Definitive list of AHC maintenance items (3 Viewers)

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

20181214_144636.jpg


Update to my risky decision installing 80 series Dobinson springs in the back (standard height spring) on sensor lifted LX470. Driven 10k miles now.

The springs have taken a good amount of driving to settle and get to the same comfort levels that I am used to having. After a 300lb combined weight of of a Dissent rear bumper and spare tire, I still have amazing comfort with full AHC capabilities. Took a pressure reading and was excited to see how capable this setup can be in the future. 06 LX has nearly 200k miles, rear shocks replaced at 150k, all Globes and accumulator as well as front shocks are still original. 13 ticks on the graduation level.
20190630_203413.jpg


4.1 MPa-g! The shocks start to shut off partially at around half a tank of fuel, but the dampers continue give a good ride. Once filled up there is no problem. Its ready to take anything I throw in it!
 
Last edited:
Okay, so I've read through the whole thread and understood everything. I must say a big big thank you for all the information and contribution found inside here!

I had a feeling that this is going to be a walk in the park now that I know everything:)) Boy, was I wrong..

So I started with cross-leveling the truck, one turn CW on the DS, one turn CCW on the PS, and N->L->N after every adjustment-pair.

I've got it spot on to where it should be, 19.75" both sides.

Okay cool, I thought, lets go around the block and see the pressures, and so I did. Pressures where at 8.5 - wow. So I've stopped and measured the hub center to fender lip again just out of curiosity...

Now here is where the tricky and abnormal from everything I've read comes:

It was again leaning to the PS side.

So I've cross-leveled it again, and again and again.. Pressures came down into the high 6'es, but if I take it for a ride it then still leans towards the PS side. I've pretty much bottomed out the DS adjuster, and the PS is almost all the way unwound, but no matter what I do, after a short ride it leans to the PS side. The front now is supper harsh as well, I guess because the preload is way too high on the DS side. I'd bet if I'd connect a gauge, DS would read something like 2mPa and the PS would read something like 11 mPa.

At this point I'm starting to think that the sensors on the front actually DO MATTER in terms of cross leveling - as those are the only things I haven't touched in the process, and one (DS) is almost all the way up in the slider, while the other (PS) is all the way down in its slider.

I'm pretty much lost at this point and have no idea how to advance, but I have a feeling that I should set the sensors both to the bottom of their tabs, and do the crossleveling again from there. And by this I mean, turn the TB's until both sensors read 0. Anyway I kind of lost my mind during this 2 hour torture, so I gave up for the day:))
 
Last edited:
Time to go the other way around the block. Instead of NASCAR turns to the R, make L turns...

:):rofl:

Sorry, I have nothing.

You could switch the torsion bars side to side. But I would probably get obsessed with the sensors at this point...

LOL, not a bad idea:)))

On the TB's.. I have a feeling, but not sure that there could be two issues with them:

1, Someone took it apart earlier and they're not indexed the same way
2, After 20 years of load, they now have different spring rates.

Anyway, there is no way I'm pulling them, as they look rusted solid into the anchors.

But I think the most plausible thing is that the pressure in the front "shocks" are different, caused by the sensors. I don't know though how this is possible knowing that the front is a single hydraulic circuit with the "shocks" being connected - at least when stationary...
 
Okay, went back and played around.. Adjusted the TB's again. Perfect until I take the car for a ride - after that the lean is back.

I wonder if there is something going on with my sensors, as the closest I can get them is around 10mm (DS-PS), now it is (8mm - (-4mm)) = 12mm, while the DS is all the way up in the tab, and PS is all the way down in the tab.

Is it possible to zero/calibrate these things? I've tried removing the battery terminal & reseting the ECU via a clip in the DLC3, but didn't do anything.

Or perhaps my chassis is twisted?
 
Okay, went back and played around.. Adjusted the TB's again. Perfect until I take the car for a ride - after that the lean is back.

I wonder if there is something going on with my sensors, as the closest I can get them is around 10mm (DS-PS), now it is (8mm - (-4mm)) = 12mm, while the DS is all the way up in the tab, and PS is all the way down in the tab.

Is it possible to zero/calibrate these things? I've tried removing the battery terminal & reseting the ECU via a clip in the DLC3, but didn't do anything.

Or perhaps my chassis is twisted?
Will try and help, with a few questions, etc.
You should be able to adjust the difference between the 2 front sensors, either by adjusting them (when the car is level L/R), or by servicing or changing them, if they give erratic readings. Are the linkages good/smooth with no slack or binding.

Did you bleed? When bleeding the front, either side, you should see that both sides go down.

What is your rear pressure? If your rear springs have not been changed the last 5 years, it's probably time. The lean might come from the right side coil being too weak (compared to the left). It is relatively easy to pick the coils out and check/compare them. Do they have color markings? (A small paint spot)
 
Last edited:
Will try and help, with a few questions, etc.
You should be able to adjust the difference between the 2 front sensors, either by adjusting them (when the car is level L/R), or by servicing or changing them, if they give erratic readings. Are the linkages good/smooth with no slack or binding.

Did you bleed? When bleeding the front, either side, you should see that both sides go down.

