Updating AHC system

[maxse01]

This is wonderful info, thank you for sharing. My 05 just kicked over 112k and the system is working great. All I have done is some fluid flushes and new fluid. It's light duty for now, no towing or heavy interior loads. I expect the system to keep lasting for a while longer. I'm glad to know that I can go with a heavier spring if I do decide to get a boat one day.

 

[SWUtah]

Violet springs from Toyota that are made by Eibach, is what the member used on his 200 series that has AHC/AVS. He said these are the ones used on armored Landcruisers in Europe. He documented his trip from north end of Africa to the tip of Cape Horn the south end. Maybe Beno has access to information on springs like this for a 100 series?

 

[Jack90210]

Does anybody have any updates? I was about to pull the trigger on these rear springs.

 

[Nishiki]

They show that they will arrive on Monday. I will probably install that same day. Give an update by no later than Thurs of next week.

EDIT: I actually purchased a pair off of eBay, an old LC100 series rears. Will post stats on those.

 

[nahtnoj]

Based on what you have spent so far you could of installed a bullet proof OME 2" lift. I think anyone with a 100 series AHC system needs to look at changing out to OME when they start having problems, unless you like to tinker with your suspension and deal on going with these issues.

I don't understand this line of thinking. If you replace the parts you won't have ongoing issues. You'll have a like new system that if properly maintained will last for another 150-200K. And you'll get all the features you truck was supposed to have.

 

[SWUtah]

I don't understand this line of thinking. If you replace the parts you won't have ongoing issues. You'll have a like new system that if properly maintained will last for another 150-200K. And you'll get all the features you truck was supposed to have.

Then if you think by replacing the failed parts on your 100 series AHC is a better option for you then that is what you should do. I know a Lexus service manager and service advisor in Las Vegas that owned LX's and could get the parts at cost for their rigs. They both decided to switch to OME. Their reason $$$

 

[drwapenshaw]

Then if you think by replacing the failed parts on your 100 series AHC is a better option for you then that is what you should do. I know a Lexus service manager and service advisor in Las Vegas that owned LX's and could get the parts at cost for their rigs. They both decided to switch to OME. Their reason $$$

Good lord. Some people find VALUE in the AHC. I am happy that it goes up when I want to go over something and my wife can still park it in the very cramped parking deck with low overhead downtown. The AHC rocks.

 

[Bubba68CS]

Then if you think by replacing the failed parts on your 100 series AHC is a better option for you then that is what you should do. I know a Lexus service manager and service advisor in Las Vegas that owned LX's and could get the parts at cost for their rigs. They both decided to switch to OME. Their reason $$$

You aren't addressing his point. You stated the issue was dealing with ongoing issues - not cost. He rebutted that by stating that a "new" system should be perfectly reliable for another 150-200k, as was the original system. Your acquaintances replacing their AHC because of cost doesn't rebut the point that a new AHC system shouldn't give any issues.

You are correct though in that every individual should do whatever they please with their own rig. Those with AHC issues should be aware of the potential cost of replacing the system.

 

[SWUtah]

You aren't addressing his point. You stated the issue was dealing with ongoing issues - not cost. He rebutted that by stating that a "new" system should be perfectly reliable for another 150-200k, as was the original system. Your acquaintances replacing their AHC because of cost doesn't rebut the point that a new AHC system shouldn't give any issues.

You are correct though in that every individual should do whatever they please with their own rig. Those with AHC issues should be aware of the potential cost of replacing the system.

Ok I'll play . I suggest that anyone wanting to keep their AHC going for or interested in fixing it do extensive searches. Second the AHC/AVS in the LX570 is much improved and more robust then the 100's but that makes sense since Toyota try's to evolve and improve these special vehicles. I've owned 3 LX470's two with less then 100k miles only problem with one of them was a bad AHC rear sensor that was replaced under warranty, corrosion issue lived in rust belt. My curren LX470 AHC started acting up at about 120k miles. Different stuff hard ride jerky jumpy ride. I looked into long term cost benefit and was advised by Lexus dealer and members of Mud that OME was the best and cheapest way to go. Can even tell you how expensive it would be to replace the "whole system"? If you start down the path of changing parts you better be an expert on the system or it will become a money pit. If I remember correctly several have had problems with their AHC before the 100k mile mark so thinking if you replaced the entire system you would be good for 150+ miles does not make sense. I love how my 100 rides with the OME 2" lift, plus I think it looks better. But that's just me several posters have presented great reasons why they love having their AHC and based on those reasons would repair their AHC. We all have different needs and reasons for our decisions. That's what makes Mud valuable you get to see different opinions and reasons why they are made.

