LX570 AHC “Basics” - Added as sticky thread for AHC Issues (9 Viewers)

[TeCKis300]

Theoretically the Westcott kit shouldn’t actually provide lift. It’s more like a preload collar. The actual lift comes from adjusting the sensors. I’m at max sensor lift without any modification to the sensor arms.

But this is not a geometry thing it almost feels like something is loose but I’ve had all the bushings inspected and all the bolts double checked.

A Second off-road shop diagnosed as “I need my suspension tuned”. But obviously that’s not a real option on the AHC system. I haven’t heard others mention that jittery or loose feeling after doing Westcotts (or other spacers) and suspension sensor lift. Obviously I can’t rule it out, but at the moment the current scenario looks like air in the hydraulic line or a bad globe that isn’t properly dampening in small ripple type bumps and allows for a bit of a loose and bouncy feel.

The described symptoms are inline with @lx200inAR s comments. Given your full sensor lift, I tend to agree this is the likely issue. The nature of a 5-link with panhard lends to this loose feeling with lift.

You can somewhat rule out the underdamped theory by putting the shock in normal or sport mode. That tightens the shock orifices. If that does nothing, than it reinforces this is not a AHC hydraulic issue. A bad globe doesn't feel like the way you describe.

You need a panhard correction bracket kit.

 

[trudd]

Did your westcott set up come with any sort of lift? If you raised the rear at all you may just be feeling the affects of sagitta in the new geometry of the panhard bar.

I might've just had an a-ha moment... @lx200inAR can you look at the pics of my rear sensor brackets in this thread: My Hail Mary - need help diagnosing this shimmy / vibration

Looks like the passenger side rear height sensor is set to max height, while the rear driver is set toward the opposite direction. I want to get your take on it...

 

[eXpLoreLX]

The described symptoms are inline with @lx200inAR s comments. Given your full sensor lift, I tend to agree this is the likely issue. The nature of a 5-link with panhard lends to this loose feeling with lift.

You can somewhat rule out the underdamped theory by putting the shock in normal or sport mode. That tightens the shock orifices. If that does nothing, than it reinforces this is not a AHC hydraulic issue. A bad globe doesn't feel like the way you describe.

You need a panhard correction bracket kit.

Putting it in sport and normal versus comfort does improve the ride. But seems to make it overly stiff on slow neighborhood streets.

I’m certainly not opposed to a pan hard rod bracket. I just didn’t think it was necessary at such a limited lift. As I understand it maximum AHC lift is about 1.5 inches so pretty minimal.

And you’re suggesting a Panhard rod bracket not an adjustable Panhard rod?

(I am running 285/70r18 so a little extra lift helps me feel more comfortable running those.)

 

[TeCKis300]

Putting it in sport and normal versus comfort does improve the ride. But seems to make it overly stiff on slow neighborhood streets.

I’m certainly not opposed to a pan hard rod bracket. I just didn’t think it was necessary at such a limited lift. As I understand it maximum AHC lift is about 1.5 inches so pretty minimal.

And you’re suggesting a Panhard rod bracket not an adjustable Panhard rod?

(I am running 285/70r18 so a little extra lift helps me feel more comfortable running those.)

Actually as I read my own comment back, it's not totally correct and I'm forgetting that sport mode also tends to better control chassis motion and suppresses suspension travel. This will minimize the lateral motions due to more down angle with the panhard and sagitta. Still reinforces that this is the issue you're feeling.

1.5" seems minimal but it definitively changes things enough to feel. Which is why I'm not maxed on my rear sensor lift even with 35s.

A panhard relocation bracket s is what you need for a total fix. There's both weld on and bolt on solutions on the market now. Not an adjustable length panhard bar as that's only a partial fix.

Panhard drop bracket option?

Finally had the chance to put some mileage on the LC200 with this installed, to include freeway driving with some heavy braking. The tail wagging is significantly reduced, back to how I remember it being as stock.

forum.ih8mud.com

 

[eXpLoreLX]

Actually as I read my own comment back, it's not totally correct and I'm forgetting that sport mode also tends to better control chassis motion and suppresses suspension travel. This will minimize the lateral motions due to more down angle with the panhard and sagitta. Still reinforces that this is the issue you're feeling.

1.5" seems minimal but it definitively changes things enough to feel. Which is why I'm not maxed on my rear sensor lift even with 35s.

