Definitive list of AHC maintenance items (2 Viewers)

[Actualeyes]

I turned the TB 5 turns and this is the result. ... Front Pressure Sensor 7.5 Mpa-g Rear Pressure Sensor 7.2 Mpa-g Accumulator Press Sensor 10.3 Mpa-g Almost there with the front.

You can keep turning until you either get fronts in spec or have to reindex.

The ride usually becomes noticeably better!

 

[Wilsil]

What's the maximum number of turns you can do?

 

[OregonLC]

What's the maximum number of turns you can do?

If you run out of threads you'd just need to re-index the bar. However at that point I might become suspicious of the strength of the material.

 

[dealmaker]

Sorry for the noob question, but what is re-indexing the bar?

If you run out of threads you'd just need to re-index the bar. However at that point I might become suspicious of the strength of the material.

 

[OregonLC]

The torsion bars have splines at each end. If you completely release the tension, you can slide the torsion bar to the rear, away from the LCA bracket. Then turn it one or two splines opposite the direction the bolt applies torque and push it back in. You will have 're-indexed' the starting point and therefore have bought yourself more adjustment.

Edit: Great pic set and descriptions here: http://sleeoffroad.com/installation/UZJ100_Suspension_Install.pdf

 

[Actualeyes]

If you run out of threads you'd just need to re-index the bar. However at that point I might become suspicious of the strength of the material.

Yes, clearly at some point you may need to upgrade your torsion bar (which after all is a spring)... but reindexing is a standard thing, and I've never seen Toyota specify when to worry that the capacity of your spring is a problem.

Presumably the front AHC dampers support perhaps 600kg and the torsion bars the rest, and they look similarly small diameter compared to the non-AHC bars as the rear coils look small diameter compared to the non-AHC coils.

 

[mskerman]

Mini VCI Success on AU 98' LX470

Just a heads up for the AU owners out there, I just received my aftermarket MiniVCI and loaded the Techstream cracked.
It will read AHC pressures and lots of other things.
The only limitation I have found so far is that the user configurable options are mostly not available. In fact the only option that I can access and change is the one to enable/disable Steering wheel retraction with key insertion.
I really wanted to enable all 4 door unlock, but when I click on that section, no options are displayed. The same occurs when I go into all the other user configurable options.
If anyone has managed to change the door lock feature on a 98 AU LX470, I'd like to know how.

 

[hdj 100]

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.
https://forum.ih8mud.com/100-series-cruisers/438560-ahc-fluid-change-how-need-input.html#post6127557

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: https://forum.ih8mud.com/100-series-cruisers/529309-measure-ahc-neutral-pressure.html

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, what do you mean with ticks concerning the height test. Do you mean Millimeters (ther´s no scale on my Reservoir) ?

thanks hdj 100

 

[uHu]

Hi, what do you mean with ticks concerning the height test. Do you mean Millimeters (ther´s no scale on my Reservoir) ?

thanks hdj 100

On the front port side corner of the reservoir, there are small horisontal lines embedded in the plastic.

 

[Actualeyes]

Just a heads up for the AU owners out there, I just received my aftermarket MiniVCI and loaded the Techstream cracked.
It will read AHC pressures and lots of other things... I really wanted to enable all 4 door unlock, but when I click on that section, no options are displayed. The same occurs when I go into all the other user configurable options.
If anyone has managed to change the door lock feature on a 98 AU LX470, I'd like to know how.

(a little off topic) Mine is 2003 and it works fine with Techstream/MiniVCI. Have you specified the Australian region when starting up techstream (and Australian crack code)? It does seem a bit strange to me that yours doesn't. I too have turned off the steering wheel retraction, changed to the simple door lock/unlock and perhaps other things I forget.

It is a pity you can't specify to the ECU how much fuel you have on board, tyre diameters for speedo correcting, L/N/H heights for AHC, show the real engine temp rather than the cooked results etc etc - are you listening Akio Toyoda? Yes, I know the answer to that dumb question. Stupid of me to ask really! That would be too logical.

