Definitive list of AHC maintenance items (1 Viewer)

[PADDO]

+0.1 and -0.1 is well within tolerance and is absolutely fine, chances of setting and maintaining 0.0 and 0.0 consistently is slim to non as you'll get very slight changes day to day in displacement due to temperature and a hot/cold system for example. I'd not touch the sensors at all. At 6.5 and 5.1 you may find you're a bit over sprung and under damped at that weight. Part of the fun, if you will, is adjusting pressures to weights and working out what's the best combination for you in any given circumstances. Don't forget your airlift bags are progressive springs and will fight back against your linear coils when you drop to low.

 

[taco47001]

+0.1 and -0.1 is well within tolerance and is absolutely fine, chances of setting and maintaining 0.0 and 0.0 consistently is slim to non as you'll get very slight changes day to day in displacement due to temperature and a hot/cold system for example. I'd not touch the sensors at all. At 6.5 and 5.1 you may find you're a bit over sprung and under damped at that weight. Part of the fun, if you will, is adjusting pressures to weights and working out what's the best combination for you in any given circumstances. Don't forget your airlift bags are progressive springs and will fight back against your linear coils when you drop to low.

Awesome, thanks. One thing I should have done I guess, since you mention the bags being a progressive spring, is deflate the bags to minimum PSI before testing my neutral pressures. I set the bags at 14psi but should have lowered them to 5 or so to get as much weight on the shocks as possible... hind sight I guess. For now it drives buttery smooth. Thanks again for your knowledge.

 

[beachbumin]

@PabloCruise I picked it up off amazon. Good reviews but snail slow shipping. I will update as soon as it gets in with details on install.

 

[PabloCruise]

@PabloCruise I picked it up off amazon. Good reviews but snail slow shipping. I will update as soon as it gets in with details on install.

Thank you my friend. I know I need to do this...

 

[sorich]

What should I be looking at if the left side of my '98 LX470 is about an inch lower than my right? I measured center of hub to wheel well. It's usually slightly under 1" lower on drivers front, and slightly more than 1" lower on drivers rear.

So far I've only replace AHC fluid. I was assuming that the problem was the rear springs and an overdue torsion bar adjustment, but before I ordered the springs I thought I'd check with you guys. Does that sound right? I started wondering because I thought the system should auto correct given that there are height sensors in play... someone steer me straight, please

Pressures with 3rd row removed an 1/2 tank of gas:

Front: 7.8
Rear: 6.7
Accumulator: 10.7

160k miles. Assume original springs as I just got this truck a month ago. Also, 8 notches on the AHC H-L tank test.

 

[uHu]

If you had read through all the 217 threads about the ahc in here, you would have learned that you have to tighten your driver side Torsion Bar.
The ahc doesn't do any L/R balancing. The pressure is always the same on left and right, when standing still and when driving straight. It does close the connection between left and right during cornering tho', to prevent a bit of lean.

 

[camino70]

I thought it would have been related to height sensors?

Adjusting the torsion bars would only change the pressure?

 

[Dannyboy lx470]

I tryed adjusting mine torshion bars sprayed them with wd 40 wouldn't move tight as anything I used a ring spanner.

 

[PADDO]

In the behemoth "definitive list of AHC maintenance items" thread search the term "cross level" or start reading from the last post backwards.
The TBs basically do two things - 1) mechanically set front side to side cross level by providing (or not) a balanced lifting force to augment the hydraulics and 2) affect pressures by adding/subtracting mechanical lift that ultimately determines how much work the hydraulics have to do to maintain N height. The outputs of the two front height sensors are feed into the ecu and processed into an error signal that determines the actual height, they do not act independently wrt height and don't influence any lean.

 

[sorich]

In the behemoth "definitive list of AHC maintenance items" thread search the term "cross level" or start reading from the last post backwards.
The TBs basically do two things - mechanically set front side to side cross level by providing (or not) a balanced lifting force to augment the hydraulics and affect pressures by adding/subtracting mechanical lift that determines how much work the hydraulics have to do to maintain N height. The outputs of the two front height sensors are feed into the ecu and processed into an error signal that determines the actual height, they do not act independently wrt height and don't influence any lean.

That's what I was looking for. Thanks!! I've read hundreds of pages about AHC at this point but am stilll learning (and forgetting) information as I go. I'm taking notes along the way though, so I appreciate you taking the time to answer.

 

[sorich]

Another point of potential searching failure is this: looking for a walk through on replacing rear springs. Is it as simple as jacking up the rear of the frame and compressing the springs and popping them out? Can I leave everything else alone? Thanks!!