A panhard relocation bracket s is what you need for a total fix. There's both weld on and bolt on solutions on the market now. Not an adjustable length panhard bar as that's only a partial fix.

Panhard drop bracket option?

Finally had the chance to put some mileage on the LC200 with this installed, to include freeway driving with some heavy braking. The tail wagging is significantly reduced, back to how I remember it being as stock.

forum.ih8mud.com

Alrighty I’ll take a look since I plan on leaving the rear adjusted as high as possible (with stock brackets) probably worth a look anyway.


But I do want to clarify it’s not the wiggle and the side the side movement that I’m describing. although now that it’s been mentioned I do get that slightly side to side rocking feeling when I go around turns under load or hit G out bumps in the road. This is more like a jouncy vibration when I hit small ripple type bumps in the road the axle feels just loose. Which is why I think it’s dampening and why I initially thought it was bushings (or even loose bolts)

Although it looks like Dr. KDSS has a bracket and is a member here on the forum so I might buy one to try it out.

 

[eXpLoreLX]

Did your westcott set up come with any sort of lift? If you raised the rear at all you may just be feeling the affects of sagitta in the new geometry of the panhard bar.

Sounds like after further discussion it might be related.

I always assumed that the panhard rod geometry would cause the side to side rocking that I get and not this jouncy feeling like a loose axle.

But I’m going to try all the things available to me to get my ride quality back!

 

[nwfl4runner]

Alrighty I’ll take a look since I plan on leaving the rear adjusted as high as possible (with stock brackets) probably worth a look anyway.


But I do want to clarify it’s not the wiggle and the side the side movement that I’m describing. although now that it’s been mentioned I do get that slightly side to side rocking feeling when I go around turns under load or hit G out bumps in the road. This is more like a jouncy vibration when I hit small ripple type bumps in the road the axle feels just loose. Which is why I think it’s dampening and why I initially thought it was bushings (or even loose bolts)

Although it looks like Dr. KDSS has a bracket and is a member here on the forum so I might buy one to try it out.

Have you tried returning to stock height and testing/diagnosing?

 

[eXpLoreLX]

Have you tried returning to stock height and testing/diagnosing?

Actually that’s a very fair question. I have not because until this line of inquiry it hadn’t occurred to me that it had anything to do with my height adjustment. I guess one detail I forgot to mention is that when I had the spacers put in the shop that did the work failed to completely tighten down the panhard rod bolt and the shock bolts on the suspension. And they had backed out somewhat. When tightening everything back down I never regained my compliant ride completely. And I’ve been operating under the assumption that it has something to do with a loose suspension component or a damage suspension component, and or even a less effective globe or shock.

But I will try dialing it back down this weekend a little bit and see if it changes the behavior.

Meanwhile I went ahead and ordered the Dr KDSS panhard rod bracket so that should be here next week sometime. Along with an extra can of AHC fluid for a full flush.

 

[grinchy]

Sensor lift steals downtravel and puts the body higher. Use as little as possible. It is not a free lunch.

 

[eXpLoreLX]

Sensor lift steals downtravel and puts the body higher. Use as little as possible. It is not a free lunch.

Noted, and I may have misunderstood some of the basics in the Long Travel thread, but I thought doing the sensor lift and spacers to preload the springs (Westcott kit) put me back at ~“neutral” for travel (both up and down).

 

[lx200inAR]

Noted, and I may have misunderstood some of the basics in the Long Travel thread, but I thought doing the sensor lift and spacers to preload the springs (Westcott kit) put me back at ~“neutral” for travel (both up and down).

Probably for the front, but a preload spacer on the rear spring won’t affect your travel.

 

[nwfl4runner]

Noted, and I may have misunderstood some of the basics in the Long Travel thread, but I thought doing the sensor lift and spacers to preload the springs (Westcott kit) put me back at ~“neutral” for travel (both up and down).

one other thought, were you aligned after doing the max sensor lift? Regardless I would go back to stock height, retorque all the suspension on the ground, and then test. If everything is great, then lift as desired and panhard correction. Just remember, making your static lift permanently high essentially negates a useful “high” mode

 

[AnyMal]

Unsubscribing.

Im not going to be on regularly but anyone reading feel free to DM me for any AHC questions.

 

[LX4x4]

Would anyone be able to tell me, I understand the hydraulic fluid is being fed into the shocks from the top.

