 900 threads on other truck forums with lean issues.

I have owned five Toyota 4x4s and the only one that didn’t lean had leaf springs and torsion bars.

Other platforms don’t have a black box to distract people from the real cause. A KDSS system that has failed hydraulically can have a sudden lean, but so far I haven’t read about one of those that didn’t involve severe corrosion or obvious mechanic error.

 

[bloc]

If anyone wonders what the mechanicals look like, I dissected one of those corrosion failed valves and documented all of it.

Anatomy of a KDSS valve

I think you guys and gals are gonna like this.. HUGE thanks to @jimoldguy who shipped me his rust-damaged KDSS valve after it was replaced for him with a new one. That can't have been cheap. Fortunately for me he kept the old one, and when I PM'd asking if he'd send it for a project I'm working...

forum.ih8mud.com

 

[2021 LC200]

And yet this only seems to be an issue on Toyota's with KDSS from what I can tell. I dont see 900 threads on other truck forums with lean issues.

Is it only a Toyota KDSS issue...? Or is lean caused by aftermarket mods? And other vehicles with more complex systems just fail on their own?

 

[bloc]

Or is lean caused by aftermarket mods?

Mine leaned when dead stock with 100k miles, and it did so until I put new springs under it. Zero changes to the KDSS system other than balancing.

In the manual they are allowed to lean by a surprising amount, though I can’t recall the number at the moment.