Looking for some AHC pressure thoughts

[TheSackettWay]

Hey guys, I am just looking to make sure that my understanding on my AHC system is somewhat correct. I have been reading every post possible for the last month and trying to build a good grid for it, and for how to move forward making it healthy.

I live in Northern Iraq and have a 2006 LC with AHC. I’ve had it about a year and love it (had an ‘02 LC in the States before we lived over here), but in the last couple of months as it became a bit bouncier, I began researching AHC.

All I have done to it is an AHC flush…..but everything else is quite unhealthy. The test for the globes shows only about 6 graduations, which I know means failed globes. It raises and lowers with speed and there is definitely a difference in sport vs. comfort, but sport can still be bumpy, especially with luggage and a full load of passengers, or big bumps at low speed (which Iraq is quite full of).

It’s been hard for me to find my own Techstream cable here, but I went to a friend’s shop today and used his computer, which showed insanely high pressures (which I expected).

Front was 10.2

Rear was 8.3

I want to change all four globes and I want to do a sensor lift, the right way…with shock spacers and such.

With all of this, I am trying to decide what my plan of action should be.

Unfortunately I may not be able to get new globes for a few months. We are quite used to the bad ones….should I go ahead and crank the torsion bar a ton…and maybe find some stiffer shocks for the rear?

Just to confirm, if I do that now and try to bring the pressures down, will the pressures get totally changed again once I have new globes? According to my understanding globes don’t actually change pressure.

Or should I wait on working on the pressures, and just get four new globes as fast as I can (it may be several months out still), and once those are on the truck work on the pressures?

I guess the basis of my question is, even with totally shot globes, is it worth fixing the pressures for these next few months? And will that fixed pressure stay fixed with the future new globes?

Also, with my pressure so high, is there still hope that my front can be helped via the TB? It seems even if I do many full turns, it might still be out of spec.

Thanks for your thoughts!

 

[uHu]

• You are right in that there is no connection between bad globes and measured pressure.
• To bring the pressure down, you need new rear coil springs, and to crank the front torsion bars.
• There are no shocks as such on this car, so "changing to stiffer shocks" is a sentence without any meaning or relevance. The damping (shock function) is in the valve body sitting between the globe and the "shock". The "shock" is just a hydraulic ram, pressurised by the ahc fluid.
• To get suspension damping, you need globes with more pressure than what you have now, and you need to bring the pressure down to specs. With no movement in the gas in the globes, there will be no damping, and no suspension movement. In order to get a good grip of the road, especially in curves and when braking, you need good damping. (On a normal suspension system, you change the shocks. Here you have very good shocks (gas spring - valve body - "shocks"), you just need the gas springs (globes) and the steel springs to do their part of the job)
• If you want a lift as well, you need even stronger springs, and this is a bit of an art form when dealing with AHC and getting the pressures right, especially if you need to drive with varying loads. There is also the limiting factor of the angles of the A-arms on the front suspension, seriously limiting lifting possibilities, (or giving up on drivability).

If the car is going to operate in the area where it is now, it might be worth considering scrapping the AHC and install regular Land Cruiser springs and shocks. I do like the AHC, and am trying to keep it going, but, if I were to operate in remote, rough areas, I would rather rely on something simpler than the fantastic AHC TEMS. It is very nice to drive without feeling pot holes and wash boards, but it's even better to be able to drive from A to B without breaking down.

 

[TheSackettWay]

• You are right in that there is no connection between bad globes and measured pressure.
• To bring the pressure down, you need new rear coil springs, and to crank the front torsion bars.
• There are no shocks as such on this car, so "changing to stiffer shocks" is a sentence without any meaning or relevance. The damping (shock function) is in the valve body sitting between the globe and the "shock". The "shock" is just a hydraulic ram, pressurised by the ahc fluid.
• To get suspension damping, you need globes with more pressure than what you have now, and you need to bring the pressure down to specs. With no movement in the gas in the globes, there will be no damping, and no suspension movement. In order to get a good grip of the road, especially in curves and when braking, you need good damping. (On a normal suspension system, you change the shocks. Here you have very good shocks (gas spring - valve body - "shocks"), you just need the gas springs (globes) and the steel springs to do their part of the job)
• If you want a lift as well, you need even stronger springs, and this is a bit of an art form when dealing with AHC and getting the pressures right, especially if you need to drive with varying loads. There is also the limiting factor of the angles of the A-arms on the front suspension, seriously limiting lifting possibilities, (or giving up on drivability).