 

[Wilsil]

There is no Australian code in my package, only 4 others, General, Europe, Japan and American from memory.
The only thing I can change is the steering wheel and I don't as I like it. But the doors would be very handy.

 

[hkeller]

Ok. Replaced all 4 control valve actuator accumulator and cranked the torsion bars 3 times; I cranked them three times a few years ago. The truck is a 2000. I still have almost no upward travel in the front. Thoughts?

 

[kgrove]

A bit of a thread jack, but pretty close to the target. Lets say I flush the AHC fluid, tweak the torsion bars, everything mentioned in this thread EXCEPT for replacing the globes. Are there other components in the suspension system - bushings, fittings, etc. - that could cause a harsh ride before I spend a boat load of money replacing the globes?

My specific problem is that my ride appears more harsh than I remember it. I've done the tests I can (drop test, AHC height test) without spending much on computer attachments I don't know how to use and everything is telling me the globes appear to be marginal.

Related note - when I switch from L to H the AHC fluid pump sometimes squeals or groans. Any idea what this could be?

I hate this damn AHC. It's more complication than it is worth.

 

[Actualeyes]

Ok. Replaced all 4 control valve actuator accumulator and cranked the torsion bars 3 times; I cranked them three times a few years ago. The truck is a 2000. I still have almost no upward travel in the front. Thoughts?

A bit of a thread jack, but pretty close to the target. Lets say I flush the AHC fluid, tweak the torsion bars, everything mentioned in this thread EXCEPT for replacing the globes. Are there other components in the suspension system - bushings, fittings, etc. - that could cause a harsh ride before I spend a boat load of money replacing the globes?

My specific problem is that my ride appears more harsh than I remember it. I've done the tests I can (drop test, AHC height test) without spending much on computer attachments I don't know how to use and everything is telling me the globes appear to be marginal.

Related note - when I switch from L to H the AHC fluid pump sometimes squeals or groans. Any idea what this could be?

I hate this damn AHC. It's more complication than it is worth.

Gentlemen, what be your neutral pressures? No point replacing globes if you don't know your neutral pressures.

It doesn't matter how many times you adjust your torsion bars, if the neutral pressures aren't in spec you will have a poor ride - no point blaming the spheres, replacing valves etc., until you have the neutral pressures in spec. Unless you have specific DTC codes.

If they're not in spec at the front, you need to ratchet up the torsion bars until they are. Without measuring the pressure, you're working blind and curse AHC all you like, you are just making hard work for yourself. If you don't want to spend the $35 for MiniVCI and software or don't want the bother of using it (it is quite easy), get the local LX or Toyota stealer to check it.

If they're not in spec in the rear there are inexpensive things you can do to fix that too, depending on what load you are carrying/intend to carry.

The AHC pump can get noisy, and it can fail. It can also be repaired. It's a pump after all. But if it is raising and lowering then mostly it's working and until the pump stops working, don't sweat it.

 

[SWUtah]

Ok. Replaced all 4 control valve actuator accumulator and cranked the torsion bars 3 times; I cranked them three times a few years ago. The truck is a 2000. I still have almost no upward travel in the front. Thoughts?

OME replacement? Worked for me

 

[Actualeyes]

OME replacement? Worked for me

OME replacement is for the intellectually lazy or intellectually challenged

But of course it works.

 

[uHu]

Gentlemen, what be your neutral pressures? No point replacing globes if you don't know your neutral pressure.....

Adding: And the height.
The lifting height, weight, and condition of steel springs, determines the pressure. So, by measuring the pressure and the height, and knowing if you have any extra weight, you know the condition of the steel springs (and as said here: fronts can be adjusted, rears can be changed or helped).

 

[hkeller]

Gentlemen, what be your neutral pressures? No point replacing globes if you don't know your neutral pressures.