What is your rear pressure? If your rear springs have not been changed the last 5 years, it's probably time. The lean might come from the right side coil being too weak (compared to the left). It is relatively easy to pick the coils out and check/compare them. Do they have color markings? (A small paint spot)

1, The height sensors: They're hacked a bit IMO.. first of all, the ones at the front.. they don't have the stock linkage. PO did something to them & now it has some sort of other linkage - 9cm (~3.5inch) long, fixed length, no adjusting possibility on that. The only adjustment I can do is sliding them up/down in the UCA tab.
Second, the sensors are hacked in that way that the original 3 springs have been replaced with springs from ball point pens (as the originals cracked/rusted/etc) - I can imagine this throws off the calibrated value as the springs now probably have different resistance - I think this is why I can't get the front ones to read the same reading no matter what I do. The closest they are is when one is pushed to the very top of the tab, while the other is all the way at the bottom of the tab.
That said, the rear sensor's linkage is stock, but I think the 3 spring mod had been carried out on that as well - as even if I set it to the heighest setting on the rear upper control arm in the sliding tab, it will not raise the back 0.5" more than the front.
All 3 linkages have a good slack in them of course. Not much, but it's there.

2, I did not bleed. I have a feeling that I should order new bleed nipples, as they're rusted pretty badly, so chances are nothing is going to go through them if I manage to losen them.

3, Rear pressure is 6.5 right now - which is interesting looking at the state of the springs - totally rusted. There is no way to read the paint markings from them anymore. Even that, I think the TB's should correct the left to right lean introduced by the rear weak springs.

I think I should replace the sensors, springs, globes, shocks as a minimum, and even then I might need new actuators - if the bleed nipples start to act up (like snap off). As much as I would love to retain the AHC for it's superplush ride, because of this I'm really starting to consider ripping out the system and going with a simple lift kit. If I compromise the ride quality (I really would hate to do that, but at the end of the day we're talking about a comprimised harsh ride vs. not being able to use the car at all) I could save a ton of money there looking at all the expensive parts that needs to be replaced. I also do need to replace the CV's, control arms to name a few, and the truck is pretty badly rusted + the engine is knocking a bit, so who knows how much time is left for her. I think 3-4 years max if I'm being optimistic. So investing $5-6k into AHC components might not be the best idea to do with this exact truck.

Thank you for your questions and help!
 
If you change the rear springs in a AHC vehicle do you have to put the same orginal ones or can you go stock 100 series suspension ome series one's.
 
If you change the rear springs in a AHC vehicle do you have to put the same orginal ones or can you go stock 100 series suspension ome series one's.
Stick to OEM if you don’t have any added weight like drawers or a fridge.
 
View attachment 2018163

Update to my risky decision installing 80 series Dobinson springs in the back (standard height spring) on sensor lifted LX470. Driven 10k miles now.

The springs have taken a good amount of driving to settle and get to the same comfort levels that I am used to having. After a 300lb combined weight of of a Dissent rear bumper and spare tire, I still have amazing comfort with full AHC capabilities. Took a pressure reading and was excited to see how capable this setup can be in the future. 06 LX has nearly 200k miles, rear shocks replaced at 150k, all Globes and accumulator as well as front shocks are still original. 13 ticks on the graduation level.
View attachment 2018169

4.1 MPa-g! The shocks start to shut off partially at around half a tank of fuel, but the dampers continue give a good ride. Once filled up there is no problem. Its ready to take anything I throw in it!
Would you have any system issues driving with rear pressures being lower then spec? Still driving ok? Thanks
 
Hey @PADDO ,

Random question that i couldn't find by searching.

Is it worth changing LX470 torsion bars since many mention sometimes rear springs aren't enough? or spacers are always the best case due to cost? If you are dead set on remaining stock is adding spacer + replacing rear springs the same performance as the more costly option of torsion bars + rear springs?

Thanks! apologies for the noob question in advance.
 
Hey @PADDO ,

Random question that i couldn't find by searching.

Is it worth changing LX470 torsion bars since many mention sometimes rear springs aren't enough? or spacers are always the best case due to cost? If you are dead set on remaining stock is adding spacer + replacing rear springs the same performance as the more costly option of torsion bars + rear springs?

Thanks! apologies for the noob question in advance.
I'm not @PADDO but I went down this road when I was baselining my 100. It's all about pressure. You can add weight to a AHC 100 but keep the pressures in the correct range. You can use LC torsion bars with AHC if you add too much weight to the front of the 100 to get the pressures in spec. I needed a rear spacer to get my rear's in spec (along with new OEM AHC springs). The aftermarket yellow King AHC springs are also an alternative but might be too stiff (which is too low of pressure) if you don't have enough added weight in the rear like a metal bumper or drawer system. If you have LC torsion bars and King AHC springs and your pressures are now too low, you can sensor lift the 100 some to get the pressures up, haha.
 
My nagging "issue" with AHC is wondering if the suspension doesn't feel quite right. I feel bumps pretty well and I subjectively recall an older 100 series land cruiser standard suspension feeling like being on a cloud vs the small cracks in the road. The question is driving me insane when I'm on the road..