 

[wopalx]

As an option to the eBay springs you can always buy a pair of rear springs from a standard land cruiser. They have a higher rating than the LX springs and can be found cheap with people upgrade their suspension.

Its what I did with my LX as it kept going into low when towing and fully loaded, sorted the issue and is not too harsh when unloaded.

 

[OregonLC]

If factory had only conventional shocks and [insert favorite vendor name] came out with an affordable AHC system we'd all be clamoring for it. Part of the dislike is in needing justification to mod. I often fall into that camp. Second to remote exploration modding is the best part of this gig. I think you could build an awesome AHC rig. I also think you could build an awesome OME rig. Both would be great and both would have their own limitations. Whatever you do, don't run a 35 or your truck will explode.

 

[Jack90210]

They show that they will arrive on Monday. I will probably install that same day. Give an update by no later than Thurs of next week.

EDIT: I actually purchased a pair off of eBay, an old LC100 series rears. Will post stats on those.

As an option to the eBay springs you can always buy a pair of rear springs from a standard land cruiser. They have a higher rating than the LX springs and can be found cheap with people upgrade their suspension.

Its what I did with my LX as it kept going into low when towing and fully loaded, sorted the issue and is not too harsh when unloaded.

Wow, this is the first place that I've seen that info. How do these springs compare to the stock LX470 springs in terms of load capacity?

 

[wopalx]

Wow, this is the first place that I've seen that info. How do these springs compare to the stock LX470 springs in terms of load capacity?

When I fist got my truck I loaded it fully (drawers, fridge, food, recover gear, luggage & camping gear for 5 PAX, fully loaded roof rack and boat with 100kg ball weight) and she sank down to LOW on the test run with myself and the kids.

The shocks and torsion bars in the LX are a lower load capacity than the LC ones as the AHC system holds a significant % of the vehicles mass. Where as on the LC the springs and torsion bars hold the whole vehicles mass as there is no AHC system in the middle.

So I did some checking and physically the LC springs are larger in DIA than the LX ones, so I installed them and no issues when fully loaded

If I fully unload the LX now the rear is bouncy, suggesting its over-sprung with the LC springs, but as I'm keen to install a rear bar shortly I think the extra weight will remove that issue.

 

[dfrelich]

If we spend our lives listening to others what we should do. We will never be happy. I come to this forum to gather and share information.

Ultimately I make final decision based on information I gather.

I replaced globes for $600 from oversea. Look at other post I made. I am pleased with the decision.

Even more surprising is that I replaced all end links with new bushings as well as sway bar bushings. Rubber were almost dry.

Now I'm even more happy with the ride. Especially long trips we take few times a year.

AHC is awesome.

 

[whitenoise]

Thanks for sharing your findings. I'd like to know how much of a difference the 10mm spacer made to your neutral pressure, and if you did it back-to-back with the same payload etc. in the truck. What kind of spacer was it (rubber, metal etc).

I guess I don't see how it cannot make any appreciable difference to the neutral pressure - Basically you're raising the back of the truck 10mm which should drop the pressure significantly.

 

[PADDO]

Thanks for sharing your findings. I'd like to know how much of a difference the 10mm spacer made to your neutral pressure, and if you did it back-to-back with the same payload etc. in the truck. What kind of spacer was it (rubber, metal etc).

I guess I don't see how it cannot make any appreciable difference to the neutral pressure - Basically you're raising the back of the truck 10mm which should drop the pressure significantly.

I achieved between 0.2 and 0.3MPa drop in rear pressure with 10mm trim packers onto stock used AHC coils. Personally I no longer see installing 10mm spacers/packers as a "fix" worth the effort. New coils and 10mm packers at stock height/weight will get you down around 6.2 - 6.3 MPa, next iteration I'll go with new coils and 30mm spacers, possibly airbags too. These aging systems seem to like their rear neutral pressure towards the low end of their spec range. Most spacers/packers are polyurethane.

 

[whitenoise]

Paddo - I see what you're saying. However, being that coil springs lose only their preload and not their spring rate (referred to as "spring sag" or "taking a set") over a period of time, I'd venture to say that replacing springs with new OEM ones isnt really getting you anything, other than the ~$200 or so out of your pocket and a minimal amount of gain in travel. A pair of spacers should do the trick - perhaps you're right with the 30mm spacer being the right number? (30mm = close to 1MPa drop in neutral pressure).

