AHC Sensor Adjustment for Lift

hoser

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Adjusting your AHC sensors are fairly easy :)banana: job). You'll need to furnish/fabricate a simple bracket extension which I'll cover in step 5. You'll also need one can of AHC fluid from Toyota $22/can. (part # 08886-01805). I have heard the exact fluid costs more if bought from Lexus.

1. Take measurements of your ride height at each corner of the vehicle. I recommend measuring from the fender lip to the bottom wheel lip.

2. Turn off ignition. Jack up the front, secure with a jack stands and remove your front wheels. Locate the Height Control Sensor as seen in the diagram. Note the position on the adjustable top mount. You are going to want to slide it up as far as possible in the next step.

3. I found it easiest to just remove the top nut of the heim joint (10mm) and adjust the rod so that it is as short as possible. This will give you about 2" of lift in the front. If you want 2.5", you'll have to shorten the heim joint (I used a cut-off wheel) and then used the existing stop-nuts to "smooth out the thread" and actually remove the stop nuts completely. Be careful because one side is a reverse thread. Not many people I know have a reverse cut tap/die set.

Once done, reinstall the heim joint and adjust it so that the Height Control Sensor lever is as high as possible. Remount the wheels. You can readust the sensor through the wheel-well later. Make sure ALL adjustments are done while the vehicle is OFF for safety reasons!

4. After the front sensor adjustments are done and all jacks are cleared away, you can start the engine. All the doors, hatch and hood need to be closed for the AHC to work. This adjustment will yield up to 2.5" of lift in the front.

5. Now for adjusting the rear. Again, make sure ignition is off. No need to remove the wheels, just crawl underneath and locate the Height Control Sensor. There is only one for the rear. If you slide the adjustment to the top, you'll gain about 1.75" of lift. For more, you'll have to extend the mount 2" or so. I used 1" aluminum flat stock and drilled two holes (to mount to the existing bracket) and slotted a 3rd hole for adjustability. If you space out the aluminum stock from the old bracket 3/16" of so, you can get better adjustability.

6. Fill Reservoir with AHC Fluid to correct level. It is also a good time to flush the system if its never been done before. Lexus recommends a flush every 60k miles. How to flush AHC fluid thread: https://forum.ih8mud.com/showthread.php?t=60619

After you get the height you want, you'll want to get an alignment job. If you haven't already installed a differential drop bracket, now is a good time.

About AHC HI/N/LO modes: if you raise the front 2", you'll still be able to go into HI mode. If you raise the front suspension 2.5", the AHC system will raise and then come back down to N mode. I suspect the suspension is "topping-out" and so it reverts back to N mode. However, you'll be able to adjust to LO mode at any lift height.

I noticed a slight increase in ride firmness. I'm not sure if it is because the increased angle of the A-arms or the increase in AHC fluid suspending the vehicle or if it's just all in my head. But the Ride Comfort adustments work fine after this mod. :beer:

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Edit: Perhaps more important than the amount of lift is the amount of droop left in the suspension. If you lift too much, your suspension (shocks) will "knock" (top-out) when going over bumps. Here's some advice from ATS4X4:

You should maintain a minimum of 70mm [2.75"] of droop in the 100 IFS front set up, if you have a Slee diff drop fitted, to stop the cv boots wearing out. [boot pleats shouldnt be touching in straight ahead position at ride height]. This is normally 50-60mm higher than standard, depending on accessory levels. On a 16" rim this makes for 770mm [30.3"] measurenent from bottom of rim bead edge up through centre of wheel to fender edge when set up correctly. Rear should be aprox 790-800mm [31.5"]
00000001AHC2AHC3.JPG
 
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CTapia

 
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Hoser,

This is great info! Sure looks to be quick and easy mod. Perhaps you can update this thread as you fine tune the system.
 

tabraha

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Maybe there would be an opportunity for an aftermarket kit to allow the re-adjusted high mode (4" lift) to work at an improved geometry for the suspension. That would be awesome. Diff drop would be a help for sure but would anything else be needed? That'd take the strain off the CV's right? Man, my brain is stewing with what could be done w/ 4" lift.

You really had a measured difference of 4" on high after this mod?
 

shocker

 
 
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I'd imagine that with the diff drop bracket, you could still use the "high" setting to get over more extreme obstacles that would require it.... it'd be no different than running a 2" lift without the drop bracket.

Both the 'high' and 'low' settings would still revert to 'normal' above 20mph, so any bad angles on the CV's at highway speed would be a moot point.

This sounds like a nice, simple job. Thanks for the write up!
 

hoser

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tabraha said:
Maybe there would be an opportunity for an aftermarket kit to allow the re-adjusted high mode (4" lift) to work at an improved geometry for the suspension. That would be awesome. Diff drop would be a help for sure but would anything else be needed? That'd take the strain off the CV's right? Man, my brain is stewing with what could be done w/ 4" lift.

