AHC practicality questions

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RockDriver

Joined
Sep 22, 2024
Threads
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Location
Northern Europe
I've seen lots of lamenting about just how expensive AHC repair is, so I went to browse the genuine (I think) AHC parts catalogue expecting to find the reason there. There's nothing that I could find that costs like 5 figures, not even 4 figures there. So what's the catch? Is the repair process itself complicated, specific knowledge, experience, equipment, tools required? Something else?

Personally I'm not an overlander worried about getting stuck while crossing the Siberia or whatever, so the fact that AHC is obviously less reliable than the conventional springs and shocks is not a factor for me.

I'd like to find and buy an HDJ100 with a working AHC. I don't know, is that realistic?
 
The internet strikes again. It's not that AHC is inherently unreliable or expensive, there's no "fact" there. This urban lore comes from years of little outside tech service knowledge and the solution of just replace it all with conventional springs and shocks. The info on Mud alone combined with Techstream access should allow anyone to service or replace their AHC short of it being completed rusted out.
 
RockDriver said:
I've seen lots of lamenting about just how expensive AHC repair is, so I went to browse the genuine (I think) AHC parts catalogue expecting to find the reason there. There's nothing that I could find that costs like 5 figures, not even 4 figures there. So what's the catch? Is the repair process itself complicated, specific knowledge, experience, equipment, tools required? Something else?

Personally I'm not an overlander worried about getting stuck while crossing the Siberia or whatever, so the fact that AHC is obviously less reliable than the conventional springs and shocks is not a factor for me.

I'd like to find and buy an HDJ100 with a working AHC. I don't know, is that realistic?
Click to expand...
This was me 2 weeks ago!

Recently, I purchased a dealer maintained 02 LX470 180k miles (East Coast) with a somewhat working AHC. It goes into all 3 heights LNH but the ride quality is ehh. I don't have any prior experience with the AHC but it feels harsh with some clunking noise coming from undercarriage while driving & shifting from Parking to Drive or Reverse. I got around 5.5 points when I performed the manual/visual AHC Fluid level test.

After a few hours of video research and reading here on the forums, I plan to work on these parts myself in an attempt to mechanically refresh and keep the AHC system.

Replace all 4 accumulators ~$1000
Replace both differential support assemblies ~$400
Replace differential stoppers (2 pc) ~$100
Replace front differential Mount/Cushion ~$100
AHC Fluid ~$100
 
srukh said:
This was me 2 weeks ago!

Recently, I purchased a dealer maintained 02 LX470 180k miles (East Coast) with a somewhat working AHC. It goes into all 3 heights LNH but the ride quality is ehh. I don't have any prior experience with the AHC but it feels harsh with some clunking noise coming from undercarriage while driving & shifting from Parking to Drive or Reverse. I got around 5.5 points when I performed the manual/visual AHC Fluid level test.

After a few hours of video research and reading here on the forums, I plan to work on these parts myself in an attempt to mechanically refresh and keep the AHC system.

Replace all 4 accumulators ~$1000
Replace both differential support assemblies ~$400
Replace differential stoppers (2 pc) ~$100
Replace front differential Mount/Cushion ~$100
AHC Fluid ~$100
Click to expand...
That sounds reasonable. So then I guess the main issue is that there are not too many LC AHC specialists out there and repair is probably labor intensive, that's why DIY is advised on this forum.

Do you anticipate being able to do this work by just jacking up each wheel separately? I was thinking that access without a proper ramp could potentially be a challenge.
 
I did it all and so can you. It isn’t hard if you do your reading.
Globes replacement and fluid flush is about as simple as working on a car gets. Brake pads are harder.

Getting TechStream working on a pc is the toughest part, but there is a thread on here that makes it very simple.
 
RockDriver said:
That sounds reasonable. So then I guess the main issue is that there are not too many LC AHC specialists out there and repair is probably labor intensive, that's why DIY is advised on this forum.

Do you anticipate being able to do this work by just jacking up each wheel separately? I was thinking that access without a proper ramp could potentially be a challenge.
Click to expand...
Correct, not many AHC specialists out there and parts will be mad expensive through them. I'd say it is medium level effort for DIY, if you can change oil, brake, etc then it should be fairly easy to work on. I'll be using just manual tools with a ramp, i do have tall jacks if needed but I think ramp will do better. Internet suggests that its good to have a buddy while you're doing this work.
I have ordered parts from IMEX japan to get best prices, dealership will charge almost double. You can also find a full set of accumulators on ebay for roughly around $750 these days, beware of aftermarket versions I think I saw a set for $400 but they were unbranded.