 

[PADDO]

Paddo - I see what you're saying. However, being that coil springs lose only their preload and not their spring rate (referred to as "spring sag" or "taking a set") over a period of time, I'd venture to say that replacing springs with new OEM ones isnt really getting you anything, other than the ~$200 or so out of your pocket and a minimal amount of gain in travel. A pair of spacers should do the trick - perhaps you're right with the 30mm spacer being the right number? (30mm = close to 1MPa drop in neutral pressure).

Ok. It's not so much about the constant spring rate but the load rate/design rate i.e the weight the spring is designed to support at a certain height. We all know that rear neutral pressure is a function of height (and weight but we will just focus on height) and springs that have set, lost free length, do not provide the height support the AHC system needs, hence the height sensor reads a greater error displacement signal and commands the pump to run longer to achieve zero displacement signal and we get a higher static pressure. Here are two recent examples of corrective AHC action I've had the pleasure to be involved with. Guy 1 replaced AHC coils and installed 10mm packers and his rear pressure went from 7.2 to 6.5 and guy 2 installed coils only and went from 7.3 to 6.8. I have other notes/txts/emails from several other guys around the world who have pretty much the same results. From this small sample and my own experience it suggests to me that if you have rear neutral pressures at or above 7.2 then new, unset, coils alone won't get you into the lower range of Toyotas 5.6 -6.7 range, neither will packers alone. You might hit the upper range. Further experimentation suggests that as these systems age they "seem" to provide better damping when rear neutral pressure is closer to 5.6 - hence new full length coils to get you down .5 or so and maybe 30mm spacers to buy another .6 to .9 MPa. I'll order some man a fre 80 series 30mm packers and install them and do back to back pressure tests to gather more data. I do agree that if you have a system where the rear neutral pressure is in range or only marginally high then just 30mm packers will provide a decent result. Of course this all assumes you aren't paying for labor to experiment. So for me I stand by new, unset coils and 30mm packers to get down low in the spec range. YMMV.

 

[whitenoise]

Understood, point well taken. Based on my understanding of the system, i feel this is the most efficient route for refreshing the system:
1. Bleed and refill system with fresh fluid.
2.. Measure baseline pressure with truck at curb weight (full fluids). When I measured, I was outside the vehicle and used a broom stick to reach the height switch - procedure says to lower to L, then back to N for reading pressures.
3. Measure ride height using Toyota's procedure and correct to lower end of range (I.e. truck sits at highest recommended ride height) using torsion bar adjustment and replacing coils/packers. (Haven't done this yet)
4. Adjust ride height sensors to read zero offset at this height.
5. Remeasure neutral pressure, now it should be close to the low end of the scale.

 

[PADDO]

Understood, point well taken. Based on my understanding of the system, i feel this is the most efficient route for refreshing the system:
1. Bleed and refill system with fresh fluid.
2.. Measure baseline pressure with truck at curb weight (full fluids). When I measured, I was outside the vehicle and used a broom stick to reach the height switch - procedure says to lower to L, then back to N for reading pressures.
3. Measure ride height using Toyota's procedure and correct to lower end of range (I.e. truck sits at highest recommended ride height) using torsion bar adjustment and replacing coils/packers. (Haven't done this yet)
4. Adjust ride height sensors to read zero offset at this height.
5. Remeasure neutral pressure, now it should be close to the low end of the scale.

I always like an evidence based plan
My thoughts:
Point 1. Absolutely.
Point 2. Having baseline pressures correlated to vehicle height is good.
Points 3&4. Remember the height sensor displacement signal sets height, not TB cranking and adding packers. With your vehicle off if you put say 10 turns on the TBs the front will lift because of the additional torsional force, then as soon as you start the vehicle the front height sensors "see " the positive error signal (too high) average and invert that signal and the ECU tells the front leveling valve to lower until the error approaches zero. So you're back at the same height but now your front neutral pressure is low because of all the torsion you cranked in. So recommend adjust height and cross level before dialing in neutral pressures.
Point 5. Yes, it's an iterative process, adjust height, then pressure, rinse and repeat.
Edit: and after height and neutral pressures are set is a good time to get a baseline "globe health check" reading. Doing the globe health check with neutral pressures way out of whack won't give you an accurate reading.