AHC sometimes stiff, sometimes soft

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GuazisMotos

GuazisMotos

Joined
Feb 13, 2026
Threads
1
Messages
9
Location
Chicago Illinois
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?
 
I'm in the same boat- I'm looking ro do a sensor lift just under 2". Looking to buy LC torsion bars and rear springs. The LX rear springs are like 25 mm and the LC are 29mm thick. I also hear that 80 series Front springs are good to swap out the LX rear( need someone to chime in on that)?
 
Why did you even add springs? Did you add more weight? Like significantly more permanently?
I'm planning to do the same in a few weeks but I am adding steel bumpers and sliders. (27mm torsions also)
And depending on the pressures also a 1" sensor lift.

All I can see is the awning and kayak/s in the avatar pic. No where near enough extra weight to need those springs.
Hopefully you can de-crank the torsions down enough to fix the pressures.
 
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x8o8drifter said:
Why did you even add springs? Did you add more weight? Like significantly more permanently?
I'm planning to do the same in a few weeks but I am adding steel bumpers and sliders. (27mm torsions also)
And depending on the pressures also a 1" sensor lift.

All I can see is the awning and kayak/s in the avatar pic. No where near enough extra weight to need those springs.
Hopefully you can de-crank the torsions down enough to fix the pressures.
Click to expand...
Original springs were tired and the rear pressure was reading at 7.9 prior to the King Springs. Reason I went with the Kings and not OEMs was because I haul a lot of stuff in the back frequently and I saw others on this forum install Kings with stock weight and not have issues in ride quality.

To clear things up, the ride quality greatly improved since I bought the truck after I changed the fluid, globes, and springs. I'm curious why its rough sometimes and other times it rides like butter with no change in weight.
 
GuazisMotos said:
Original springs were tired and the rear pressure was reading at 7.9 prior to the King Springs. Reason I went with the Kings and not OEMs was because I haul a lot of stuff in the back frequently and I saw others on this forum install Kings with stock weight and not have issues in ride quality.

To clear things up, the ride quality greatly improved since I bought the truck after I changed the fluid, globes, and springs. I'm curious why its rough sometimes and other times it rides like butter with no change in weight.
Click to expand...
Do you have an install guide to the globes install?
 
NolaNomad said:
Do you have an install guide to the globes install?
Click to expand...
I followed Geriatric Pearl's video on youtube. Pretty simple process and it's even easier if you don't have the side steps. I went ahead and bought a fan clutch wrench on Amazon (blue handle) and it worked for me on all 4 globes.

If you live where they put salt on the streets, spray the globes and bleeder screws with PB Blaster days in advance multiple times. The bleeders round off real easy so just take it slow.
 
GuazisMotos said:
I followed Geriatric Pearl's video on youtube. Pretty simple process and it's even easier if you don't have the side steps. I went ahead and bought a fan clutch wrench on Amazon (blue handle) and it worked for me on all 4 globes.

If you live where they put salt on the streets, spray the globes and bleeder screws with PB Blaster days in advance multiple times. The bleeders round off real easy so just take it slow.
Click to expand...
Nice👍🏻
 
NolaNomad said:
I'm in the same boat- I'm looking ro do a sensor lift just under 2". Looking to buy LC torsion bars and rear springs. The LX rear springs are like 25 mm and the LC are 29mm thick. I also hear that 80 series Front springs are good to swap out the LX rear( need someone to chime in on that)?
Click to expand...

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.
 
GTV said:
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.
Click to expand...
Well I have a cargo box platform, a rear tire carrier with full spare off the hitch and a Yakima rooftop box. I've been loaded up with tools lately and can feel the suspension is feeling rough
 
I eased of on the torsion bars 2 full turns so now pressures are reading Front: 6.5 and Rear: 5.2. I also did another round of bleeding at all 4 globes, saw a lot more air bubbles compared to the previous attempts. The ride got a lot better again. Will continue to update as ride changes and such.
 
NolaNomad said:
Well I have a cargo box platform, a rear tire carrier with full spare off the hitch and a Yakima rooftop box. I've been loaded up with tools lately and can feel the suspension is feeling rough
Click to expand...
I agree with GTV about not needing non-AHC springs since those were designed to carry the entire weight of the rear. If I remember correctly, AHC carries about 40% of the weight. I'd say go with the King Springs and add spacers if you need to if the current weight would be too much. Do you know what pressures you're currently reading at?
 
OP, please keep us posted if you figure it out. I have my front pressures dialed in at the midpoint of the range and the rears are ~1 bar higher vs midpoint (due for new springs since spacers won’t get me to where I need). My current globes are shot with only 4 gradations from lo to hi, but my experience is the same. Comfort to sport dial works. On comfort, some bumps I barely feel but I crash over narrow cracks on the road. Would be a real letdown if the new globes I have on the way from Impex don’t address that.

Edit: Could be the dampeners
AHC does large accumulator affect damping? - https://forum.ih8mud.com/threads/ahc-does-large-accumulator-affect-damping.793110/
 
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GuazisMotos said:
I agree with GTV about not needing non-AHC springs since those were designed to carry the entire weight of the rear. If I remember correctly, AHC carries about 40% of the weight. I'd say go with the King Springs and add spacers if you need to if the current weight would be too much. Do you know what pressures you're currently reading at?
Click to expand...
Ah, ok cool. I'm still needing to get Techstream loaded. I see the Kings are the sweet spot . Sensor lift target is 1.8 inch only I don't want to angle up the CV too much. Trying to stay away from a different drop as well ...but ya know
 
NolaNomad said:
Ah, ok cool. I'm still needing to get Techstream loaded. I see the Kings are the sweet spot . Sensor lift target is 1.8 inch only I don't want to angle up the CV too much. Trying to stay away from a different drop as well ...but ya know
Click to expand...

I’d personally do a diff drop with any lift. Increased angle wears CV’s faster and if you’ve priced out new ones you’ll see why you don’t want to get into a habit of replacing them.
 
GuazisMotos said:
... I'm curious why its rough sometimes and other times it rides like butter with no change in weight.
Click to expand...
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.
 
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