Hopefully, I won't need the TechStream but if I do, that'll be my biggest challenge as I have done no research on it and it is probably worth a few thousand dollars to buy one.

Attached below is a video to help you get started
 
What is the most common cause of AHC breaking down?

I have a potentially interesting case here saying that AHC is just broken, otherwise "kaput" in German:

I know that replacing the globes is not that big of a deal. What else? Could it be some burst line that is a pain to access? What's the most expensive and/or difficult to fix component if we're assuming worst case scenario?
 
RockDriver said:
...Could it be some burst line that is a pain to access?...
Click to expand...
That's it. Rusted pipes. Also corroded plugs on the wire harness hidden somewhere around rear left wheel well, that connect the ECU to the ahc valve body.
The most common faults are sensors, sensor linkages, sensor plugs, steel springs (coils and TBs) and globes; which are all easy.
 
RockDriver said:
I've seen lots of lamenting about just how expensive AHC repair is, so I went to browse the genuine (I think) AHC parts catalogue expecting to find the reason there. There's nothing that I could find that costs like 5 figures, not even 4 figures there. So what's the catch? Is the repair process itself complicated, specific knowledge, experience, equipment, tools required? Something else?

Personally I'm not an overlander worried about getting stuck while crossing the Siberia or whatever, so the fact that AHC is obviously less reliable than the conventional springs and shocks is not a factor for me.

I'd like to find and buy an HDJ100 with a working AHC. I don't know, is that realistic?
Click to expand...
Don't let forum paranoia steer you away from AHC, just a bunch of cry babies on here who want their vehicles to last to a million miles and never break down lol

You mentioned you aren't concerned with remote travel, most folks like the idea of a fail safe system like conventional suspension so they remove the AHC for that exact reason, fear of failure in remote areas.. Folks like @Moridinbg have had their fair share of bad luck with AHC while being far from home and still hasn't removed it yet

I don't know anything about the HDJ100 so I can't chime in on that. I thought AHC was only a LX thing.
 
I almost got stuck, while crossing Patagonia lol and I am not removing it.
The only expensive items that are likely to fail at some point are
  • Height sensors, they are a wear item - the contact patches inside wear out - ~$230 each, there are 3 of them
  • Spheres - also a wear item - the nitrogen inevitably leaks out with time. The membrane can get ruptured too - $150-350, various sources - Japan, eBay, etc, 4 on the car
I would say those should be fine for 400k km/250k miles, but that's not a guarantee at all, might be way more or way less just as well. The motor should surely be a wear item eventually, having brushes, but I am not aware of any failures yet.

The other known failure points:
  • Wiring - there are well known connectors in the rear of the frame that sometimes corrode. Wires can also get broken. Same applies for all other electricals - ABS, headlights, hitch wiring, etc.
  • Hydraulic lines - on very corroded trucks the hard lines can corrode and leak. Usually that only happens on trucks that are so corroded that you really should walk away anyway
  • Pump getting clogged - this seems to be a recently discovered rare issue that very well might have happened for years, without us knowing, but recently me and a few others tracked down persistent problems to blockage in the return valve
The ECU, valves and shocks are robust and very rarely fail.

It is pretty reliable system. Very versatile between Comfort and Sport mode.

@Mike NXP The HDJ100 in Europe has the VGRS as standard and AHC as standard. LX was never sold here.
 
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My truck has over 300k miles/480k km, no idea if the AHC fluid had ever been replaced as it was darker than anything I’d seen online when I flushed it, but it worked okay and never failed (did drop me into L once when I was overloaded) until I replaced the globes a short while back.

I spent around $600 on globes + fluid (and I still have a full tin of fluid left), and it drives like a completely different vehicle after replacing them.

However, my undercarriage is rust free. If you can find a 100 that’s very clean underneath, then your chances of having a working and maintainable AHC system will be much higher.
 
srukh said:
This was me 2 weeks ago!

Recently, I purchased a dealer maintained 02 LX470 180k miles (East Coast) with a somewhat working AHC. It goes into all 3 heights LNH but the ride quality is ehh. I don't have any prior experience with the AHC but it feels harsh with some clunking noise coming from undercarriage while driving & shifting from Parking to Drive or Reverse. I got around 5.5 points when I performed the manual/visual AHC Fluid level test.

After a few hours of video research and reading here on the forums, I plan to work on these parts myself in an attempt to mechanically refresh and keep the AHC system.

Replace all 4 accumulators ~$1000
Replace both differential support assemblies ~$400
Replace differential stoppers (2 pc) ~$100
Replace front differential Mount/Cushion ~$100
AHC Fluid ~$100
Click to expand...
Accumulators should be about 600…

Make sure to search places like impex for your needs.
 
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