Keep us posted! KDSS was/is a concern of mine at EOL. Unlike XREAS, there is no off the shelf "down grade" replacement that I'm aware of. So in short I too wonder what fixed end links will be like. Your are brave!
KDSS Long term reliability?
- Thread starter Vizguy
- Start date
Keep us posted! KDSS was/is a concern of mine at EOL. Unlike XREAS, there is no off the shelf "down grade" replacement that I'm aware of. So in short I too wonder what fixed end links will be like. Your are brave!
Great news! Any lean?
I’ve got your switch and it makes a nice difference for those situations where there is rough road, but I still want to drive above 12 mph. Nice work Dom!
I just had my front KDSS piston replaced a week before the bumper to bumper warranty ran out. Discovered it 2.5 months before the end of the warranty while swapping my winter wheels on. I had to wait a month and a half for the Toyota dealer to get the special service tool in to bleed the system after replacing the shock.
Before:
and After:
Before:
and After:
Someone with more knowledge feel free to correct me but from what I understand, no. The swaybar mounts on the frame required are not present on a KDSS 4Runner.
Yes 100% you can. I’ve help about 2-3 guys do it. Only thing is you will need to get some tabs welded on the frame for rear sway bar. In my world that is really easy to do. The rest of it is all there already.
Sent from my iPhone using Tapatalk
johnsky1975
New member
A fluid pressure equilibrium in both chambers (up and down) will result in the cylinder wanting to extend and therefore applying a force to the sway bar. Same front and rear. The reason for this is that the cylinder is a single ended cylinder rather than a double ended one. By that I mean that it only extends the shaft in one direction. The result of that is that the internal area where hydraulic force is applied is greater on the top side of the cylinder than it is on the bottom side of the cylinder. The difference in area where force is applied is equal to the cross section area of the shaft. KDSS cylinders have relatively large shaft diameter compared to overall internal cylinder diameter.
So - as a result of having more area with applied force on one side - if the pressures in the system are balanced, the cylinder will try to extend. This is the same reason that all gas charged shock absorbers always seek to extend. If your shocks had a 20mm diameter shaft and 400psi - they'd push with about the same force as KDSS when balanced in pressure top/bottom.
If it were a free cylinder with nothing stopping it - it would extend until the force on both sides balance (but the pressures would not be balanced). In this case the cylinders extend until the additional force trying to extend them is balanced by the force resisting extension. That force is gravity pushing down on vehicle body and the sway bar force up against the cylinder. So the result is that it pushes the body up with a force of about 200-300lbs. And it creates a lean in the same way that a spring with 200lb of force would do on that side.
What is happening when you compress one cylinder all the way closed (rear by jacking), and presumably keep the front somewhat compressed, is that you're effectively increasing the oil volume in the lower chamber and decreasing the volume of the upper chamber as a net effect. Then you balance the pressure. When it settles back after closing the chambers, the upper chamber ends up with a lower pressure (because you've moved some of the oil from the upper chamber to the lower chamber). Then the system can reach an equilibrium of force that applies less "push" on each cylinder to cause the lean.
The reason it probably goes back to a lean after a short time is that the system likely bleeds pressure between chambers anyway. Either around one of the cylinder pistons, or possibly by not having the shutter valves tight enough. Either way - over time at the pressures run in the KDSS system (often exceeding 1,000psi), it will likely return to its original state of lean.
The best long term fix is with springs to offset the force of KDSS. IN a perfect world, Toyota would use double ended hydraulic cylinders and the balance would always remain neutral. That's what McLaren does with its KDSS sysetm. - Not sure if you know, but Mclaren uses KDSS in its supercars, but it uses a double ended ram with neutral force on all 4 corners.
Toyota also uses an even more complex system in the LX570
(I think earlier I said single acting - it's double acting, but single ended)
I Know this post is quite old by now, but I thought I'd try getting some feedback. I have a 2007 GX470 with KDSS. I've never gotten any KDSS trouble codes. I've been dealing with an intermittent lean to the passenger side since I lifted the vehicle a couple inches. I performed a rebalancing about a year ago that seemed to last for many months. Though the vehicle would still roll more to the passenger side when negotiating curves. It would roll very little to the driver side. After a recent trip the driver side seems to have lifted again. The rear cylinder seems to be pushing down against the sway bar harder, and requires more force to compress with a jack than it used to. I tried the rebalancing procedure a couple times to no effect. I have a couple questions. The KDSS system in general seems to behave in paradoxical ways. I'd think, if anything, a KDSS vehicle should lean to the driver's side when it's lifted? It seems like the front and rear pistons shouldn't both be able to move downwards in the cylinders as both cylinders are pulled upwards due to the frame that they're attached to being raised upwards by lift springs. It seems like this should cause the driver side of the vehicle to resist upward movement, causing a lean to the driver's side? My second question is this. I'm wondering about the feasibility of relieving some pressure in the upper circuit by compressing the rear cylinder and cracking the bleeder fitting briefly, potentially allowing the piston to move further upwards, thereby allowing the vehicle to settle a bit lower on the driver side? I realize this would reduce the overall fluid volume and pressure in the system, and could reduce the on road performance, but thought it might be worthwhile if it brings the vehicle more level. Any thoughts would be appreciated.