If the car is going to operate in the area where it is now, it might be worth considering scrapping the AHC and install regular Land Cruiser springs and shocks. I do like the AHC, and am trying to keep it going, but, if I were to operate in remote, rough areas, I would rather rely on something simpler than the fantastic AHC TEMS. It is very nice to drive without feeling pot holes and wash boards, but it's even better to be able to drive from A to B without breaking down.

• You are right in that there is no connection between bad globes and measured pressure.
• To bring the pressure down, you need new rear coil springs, and to crank the front torsion bars.
• There are no shocks as such on this car, so "changing to stiffer shocks" is a sentence without any meaning or relevance. The damping (shock function) is in the valve body sitting between the globe and the "shock". The "shock" is just a hydraulic ram, pressurised by the ahc fluid.
• To get suspension damping, you need globes with more pressure than what you have now, and you need to bring the pressure down to specs. With no movement in the gas in the globes, there will be no damping, and no suspension movement. In order to get a good grip of the road, especially in curves and when braking, you need good damping. (On a normal suspension system, you change the shocks. Here you have very good shocks (gas spring - valve body - "shocks"), you just need the gas springs (globes) and the steel springs to do their part of the job)
• If you want a lift as well, you need even stronger springs, and this is a bit of an art form when dealing with AHC and getting the pressures right, especially if you need to drive with varying loads. There is also the limiting factor of the angles of the A-arms on the front suspension, seriously limiting lifting possibilities, (or giving up on drivability).

If the car is going to operate in the area where it is now, it might be worth considering scrapping the AHC and install regular Land Cruiser springs and shocks. I do like the AHC, and am trying to keep it going, but, if I were to operate in remote, rough areas, I would rather rely on something simpler than the fantastic AHC TEMS. It is very nice to drive without feeling pot holes and wash boards, but it's even better to be able to drive from A to B without breaking down.

Thanks so much for your reply @uHu. Many of your past posts have helped me go from zero understanding to the little bit I have now! Yes, I live in Iraq, but when you say remote, rough areas, we may be thinking of different sort of areas. I’m here, but really I have access to parts. There are several Toyota dealerships with OEM parts. I am able pretty easily to ship any part from other countries here. So my main difficulty to parts isn’t access but rather just finances, being able to purchase one small thing at a time. Yes it’s been hard to get my hands on my own techstream type computer to have at my house, but ultimately I can always pop into my friend’s shop and check pressures with his.

When I said “stiffer shocks,” I’m sorry, I meant “stiffer springs” for the rear.

I get the simplicity of a regular suspension system….but could it be true….as I’ve seemed to gather from all of the AHC information on these forums, that if my suspension system had new globes, and otherwise was healthy, that it can be a very reliable and robust system? There isn’t a speck of rust on the truck.

If this was your truck, with these high pressures, and you were wanting to keep AHC, how would you move forward. Taking the sensor lift out of the picture…..yes I need to crank the TB, but I feel like I haven’t heard of anyone else’s pressure quite this high. Do you think that I can adjust the TB many many full turns and it really do the trick for the front, without needing it reindexed?

And for the rear…..it seems my options are new AHC springs, Kings springs, and non-AHC springs. All of these ultimately I can get here…..AHC springs and non-AHC springs are a dime a dozen here, and I could ship in Kings springs if that is better. I don’t plan on the truck ever having any serious serious armor….maybe one day a simple swing out off of the stock bumper…..but yes, sometimes it’s loaded down with 7 passengers or quite a bit of luggage on road trips, and a rear-hitch cargo basket.

I know non-AHC springs are not designed to be used in conjunction either AHC, but with my extremely high pressures could that be a better solution for me? Or would you think that Kings with a spacer may be better?

Lastly, adding the sensor lift back into the equation….if I do that and do it the correct way….with the correct spacers from Dave Stedman…..do you forsee me needing Kings springs, maybe even with a spacer, or non-AHC springs? It seems when @DirtDawg did this, Kings worked well for him.

Seriously, thank you for your thoughts.