You really had a measured difference of 4" on high after this mod?
I just measured, in High mode and in the front, I am getting about 3.5" higher than stock. But you could set-it to whatever you want--or however soon you want to change the CV's. I'm not going to ever run it in that mode. Too costly. Could take a few poser shots though. :D

Higher lifts will eventually come but they'll probably involve longer A-arms and CV shafts. There are some IFS Tundras with 5-6" lift (no body lift) nowadays.
 
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tabraha

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I was just thinking a diff drop would fix the CV vulnerability. Is that not correct?
 

hoser

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Sure it helps but the drop bracket lowers the diff by only 20mm. When you go to High mode, it raises it 1.7" inches or so... roughly twice the height of the bracket.
 

shocker

 
 
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I think I would equate using the "high" mode on this modified setup to the "extreme traction" mode the new Rover LR3's have, where in situations that none of the wheels are getting traction, they extend the suspension a little bit further just for a bit.

In other words, I wouldn't think it would hurt the joints too much if you put it on "high" just to get over a single obstacle.
 

hoser

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Yeah, probably wouldn't hurt too much. But keep in mind that there is an extra high mode as well. Supposedly it goes into extra high mode when in 4Lo and losing traction.
 

hoser

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It is for all years with AHC.

"Switching to high mode also increases the angle of approach from 30 to 32 degrees and the angle of departure from 23 to 26 degrees to help the LX 470 "step over" obstacles. The vehicle will go into "extra high" mode if it is in low range and traveling over rough terrain, with the height rising automatically by 1.2 inches at the front and approximately 1.8 inches in the rear."
 

tabraha

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Nah, I'm not talking about the current diff drop bracket. I'm saying that the full 4" potential of this simple mod could be achieved through a new design on the diff drop bracket. I agree 20mm isn't gonna take enough stress off of the CV's to put my mind at ease either. But what if someone came up with a new bracket that was made for this application?

I'm just thinking that this could be a really great mod that has little downside (it seems to already be a great mod). Easily allowing over 35"+ tires and full articulation while maintaining correct suspension geometry (with a redesigned DD bracket). All of this being achieved by the addition of a new DD bracket. It's just unheard of to have the opportunity to achieve something like this with just one part and some handiwork!

As far as the extra-high mode, if it's not user selectable then you can't count on it in my book. I'd hate for it to decide I didn't need that extra amount and then drop me down on something.
 

hoser

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What I meant by my comment about the extra-high mode is that with 3.5" of lift in the front, the suspension might automatically go into extra-high mode and try to add another 1.2"

But it can't physically do that. The suspension will top out.... and revert "N" mode.
 
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tabraha

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Yeah, I see what you were saying now. If we can get a redesigned bracket though, it'd be no worse than it is now. Man that would be so sweet. I just wonder if it's possible. I guess I need to start thinking about readjusting my sensors first. Of course, if I don't buy some sliders before that, my wifes family won't even be able to get into the thing!
 

tabraha

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Crap. That rains on my parade! Oh well good to know though; thanks Christo. I assume that would mean to get proper geometry up front a new suspension kit fabrication would be nece$$$$$ary for that much lift.
 

hickok

 
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After laying under the LX for about 2 hours checking out AHC, I thought of something that may work and wanted to bounce it off other heads.

In Fourwheeler magazine, they have GX470 (TraiLex) that they modified the front coil-overs and added a 3" "extention" to lift the truck without swapping for new coil-overs. My questions is, could you do the same with the LX470? Modify or extend the mounting points of the hydraulic shocks to lift the truck? I would go 3", but an 1 1/2" would work with a little adjustment of the sensors as well.

whatchyathink?
 
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Jim_Chow

 
 
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hickok said:
After laying under the LX for about 2 hours checking out AHC, I thought of something that may work and wanted to bounce it off other heads.

In Fourwheeler magazine, they have GX470 (TraiLex) that they modified the front coil-overs and added a 3" "extention" to lift the truck without swapping for new coil-overs. My questions is, could you do the same with the LX470? Modify or extend the mounting points of the hydraulic shocks to lift the truck? I would go 3", but an 1 1/2" would work with a little adjustment of the sensors as well.

whatchyathink?
I've seen brackets (alluded to in a previous thread) that are used in conjuction with a lift. One lift I saw on a LX (LC Cygnus) was 6"...they replaced the lower A-arms up front, front diff bolted below the crossmember w/ a thick spacer, front coil springs added (not sure if they ditched the t-bars altogether or not). The A-arms for the kit had new mounting points for the shocks.

--Jim
 
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