AHC Musings

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7schulz

7schulz

10 Year 15 Year
Joined
Dec 9, 2008
Threads
223
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2,664
Location
Zionsville, IN
So I recently picked up a 2002 LX470, excellent condition and dealer maintained etc. As being OCD I went to work replacing lots of stuff and last weekend replaced the AHC fluid because it was probably time. I didn't have any ride issues and the AHC worked perfectly.

Now that I replaced the fluid with the new Toyota/Lexus fluid, Pt. # 08886-01805with a slight red tint, my ride has noticeably gotten stiffer. After reading several AHC threads people talked about much better it rides after replacing the fluid/and replacing the fluid because there ride was harsh.

Picture the comfort/sport dial. Comfort setting was quite bouncy (think old Cadillac) and the sport was pretty firm but not too jarring. It is a Lexus after all. Now after I changed out the fluid, it has shifted to a more firm ride it all settings, so picture throwing out the two comfort settings and shifting all 4 dots over, where sport it very firm and extremely flat through round-a-bouts and a little jarring and comfort has nice ride but less bounce and sway. I have full travel up and down and it covers the normal amount of gradients on the reservoir jug.

For all of you with AHC is this normal?
 
Sounds normal, you went from bouncy and sloppy to comfortable and firm so that's not a bad thing. My own experience is new fluid with associated bleeding relieves harshness and jarring, maybe your system had a fair bit of air in it which contributed to the bouncy characteristic. Neutral pressures need to be checked too, being an 02 it's pretty safe to say your pressures will be on the high side of spec, I installed 10mm spacers in the rear and cranked the TBs 2 3/4 turns and got everything spot on and it rides nicely.

Sent from my iPhone using IH8MUD
 
If the ride is bouncy/underdamped, it is likely one or more of your accumulators have gone "flat" as in the nitrogen and AHC fluid are no longer separated by a layer of rubber. You can try to isolate which one has gone flat by driving off fairly high curbs one wheel at a time but it might still not be clear.

Maybe it could be air in the system? Personally, I'd try and bleed it again and check for air bubbles. If the problem turned out to be a flat accumulator(s) and I couldn't source any for cheap, I'd scrap the AHC.
 
No it is much more dampened and not bouncy at all now. I was just confused because all the threads I read said people had rough rides then they bled the system and it got smoother. Maybe I'm just used to really old stock springs and shocks with 180K miles on them in my previous LX450. It's probably perfect for you all, I just like not feeling anything from the road. Total Isolation.
 
To me, "comfort" mode can be described as "floating," as in very isolated... and cadillac-like. I know the ride is very subjective but since you LX is still stock(?), maybe you can compare to somebody else's.
 
Yes the full comfort setting now is pretty much that way, Isolated, with just a bit of extra sway and sport is very sporty. Hey maybe it's just working perfectly normal and I've never driven one when it was new. Before the fluid change I used the setting one click away from sport and it was very comfortable and isolated where as comfort mode was too bouncy and almost made me car sick.
 
Another question, anyone set the AHC to low and turn off the AHC so it stays low, is this and or leaving it in the high mode bad for the system. I'm thinking lower profile will help with aerodynamics and mpg why on the highway.
 
Sounds plausible. If you had air in the system, the damping force actuators don't do their job too well. Now, that you've gotten rid of the air bubbles, it is working as it should?

The "off" button won't keep it in LO. It's purpose is so that when you hook up or detach a trailer, the AHC won't change the height. More of a matter of safety. It's not a good idea to keep the AHC on LO at highway speed. The system will automatically revert to N mode at ~18mph.
 
7schulz said:
Another question, anyone set the AHC to low and turn off the AHC so it stays low, is this and or leaving it in the high mode bad for the system. I'm thinking lower profile will help with aerodynamics and mpg why on the highway.
Click to expand...

Slee sells an override to set and lock AHC in high. Perhaps an override can be created for locking in low, would be great on long smooth highway runs.
 
Doesn't the owners manual state that driving the vehicle in Lo can cause damage and/or be dangerous...?
 
The system always reverts to normal height if/when you exceed 19 mph, you can't "leave it in low" or "leave it in high". Please grab your manual and check it out, or place it in high and go for a drive, put it in low and go for a drive, whatever, it will revert back to N at when you hit 19mph.

Sent from my iPhone using IH8MUD
 
artwerks said:
Doesn't the owners manual state that driving the vehicle in Lo can cause damage and/or be dangerous...?
Click to expand...
Per earlier posts here, the 'Lo' setting gives you virtually no shock damping...I use it for under hood stuff that may take a while, and getting mil in and out of truck.

Steve
 
7schulz said:
I know that if you leave it on high it can wear out the system faster because the springs take less weight and the AHC takes more.
Click to expand...

I'm not sure if this would work, but I've considered it:
What if you what if you put in the stronger torsion bars a d the 2" lift rear springs with the AHC.
Would the AHC still be able to go into N and Lo?


PADDO said:
The system always reverts to normal height if/when you exceed 19 mph, you can't "leave it in low" or "leave it in high". ..
Click to expand...

You can, actually.
Slee makes a circuit board with a switch you can add that allows you to override the function you speak of so that it will remain in Hi at all times when the switch is activated.
 
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