 

[uHu]

Yes, I don't know Iraq well, having been only in the very south, close to the gulf, outside Basra, just after the little warring going on there. (Building networks and microwave links). I guess I presumed something about road conditions after seeing the "overhead cable conditions" in your pictures .

If it were me, I would get new globes, adjust the torsion bars and re-index if required, and get new coils, purple.
If I were to carry both 7 passengers and a hitch basket, I would fit Kings. Problem with Kings is that with an empty car, the pressure is too low to get good damping.
If the car had more than about 200 k km, I would get new height sensors as well, before they fail (wear out).

The three main enemies of the AHC system, as I see it, are: Lack of maintenance (included lack of knowledge), rust, and forest roads where sticks can interfere with height sensors, linkages and cables.

 

[TheSackettWay]

Yes, I don't know Iraq well, having been only in the very south, close to the gulf, outside Basra, just after the little warring going on there. (Building networks and microwave links). I guess I presumed something about road conditions after seeing the "overhead cable conditions" in your pictures .

If it were me, I would get new globes, adjust the torsion bars and re-index if required, and get new coils, purple.
If I were to carry both 7 passengers and a hitch basket, I would fit Kings. Problem with Kings is that with an empty car, the pressure is too low to get good damping.
If the car had more than about 200 k km, I would get new height sensors as well, before they fail (wear out).

The three main enemies of the AHC system, as I see it, are: Lack of maintenance (included lack of knowledge), rust, and forest roads where sticks can interfere with height sensors, linkages and cables.

Hahaha, this really made me laugh. Yes, electricity here is an absolute nightmare….the entire nation runs on generators for more than half the day.

70% of the time our car is just a family hauler, two small kids and regular things like kids bikes in the back, not heavy at all. 30% of the time it’s maxed out with people and occasionally people and luggage.

Could some new purple springs and maybe a spacer be a happy medium between purple and Kings?

I hope it’s okay to just keep coming back with further questions…I’ve been constantly reading about and thinking about this for two months, but with not one person to actually talk to about it.

And also, if I did go through with a sensor lift, maybe 2 inches…..does that then absolutely require a spacer for the spring to still help keep glove pressure down?

 

[NE Snowman]

So my main difficulty to parts isn’t access but rather just finances

I hate to be the guy but, this is not a cheap platform. parts are only designed for 100s it doesn’t share with anything else.

Globes before you go down some rabbit hole of lifting the truck for almost no reason. Once lifting you put more stress on other joints which then need replacing. And you are not going to like the price of new lowers or uppers or FDS. Get the AHC back in working order, it’s most likely cheaper than a whole suspension + non AHC torision bars.

I don’t know what options are out there in that area but an LC has got to be one of the more expensive SUVs to maintain. Just trying to be the voice of reason.

 

[TheSackettWay]

I hate to be the guy but, this is not a cheap platform. parts are only designed for 100s it doesn’t share with anything else.

Globes before you go down some rabbit hole of lifting the truck for almost no reason. Once lifting you put more stress on other joints which then need replacing. And you are not going to like the price of new lowers or uppers or FDS. Get the AHC back in working order, it’s most likely cheaper than a whole suspension + non AHC torision bars.

I don’t know what options are out there in that area but an LC has got to be one of the more expensive SUVs to maintain. Just trying to be the voice of reason.

Voice of reason definitely welcomed and probably needed. Thanks man for it. I do think it’s in my best interest to get the pressures in spec as @uHu is saying….and my next thing is to get those new globes as soon as I can. I think my itch for the sensor lift mostly just comes from wanting to be different from the next 100 series over.

Yes, used Land Cruisers here are definitely much more expensive than the west. Parts really seem hit or miss….they are available both OEM and aftermarket….and some OEM parts are way cheaper, some more. To just simply maintain it and do so with mostly OEM is probably actually cheaper here, and labor for things I can’t do myself is much much cheaper, though for things like that I usually try and research as much as I can and then do it along with the mechanic to make sure he doesn’t do anything crazy.

I will say, this is the land of Land Cruisers. They are everywhere here, and all different eras of them. Everyday no matter where I go here, there are dozens of cruisers around on the same road. Pretty fun.

 

[TheSackettWay]

Voice of reason definitely welcomed and probably needed. Thanks man for it. I do think it’s in my best interest to get the pressures in spec as @uHu is saying….and my next thing is to get those new globes as soon as I can. I think my itch for the sensor lift mostly just comes from wanting to be different from the next 100 series over.