I just wanted to know once you disconnected the shock what happens to air in the system etc?
What kind of interface is used in the connection, like a flare or O ring?
Do you just top off the reservoir, maybe bleed the 4 bleeders?

Then would it besimilar to a GX or 4R where you compress the string swap in the new shock?

 

[chapba]

Would anyone be able to tell me, I understand the hydraulic fluid is being fed into the shocks from the top.

I just wanted to know once you disconnected the shock what happens to air in the system etc?
What kind of interface is used in the connection, like a flare or O ring?
Do you just top off the reservoir, maybe bleed the 4 bleeders?

Then would it besimilar to a GX or 4R where you compress the string swap in the new shock?

Thought someone with more knowledge would be able to answer but from what I’ve read and seen on a few YouTube videos is that the hydraulic pressure must be relieved via the bleeders a couple times before disconnecting the shock. Otherwise it will spray. Then reconnect a new shock, fill and bleed the system as needed via the reservoir behind the rear passenger wheel. Not sure about the gx system as I believe that’s air based and not hydraulic like the lx. Also, most of the folks here will mention that if the shock isn’t weeping or leaking then it may not be the shock system but the AHC globes being out of service life. I’m about to swap mine in soon but too busy with prescribed fire season in full swing

 

[LX4x4]

Ok, thank you, it would seem like a mandatory safety to release system pressure.

I want to understand are the globes responsible for the ride height or comfort levels, or is that in the shocks/struts. Which does what?

 

[lx200inAR]

Ok, thank you, it would seem like a mandatory safety to release system pressure.

I want to understand are the globes responsible for the ride height or comfort levels, or is that in the shocks/struts. Which does what?

We should probably back up and ask why you are disconnecting the shocks to begin with. It's pretty rare that they need replacing, although not unheard of now that some systems are getting up to 15+ years old.

Your initial question was pretty far of base from how the system works. That's probably the main reason you didn't get any responses. Hydraulic systems don't have air in them. The system has hydraulic fluid it in it and it's generally pressurized between 750-1000psi depending on load and height of the vehicle. The system is nothing like the air systems in GX/Sequioa platforms.

There are hydraulic fittings at the top of each "shock". In the LC/LX AHC system the shocks are primarily rams connected to the wheels/axles. All the shock valving and spring come from the accumulator globes and the valves actuators they are hydraulically attached to. The valve actuators and globes are mounted to the frame rails under the truck. There are coil springs as well that help the globes, but the coil springs alone cannot hold the weight of the vehicle like in a typical coil and shock suspension system. The bleeders are on the valve actuator assemblies near the globes. There are many threads with explanations of this. It would be wise to depressurize the system from the bleeders before doing any work to the shocks.


To answer your question, here's a quick tutorial on what does what (of course all of this is described in the first few posts of this thread):

Height Control: System pressure generated by AHC pump that is behind the rear passenger wheel (on USA models). More pressure means more height. The system can vary pressure/height at each corner.

Valving: Valve actuators mounted to the frame

Spring: Globes and coil springs

 

[LX4x4]

We should probably back up and ask why you are disconnecting the shocks to begin with. It's pretty rare that they need replacing, although not unheard of now that some systems are getting up to 15+ years old.

I was reading people needed replacement due to weeping, not that old, and that labor cost is high due to the hydraulic connection. So I wanted to research into it to see if this was something I could do myself if it comes to that.
But thank you for the informative post especially about the shocks being rams. To me that means replacing a weeping shock would not restore ride quality, since the valving is done else where. Weeping might lead to nuisance of fluid loss.
Another person say minor weeping is normal.

 

[tbisaacs]

I was reading people needed replacement due to weeping, not that old, and that labor cost is high due to the hydraulic connection. So I wanted to research into it to see if this was something I could do myself if it comes to that.
But thank you for the informative post especially about the shocks being rams. To me that means replacing a weeping shock would not restore ride quality, since the valving is done else where. Weeping might lead to nuisance of fluid loss.
Another person say minor weeping is normal.

You are on the right track. In terms of extra labor due to hydraulic connections—

1. bleed the accumulator until the pressure discharges and corner drops
2. unscrew the 1 fitting at the top of the shock
3. there is no step 3

Now you do of course have to do the reverse, including bleeding. But it's not significantly more work because of the fitting. The care comes in the bleeding after.

 

[KarlHungus]

Getting 120K mi service on my '13 this week - not sure if AHC fluid ever changed - is $225 good price for AHC flush?