 

[camino70]

Another point of potential searching failure is this: looking for a walk through on replacing rear springs. Is it as simple as jacking up the rear of the frame and compressing the springs and popping them out? Can I leave everything else alone? Thanks!!

Yeah, it's that easy. No need to disconnect anything.

 

[uHu]

Yeah, it's that easy. No need to disconnect anything.

Alternatively: Undo the bottom end of the shock, pull it off the bolt, lower the axle and pick the coil out. Probably faster than compressing springs. Just keep an eye on the lenght of the brake and breather hoses as you lower the axle (with a small jack).

 

[camino70]

Alternatively: Undo the bottom end of the shock, pull it off the bolt, lower the axle and pick the coil out. Probably faster than compressing springs. Just keep an eye on the lenght of the brake and breather hoses as you lower the axle (with a small jack).

I didn't have much luck with the shocks and still needed the compressor.
30mm spacers in, now 6.7 and 7.1.

 

[sorich]

I didn't have much luck with the shocks and still needed the compressor.
30mm spacers in, now 6.7 and 7.1.

After new oem springs and 30mm spacers? Wow.... do you have a lot of added weight? I would have hoped they would be a bit lower.

 

[camino70]

After new oem springs and 30mm spacers? Wow.... do you have a lot of added weight? I would have hoped they would be a bit lower.

new lexus springs and 30mm spacers. Full tank, third row in, maybe 40lbs of stuff (car seats and extra kids stuff all the way in the back). Several miles and several up/down cycles and it's at 6.7, 6.9 and 10.7.

 

[PADDO]

new lexus springs and 30mm spacers. Full tank, third row in, maybe 40lbs of stuff (car seats and extra kids stuff all the way in the back). Several miles and several up/down cycles and it's at 6.7, 6.9 and 10.7.

What are your front and rear heights? The rear 5.6-6.7 MPa range should fall between 20.25 and 20.5 inch hub center to fender bottom (as transposed from the proper FSM height measurement technique). Your height accumulator pressure is creeping up and I wonder if that's negatively influencing your rear reading? You'd have to stick a gauge on the rear to see what the real pressure is if you wanted to follow it up.

 

[sorich]

Well, a quick update to follow up on my previous posts....

After swapping AHC fluid, my pressures up front have been hovering around 7.8-8.1, and in rear they have been between 6.7-6.9. The left side of the truck has also been sagging by about 1/2 inch.

Tonight I spent some time working on my torsion bars up front in preparation for replacing my rear springs next week. After a lot of back and forth, I cross leveled and the adjusted for pressure. I was amazed to find that it took 9 turns on the driver side to cross level and normalize pressure. Now the truck is sitting at 19.25" in front and 20.25" in back, with pressures of 6.7 in front and 6.3 in back.

What a difference! The ride is much smoother now and just feels overall more stable and composed.

I'll be putting in the new springs next week, so we'll see if I end up having to back off on the torsion bars to keep pressures in range.

 

[Dannyboy lx470]

Well, a quick update to follow up on my previous posts....

After swapping AHC fluid, my pressures up front have been hovering around 7.8-8.1, and in rear they have been between 6.7-6.9. The left side of the truck has also been sagging by about 1/2 inch.

Tonight I spent some time working on my torsion bars up front in preparation for replacing my rear springs next week. After a lot of back and forth, I cross leveled and the adjusted for pressure. I was amazed to find that it took 9 turns on the driver side to cross level and normalize pressure. Now the truck is sitting at 19.25" in front and 20.25" in back, with pressures of 6.7 in front and 6.3 in back.

What a difference! The ride is much smoother now and just feels overall more stable and composed.

I'll be putting in the new springs next week, so we'll see if I end up having to back off on the torsion bars to keep pressures in range.

Thats good to hear.Just a question I cannot move my torsion bar bolts and I sprayed them to what did you use and how were yours? .

 

[sorich]

Thats good to hear.Just a question I cannot move my torsion bar bolts and I sprayed them to what did you use and how were yours? .

I sprayed them with PB blaster about 30 minutes before I began working on them. Pretty sure this is the first time these have been adjusted given the amount that was needed to get the system back in line.

When I went to start turning them, it wouldn't budge at all at first. So I jacked up the front, put some stands up just in case, and found it to be much easier. I didn't use a breaker bar or anything. Just a medium sized 1/2" ratchet. I did about 6 rounds or so of measuring and checking pressures in between. I found that after I started moving them, I didn't need to jack it up anymore and could adjust it just fine when the AHC was set to the High mode. I've heard of others needing to use breaker bars,but if you can lift the tires off the ground it should be pretty easy.