Yes, used Land Cruisers here are definitely much more expensive than the west. Parts really seem hit or miss….they are available both OEM and aftermarket….and some OEM parts are way cheaper, some more. To just simply maintain it and do so with mostly OEM is probably actually cheaper here, and labor for things I can’t do myself is much much cheaper, though for things like that I usually try and research as much as I can and then do it along with the mechanic to make sure he doesn’t do anything crazy.

I will say, this is the land of Land Cruisers. They are everywhere here, and all different eras of them. Everyday no matter where I go here, there are dozens of cruisers around on the same road. Pretty fun.

@NE Snowman I should say 100 series are way more expensive to buy here than the west but cheaper to maintain even with most genuine parts.

 

[IndroCruise]

@NE Snowman I should say 100 series are way more expensive to buy here than the west but cheaper to maintain even with most genuine parts.

Just to add .....

I have King KTRS-79 Rear coils under my 2006 LC100 with AHC (almost stock except for ARB Deluxe Front bar). With the vehicle unloaded this gives around 5.3Mpa Rear AHC pressure. This is lower than the FSM-specified range but damping is still good, ride comfort slightly firmer, but still very acceptable, no regrets, and gets better with load rather than worse!

For parts, presume you have considered nearby https://partsouq.com/ for good pricing and speedy response??

 

[TheSackettWay]

@IndroCruise @uHu All of this time later I finally able to order new globes.

I cranked my torsion bars since we last spoke and with this my pressures went from 10.2 to 6.5 in the front, and from 8.3 to 7.6 in the rear.

I am leaning towards ordering Kings springs along with the new globes. I am okay with it being a slightly stiffer ride when car is empty, if when the car is full of people/hitch basket installed it goes into spec pressures...but I wanted to ask your opinion: If I've now got 7.6 in the rear now with the original/worn out springs, will the Kings surely put it way way too under pressure, or maybe just slightly under pressure and I'd be good to go?

You mentioned purple springs, but it seems a little harder to find them, and I can easily get the Kings springs here.

I'm thinking in the coming year we will start doing some longer road trips, in which case we would have both the hitch basket or a hitch bike rack and also add a roof rack carrier, so that might add a little bit more weight, hence maybe Kings are the way to go. I just have like an ounce of worry that if I get these things here then Kings will be way way too stiff/put me way too far under pressure. But based on reading all of the testimonies here on IH8MUD it seems mostly people are pleased with mostly stock vehicles paired with Kings....that it's a slightly firmer ride but dampening is still there, and gets better when they load the car down for trips.

Also I am thinking way less about my desire for the AHC lift and way more practically, as in I don't actually need that lift/am just fine without it....but I guess if they pressure is slightly low, that could always be another option too to help get into spec pressures.

 

[thibaut]

For the rear springs, you can simply add a spacer. This is super cheap and will add 1/2 or 1 inch of compression to the spring, reducing the load on the AHC. That is very cheap.
Then you have to bite the bullet and order new spheres. If you were in Europe, I would advise Pleiades in the uk. But in the Gulf just use partsouq or amayama warehouse in dubai.
I wouldn’t lift.

 

[TheSackettWay]

For the rear springs, you can simply add a spacer. This is super cheap and will add 1/2 or 1 inch of compression to the spring, reducing the load on the AHC. That is very cheap.
Then you have to bite the bullet and order new spheres. If you were in Europe, I would advise Pleiades in the uk. But in the Gulf just use partsouq or amayama warehouse in dubai.
I wouldn’t lift.

Thanks for the response brother! My sphere's/globes are for sure bad, so I have some on the way regardless. I know the pressure's aren't connected to the health of the globe but my globes are failing so they are still an issue. Also, yes I know I can do spacer, but with me being right now a 7.6 in the rear without the loaded hitch basket and without 7 adults in the car, I feel pretty confident a spacer isn't going to be enough to get my pressures back into spec. My only concern is that Kings springs will be slightly too much of a drop in pressure...but as I've talked with some others on here, I feel pretty good to go with the Kings springs.

 

[IndroCruise]

@IndroCruise @uHu All of this time later I finally able to order new globes.

I cranked my torsion bars since we last spoke and with this my pressures went from 10.2 to 6.5 in the front, and from 8.3 to 7.6 in the rear.

