AHC sometimes stiff, sometimes soft

[GuazisMotos]

If the pressures, heights, bushings, globes, bleeding, etc are all ok, it might come down to the sensors.
The AHC ECU adjusts damping according to road conditions. Road condition is determined by the frequency and amplitude of changes in the signals from the height sensors. A worn sensor, or a loose or sticking sensor link arm, will give erratic signals from the height sensors.

Gotcha, could that be the reason why I find my rear adjusting itself while I'm parked sometimes?

 

[GTV]

Gotcha, could that be the reason why I find my rear adjusting itself while I'm parked sometimes?

The A in AHC is for Automatic. It self adjusts as needed. That’s normal behavior.

 

[NolaNomad]

Unless you are adding a LOT of weight do not use non AHC LC torsion bars or coils.
80 series front coils do not fit the rear of the 100 but the rear coils are interchangeable.
Kings coils are a good choice for 2" lift but will depend a lot on weight.

I'm picking up a pair of King KTRS-79 take offs this weekend for $200, I have a pair of LC torsion bars on the way ($200), and I found Slee LCA reinforcement brackets on ebay ($22) in hand. Will be doing the sensor lift next week

 

[GTV]

I'm picking up a pair of King KTRS-79 take offs this weekend for $200, I have a pair of LC torsion bars on the way ($200), and I found Slee LCA reinforcement brackets on ebay ($22) in hand. Will be doing the sensor lift next week

 

[GuazisMotos]

Just making a quick update: Still in the process of bleeding the system, gone through about 3 cans of the AHC fluid. The ride has been getting better and better after each bleed. Once I start to feel the suspension get a little rough again, I go back to bleeding and I will see more bubbles coming out, sometimes 2 or 3 small ones other times multiple big ones.

At this point, the fluid is starting to come out of the globes the same color it was going in instead of that super dark brown as well. Also, the amount of times I've had to bleed recently has decreased thankfully.

The King KTRS-79s are definitely a little firm, but obviously get soft once weight is added in the back of the vehicle. I'd say they were a pretty good choice!

 

[Tinkerer]

Hello everyone! I've had my 2006 lx470 currently with 228,700 miles for a little over a year. So far I have bled the AHC fluid, replaced the globes (Toyota OEM from Impex), and installed King KTRS-79 springs. I've also gone through YotaMD's AHC cheat sheet. Pressures are currently Front: 5.9 and Rear: 5.0.

Now here is my main issue. Sometimes, the ride quality will be that legendary riding on a carpet feel and other times I'll feel every single small bump on the road that will rattle the entire cabin. If I look at the hood while the ride is having an episode, I'll notice that the front is bouncing up and down like there isn't any dampening. The comfort to sport knob and the height adjustment both still work.

I would me inclined to replace the bushings but given that the issue happens sometimes makes me lean towards air/gunk in the system that is moving, allowing for change in ride quality. I'm currently bleeding the system little by little everyday after work and I will see some tiny air bubbles (maybe 1 or 2) come out from each globe.

Am I heading towards the right direction or should I be looking at replacing the shocks (I know the rear is a pain) and bushings?

"Sometimes, the ride quality will be that legendary riding on a carpet feel and other times I'll feel every single small bump on the road that will rattle the entire cabin."

This, and the depleted Accumulator globe$ at around 11 years with a need to replace them about every 10 years, was why I abandoned AHC.

You can read about all the costly complicated burden it imposes, to keep it going past 10 years.

Complicated systems with intermittent faults are vexatious time sinks, sometimes can't be fixed because the symptoms appear sporadically. Or maybe educated guesswork parts changing eventually replaces the faulty part, wasting much time and money in the process.

It's wonderful when new. Too costly in the long run - time, money, and aggravation.

One of the experiences that turned me into a staunch K.I.S.S. advocate.

 

[Gartenmeister]

Just making a quick update: Still in the process of bleeding the system, gone through about 3 cans of the AHC fluid. The ride has been getting better and better after each bleed.

Any more updates? I recently replaced my 26yr old globes and ride comfort is pretty much unchanged. It's OK but not great, still a little rough over small road imperfections. I was hoping for magic carpet. My pressures (6.4) and grads (14) are fine, comfort/sport knob works, height adjust works fine (if a bit jerky) and swaybar bushings/hardware are all fresh. Oh, coil springs as well, Land Cruiser AHC (brown/purple) version. Wondering if you got yours sorted out?

 

[uHu]

Any more updates? I recently replaced my 26yr old globes and ride comfort is pretty much unchanged. It's OK but not great, still a little rough over small road imperfections. I was hoping for magic carpet. My pressures (6.4) and grads (14) are fine, comfort/sport knob works, height adjust works fine (if a bit jerky) and swaybar bushings/hardware are all fresh. Oh, coil springs as well, Land Cruiser AHC (brown/purple) version. Wondering if you got yours sorted out?

Next thing to check is sensors and linkages. The damping is continually adjusted according to how the suspension moves, so if the ahc brain doesn't know exactly what the wheels are doing, it will not adjust the damping in the best way. Any slack or stickyness in the links or any dead spot on the sensor will give a bad ride. The sensors don't normally last any longer than the globes, they rather have a shorter life, depending on the environment. Non-OE sensors are generally useless.

 

[GuazisMotos]

Any more updates? I recently replaced my 26yr old globes and ride comfort is pretty much unchanged. It's OK but not great, still a little rough over small road imperfections. I was hoping for magic carpet. My pressures (6.4) and grads (14) are fine, comfort/sport knob works, height adjust works fine (if a bit jerky) and swaybar bushings/hardware are all fresh. Oh, coil springs as well, Land Cruiser AHC (brown/purple) version. Wondering if you got yours sorted out?

Actually destroyed my passenger CV-axle a couple of days after posting that last update at an offroad park

Since the last update, I've only bled the system a couple of more times and adjusted the front and rear sensors. I have the rear at a 1 inch sensor lift to increase the pressure since it was too low after installing the king springs, the truck has a slight rake now but it goes away with gear. Its not THE magic carpet feel, but it is for sure the most comfortable ride in my fleet.

I think at this point, I have gotten as far as I can in terms of ride quality with just messing with the AHC system. Next up is going to be bushings, balljoints, etc., but not in a rush.

I'd follow uHu regarding the sensor stuff too. I didn't replace any of mine, but the biggest difference was when I had those dialed in