It doesn't matter how many times you adjust your torsion bars, if the neutral pressures aren't in spec you will have a poor ride - no point blaming the spheres, replacing valves etc., until you have the neutral pressures in spec. Unless you have specific DTC codes.

If they're not in spec at the front, you need to ratchet up the torsion bars until they are. Without measuring the pressure, you're working blind and curse AHC all you like, you are just making hard work for yourself. If you don't want to spend the $35 for MiniVCI and software or don't want the bother of using it (it is quite easy), get the local LX or Toyota stealer to check it.

If they're not in spec in the rear there are inexpensive things you can do to fix that too, depending on what load you are carrying/intend to carry.

The AHC pump can get noisy, and it can fail. It can also be repaired. It's a pump after all. But if it is raising and lowering then mostly it's working and until the pump stops working, don't sweat it.

I have the cable. I just can't get the software to run on my laptop. I need an older computer. The local Toyota dealer is like, "AHC, WTF is AHC . . . neutral pressure?!?!?" The closest Lexus dealer is 3 hours from here. They fixed it once and knew the system very well.

I had a two hour drive today and every small bump was jarring. I might try cranking the bars all the way and see whether that helps or not and go from there. I ordered the rear spring spacers. If cranking the T-bars helps the front, I'll throw the 10 mm spacers in the back and see what happens.

Any thoughts on that plan? Thanks,

 

[Wilsil]

You need Windows XP to run the program and follow the instructions in the video on the little CD.
You have to copy a file from the CD after you have installed the application on your laptop.
It worked first time for me, after copying this file over.

 

[mskerman]

AHC Adjustment success!

Well I had a spare hour yesterday, so I decided to try to get my neutral pressures back into spec.
(Using MiniVCI and TIS for readings..)
(98 Model AU LX 470 - 302,000km, had easy on road only life & full Lex service till I purchased @ 238,000km. Was in immaculate condition & still mostly is!)
(- All readings in Mpa-g taken just after changing AHC from L to N.)

Initial Readings F8.0, R8.5
Turned both Torsion Bars 6 turns
New Readings F7.4, R8.5
Turned both torsion bars another 3 turns (9 Total)
New Readings F6.7, R8.5
Very happy with front, moved on to rear..
Ideally, I need to replace springs, or insert packers - My guess is 20mm? - suggestions anyone..

Until I have a chance to do that, I thought I'd see what I could do with my airbags to temporarily assist with supporting the vehicle & bring pressures down.
(Airbags from Airbagman.com.au - coil-rite kit)

All above readings were done with 0 PSI in airbags.
Specs for airbags say they can operate at up to 30PSI and should have a min of 5 PSI to hold them in place .etc.

I pumped both sides up to 10 PSI
New readings F6.8, R 7.2
Pumped both sides up to 15 PSI
New readings F6.7, R 6.5
Very happy with both readings now!

That said, I don't believe it is a good idea to rely on the airbags long term as they are likely to make the ride bouncy, and support the vehicle less as the AHC/Springs lift. My plan is to buy packers ASAP and fit them. I think 20mm should give me at least a couple of years before I need to go the full expense of new springs.

By the way, I LOVE the AHC system and will do my best to keep it. Partially because I need to lower the vehicle every time I drive into my garage in order to fit. Also, because it is nice to jack it up in car parks as it reduces the chance of others damaging my paint .etc when it is higher. When I am off road, I can jack it up for that bit extra clearance, but I don't have the downside of a permanently raised vehicle & COG when cornering at speed. And finally, the ride is so good when the system is working properly.

I did replace the fluid as soon as I purchased the vehicle, and have bled thru a litre or so several times since just from a preventative maint perspective. Replacing the fluid is very cheap insurance against damage to other parts of the system!

The whole adjustment was done in under an hour. The TB 30mm bolts were relatively easy to turn with a 400mm socket bar, and the whole job was quite easy to do. Thanks very much to all the other posters here who have gone before and made the path easy for us newbies!