I've read what seems like every AHC topic on here over the past few months before and after my LX470 purchase. Knowledge is there but spread around.

I'd like to replace the major AHC wear items short of the globes and it would be very useful to confirm these steps in one post, for myself and others as well wondering about their suspension.

Here's what I've come up with for the most bang for the buck: please let me know if you'd add or remove anything / change ordering, etc. For the record, my LX is at 117k miles.


First you would want to diagnose if you have a problem with your AHC.
Unfortunately, the only test I know of is to check if your globes are bad via the "Height Test".
I have no way of knowing whether the other components are bad or if my ride is standard / okay. I just have a gut feeling that it can be improved. At worse, you'll be extending the life of your AHC by reducing wear on it.



AHC height test.
Put vehicle in LOW. Mark fluid level in AHC reservoir.
Put vehicle in HIGH.
Number of graduations (ticks) on the reservoir from LO to HI should be at least 7. If less, your globes are shot and it's very expensive to replace.

I personally get 14 or so so it appears they are in great condition.



Assuming those globes are fine, it's time to start working:



Flush AHC fluid.
AHC Fluid Change How To -- Need Input

Cost: $40 / can. Need 2.
Dealer charge around $200-250.
Difficulty: Easy.

Result: Many report increased ride quality. I didn't notice so much when the dealer did it. I am going to buy 2 cans and flush it till it's clean.




Test neutral pressure / crank torsion bars accordingly
Neutral pressure is the pressure of the AHC system at each wheel in the N position. The AHC system is designed to carry a certain load while the torsion bars in the front / coils in the rear pick up the rest.

My dealer refuses to check the neutral pressure for me saying it's only what crazy enthusiasts do so I've found a product called the Tactrix Open Port 2.0 which can read the pressures.

Once you have the pressures up front, you'll be able to crank the torsion bars until the AHC system is carrying the correct load. Others blindly do 3-6 cranks every 5 years.

Here's a post from somebody who cranked Tbars based on neutral pressure data: Measure AHC neutral pressure?

Cost: $100-200 used/new for Tactrix Open Port 2.0 Cable There's a $35 alternative discussed below; waiting for reports.
Cost at dealer: they cowardly refuse.
Result: Haven't done it yet. Hopefully noticeable.




Replace Rear Coil Springs
The neutral pressure test will probably show the rear AHC pressures too high due to age of the rear coils.

Posts on mud suggest 5 years max before rear AHC starts going over spec on load.

Anything else in this rear suspension setup I should replace?

Part numbers:
48231-6A730
48231-6A740

Cost: ~$200 for parts.
Cost at dealer / mechanic: ?
Result: haven't done it yet.




My hope is that after these changes I'll have done as much as I can (without spending too much) for my ride.

Any comments, additions, etc. appreciated.
Hi Yuji!

Thank you for posting all of this!

Can you confirm whether cranking the torsion bars, replacing the springs, and flushing the AHC fluid did in fact fix your ride quality?

I am contemplating the same thing right now
 
I have just replaced the globes on my 2002. It has 142k miles, not a whole lot, but it wasn't maintained as diligently by PO as my other one with nearly double that mileage. I drain the AHC fluid at the same time I do that with the brake fluid. And as with the brake fluid you have to be super attentive. Many a time I had to drain 'just a bit more' from the opposite side of the initial drain, sometimes all four or even five drain valves to release the tiny spec of gas trapped there. What I noticed over the years that even the slightest variation in the floor level of the garage can bring a tiny bubble in this or that corner of the closed contour. Think of it as a carpenter's bubble level. I haven't approached torsion bars, springs, bushings yet. I haven't even looked at the pressure numbers, but the ride is heavenly now after all the consecutive corrective micro-bleeds. I do this with every AHC fluid service. The fluid essentially works every time, it is always on, like the brake fluid, just the frequencies and amplitudes differ.
 
Last edited:
Alright, got through all 30 pages. I have a much better understanding of the system but I could still use some advice with my truck. I picked up a 2003 LX with 148k miles. It has been in southeast Virginia its whole life and has very little rust. The AHC will go to L and N without an issue. When I select H it will blink a few times and then N will be lit solid. When the truck is in N the center cap to fender height is 21" all around. I got techstream working earlier and my pressures are all too high. My understanding of what I need to do is as follows:

  1. Check the globes by measuring the change in fluid level when going from L to N.
  2. Flush the system with new suspension fluid.
  3. Adjust height sensors to bring the front down to 19.75".
  4. Crank on the torsion bars to get the pressures down and reindex the torsion bars as necessary.
  5. Order either King or OEM + 30mm spacers for the rear.
Does my plan sound reasonable?
Would the pressures being off or sensors being maladjusted prevent it from getting into H?
Why does the passenger side height sensor seem to lag so much?

N.png


Lo.png


H(N).png


N(2).png
 
Last edited:
What do the different readings you posted represent.
The pressure readings should be read only when going from L to N.
 
The photo with the filename n is the neutral pressure. I also showed the numbers in high and low to show what the height sensors were reading.
 

Users who are viewing this thread

Back
Top Bottom