I am leaning towards ordering Kings springs along with the new globes. I am okay with it being a slightly stiffer ride when car is empty, if when the car is full of people/hitch basket installed it goes into spec pressures...but I wanted to ask your opinion: If I've now got 7.6 in the rear now with the original/worn out springs, will the Kings surely put it way way too under pressure, or maybe just slightly under pressure and I'd be good to go?

You mentioned purple springs, but it seems a little harder to find them, and I can easily get the Kings springs here.

I'm thinking in the coming year we will start doing some longer road trips, in which case we would have both the hitch basket or a hitch bike rack and also add a roof rack carrier, so that might add a little bit more weight, hence maybe Kings are the way to go. I just have like an ounce of worry that if I get these things here then Kings will be way way too stiff/put me way too far under pressure. But based on reading all of the testimonies here on IH8MUD it seems mostly people are pleased with mostly stock vehicles paired with Kings....that it's a slightly firmer ride but dampening is still there, and gets better when they load the car down for trips.

Also I am thinking way less about my desire for the AHC lift and way more practically, as in I don't actually need that lift/am just fine without it....but I guess if they pressure is slightly low, that could always be another option too to help get into spec pressures.

Late back to the party but here are some thoughts, as requested .....

Faced with similar concerns on my 2006 LC100 Sahara with AHC/TEMS in Australia, in October 2019 I replaced the OEM AHC/TEMS Rear Coil Springs (Purple Patch) with Australian-made King Springs KTRS-79 -- https://kingsprings.com.au/catalogue/product/864/ktrs-79 -- also available from various distributors and some eBay sources (check reliability of sources). I was not pursuaded that spacers/packers were sufficient for my application.

I also added airbags inside the King Rear coils -- but this was/is over the top -- yet to be used in anger and if used almost certainly would be imply loads which would cause the Gross Vehicle Mass (GVM) of 3,260kg (7,188 pounds) to be exceeded! In Australia, if a vehicle is overweight (meaning weight of the vehicle plus everything in or on the vehicle including persons and their stuff (everything!) exceeds the certified and plated GVM), then the vehicle is unroadworthy for use on Australian public roads. In the event of a roadside check or an accident, being unroadworthy involves all sorts of legal and insurance repercussions should an accident occur on Australian public roads, might be different off-road. The 'rules' also may be different in other countries and jurisdictions. In our case, usually just Mr and Mrs Indrocruise were travelling, so containing ourselves to 3,260kg was not too hard.

Anyway, back to the springs ....

Initially, my Rear AHC pressure was a bit low at 5.3Mpa after fitting the King KTRS-79 springs -- not optimal for damping and gave a slightly more firm but still comfortable ride, certainly not intolerable, and of course better when loaded for travel. 'Ride quality' is somewhat subject to personal preferences.

Some of the firmness was down to the choice of actual tyres -- BFG 275/65R17 121/118S KO1 (succeeded by KO2), "E" rated, running at 40psi on sealed highways -- so this is a fairly stiff arrangement. Less pressure is used on backroads and trails to match the conditions.

'Globes' and AHC Fluid were still relatively new and showed a difference of 14+ graduations between "LO" height and "HI" height at the AHC Tank at close to FSM specification pressures and ride heights at "N" height -- so 'globes' could be taken as 'Good!' with no adverse effects on damping and ride quality.

After some further 'fine tuning' -- tweaking at the Front Torsion Bars and a small lift adjustment by slightly re-positioning the Rear Height Control Sensor, then settings and outcomes were as follows:

Actual tape-measured Hub-to-Fender heights (same both sides within FSM tolerance of +/- 10 mm, AFTER Front cross-levelling):

Front: 490 millimetres (19.3 inches)
Rear: 540 millimetres (21.3 inches)

Actual Height Control Sensor readings on all new Toyota/Lexus/AISIN OEM Sensors -- Front Left, Front Right, Rear:
All close to zero -- better than FSM tolerance of +/- 5 millimetres (+/- 0.2 inches)

Actual AHC pressures:

Front: 6.9Mpa;
Rear: 5.7Mpa

Compare Actuals with these Toyota/Lexus recommendations for an unloaded vehicle with fuel full at "N" height (for optimum damping and ride quality):

FSM-specified heights -- too hard to measure per FSM so IH8MUD Hub-to-Fender recommendations are used:
Front: 500 millimetres (19.7 inches)
Rear: 520 millimetres (20.5 inches)

FSM-specified AHC Pressures:
Front: 6.4MPa to 7.4Mpa;
Rear: 5.6Mpa to 6.7MPa without sub-fuel tank and total fuel of 96 litres
Rear: 5.9Mpa to 7.0MPa with sub-fuel tank and total fuel of 145 litres (my vehicle)
Height Control Accumulator: ~10.5Mpa (IH8MUD recommendation)

Toyota OEM Tyre Recommendations on B-pillar plate (LC100 Sahara with IFS in Australia):
Pressures: 200 to 220 kPa = 29 to 32 psi

CONCLUSIONS ON ACTUAL CONFIGURATION:

• Front Hub-to-Fender height is slightly low,
• Rear Hub-to-Fender height, and, Front-to-Rear 'rake' are both slightly high,
• Front and Rear AHC pressures are reasonable,
• Further 'tweaking' was considered (such as increasing Front Hub-to-Fender height and reducing Front-to-Rear rake) but such changes were deferred pending long term review of 'ride quality' by my daughter, son-in-law and young familly who now operate this 2006 LC100 Sahara with fully operational AHC/TEMS,
• BFG 275/65R17 121/118S KO2 (or similar or better all-terrain tyres) will be retained, operating at 40psi but with pressures lowered to suit off-highway conditions -- different for rocks, gravel, mud or sand -- no snow in Western Australia,
• More than five years later -- no regrets. After many trips on trails around Western Australia, the above actual settings have been left unchanged,
• The family have advised that no further adjustments are necessary -- they continue to enjoy the comfort and ride quality provided by real time auto self-levelling, real time auto damping variation and real time auto roll/pitch/squat resistance, all provided by AHC/TEMS. They consider the vehicle very reliable and suitable for long distance trips under all road and trail conditions in remote locations anywhere in Australia, and the rarely used facility for "LO" and "HI" heights is 'nice to have'.

The bottom-line is that after Rear spring modifications/upgrades for better load-carrying capacity, some 'fine-tuning' can be done by adjusting heights, and can include a small Rear 'sensor lift' and adjustments to Front torsion bar settings until an acceptable arrangement with reasonable AHC pressures and good 'ride quality' is found -- while avoiding excessive lift for the reasons mentioned by @uHu in Post #2 this thread, especially where reliability and avoidance of breakdowns is important.

An important point is to mark all changes being made on relevant parts and keep good records and photographs so that a personal assessment of the effect of the changes can be made and can guide reversals or further changes if required.

Late Edit -- Side Notes:

Height Control Sensors:
These have not been mentioned in the inquiry by @TheSackettWay. These ‘wear items’ are located in the harsh underbody environment -- exposed to hot, cold, mud, sand, sticks, stones, etc. As mentioned by @uHu, these Sensors are longlasting but like other wear items -- they do eventually ‘wear out’ or are damaged or degraded and fail, sometimes with mixed and confusing symptoms. Lack of a Height Control Sensor DTC does not by itself provide assurance that the Sensor is healthy. On a vehicle which is now 19 years old, it is worth including replacement of these 'vital-to-AHC/TEMS' Height Control Sensors in the maintenance plan -- with NEW, definitely not ‘pre-owned’ parts, nor non-OEM substitutes. Some details, Part Numbers and discussion can be found in this post:
Height control sensor - https://forum.ih8mud.com/threads/height-control-sensor.1306616/#post-14851883
Parts pricing might best be obtained from ParImpex.or Impex or possibly Megazip.

AHC Pump Sub-assembly:
Also not mentioned in the inquiry -- but depending on how conservative and reliability-focussed an Onwer may want to be, and given that the AHC/TEMS system will be completely disrupted anyway to fit replacement ‘globes’, this may be the right opportunity to replace the AHC Pump sub-assembly Part Number 48901-60010 -- with a NEW, definitely not a ‘pre-owned’ part, nor a non-OEM substitute. Replacement is not a difficult nor long job -- it is well-described at:
AHC pump removal with pics - https://forum.ih8mud.com/threads/ahc-pump-removal-with-pics.1227554/
Again, parts pricing might best be obtained from Partsouq or Impex or Megazip.