I have regular lc springs on my lx. No issues at all. Stock height, slightly bigger and heavier tires. Look to further monitor and adjust your pressures imho. Have recently added skids and sliders, still all good here.
The ABCs of AHC - How to Measure, Flush, and Adjust all in one place
This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.
So you have regular LC TBs and rear springs? What pressures do you have all round and have you noticed much difference in the ride comfort?
- Thread starter
- #503
Yeah, go get yourself some OEM AHC TBs and OEM or King rear springs. Only a crazy loaded rig needs non-AHC TBs and springs plus the AHC itself.
Only rear springs, not torsion bars. It’s been quite a while since I’ve measured my pressures so I couldn’t tell you exactly but they were within normal spec. The biggest variable for ride comfort for me was the difference between passenger tires and e rated tire tires. E Rated tires are a rough ride.
@DubR
Howsitgoin with the suspension?
The whole idea with the AHC system on the 100 is that all the suspension damping is handled by the valves in the actuators, which then work the same way as normal shock absorbers. One prerequisite for this to work is that there is enough pressure on the ahc system and that the "shocks" are carrying enough weight to be able to control damping. The mass of the truck has to be shared between the 4 steel springs and the 4 nitrogen spheres for this to work. When you get enough pressure on the ahc fluid and the nitrogen spheres, you also get enough movement of the hydraulic fluid through the actuators to dampen the suspension movement. Without this, you get a jarring ride and a potentially dangerous road handling.
If you offload the ahc system by installing stiffer/stronger steel springs; the ahc valves, shocks and gas springs might not get enough pressure to work with; and that is what I believe has happened in your case.
For the front, the standard non-ahc torsion bars will definitely be too stiff, unless you add something really heavy up front, like 600 pounds extra.
For the rear, according to what I've read of others' experience and added to my own, it looks like King springs would be good for you.
Non-ahc rear springs could be viable if you have rear steel bar with swingouts and bike rack etc, in addition to a heavy rack and drawers, i.e. if you go over the rated max rear load.
I have seen that the rear springs (coils) do wear out pretty quickly. After 5 years the capacity is reduced so much that I consider changing them out. This has been the case with both the 80 series and the 100. The fronts can luckily be adjusted to compensate for wear.
I run the strongest OEM ahc rear springs (Brown color dot), and manage to keep pressures within range in normal, daily use. If I load up the car with 5 people and a full boot, the rear pressure will be too high, and I can't get to High without shedding some load.
Thanks for asking. I'm on the road to recovery. I have no idea why I waited so long to get tech stream. It should be mandatory if you have AHC. I discovered the front and rear pressure was extremely low. I cranked the torsion bars way down and go the front within spec. The rear is still extremely low because I need to replace the springs. I'll likely replace the torsion bars as well. My ride has been super stiff (ever since I swapped out the rear springs and torsion bars). I'm excited to get back to normal.
I will say--and I hope this can benefit others because this information was nowhere (that I could find) on this forum or anywhere else--when the torsion bars were torqued and carrying the majority (all?) of the front pressure, it caused the AHC front shocks to rattle/clunk. Neither I nor any mechanic could ever figure out the cause of the noise. It was maddening. As soon as I put pressure back on the AHC and got it into spec, the noise disappeared. So, if anyone has AHC and an unknown metallic rattle/clunk, check your AHC pressure. It's worth noting here, that San Francisco Toyota looked at this three times and never figured it out or even knew to check the AHC pressure.
I'm very grateful for the collective wisdom on this thread. It's a wonderful community.
I will say--and I hope this can benefit others because this information was nowhere (that I could find) on this forum or anywhere else--when the torsion bars were torqued and carrying the majority (all?) of the front pressure, it caused the AHC front shocks to rattle/clunk. Neither I nor any mechanic could ever figure out the cause of the noise. It was maddening. As soon as I put pressure back on the AHC and got it into spec, the noise disappeared. So, if anyone has AHC and an unknown metallic rattle/clunk, check your AHC pressure. It's worth noting here, that San Francisco Toyota looked at this three times and never figured it out or even knew to check the AHC pressure.
I'm very grateful for the collective wisdom on this thread. It's a wonderful community.
Anyone have any thoughts on why my front passenger recently started sagging. I leveled it a few months ago when i did a small 1/2in sensor lift, but the last week noticed my wheel rubbing on the front bumper edge and when i measured my front heights i had almost 0.75" difference. The only thing i can think of is a rock i grazed pretty hard on the trail a few weeks back that gouged up my front passenger rim and blew the back tire out. Nothing is visibly bent or cracked though and the height sensor was fine so i see no relation aside from timing. I also added sliders but that was equal weight to both sides. I do remember having my driver side t-bar cranked to max while my pass side was 1/2 cranked to get the truck level. Still doesn't explain the huge drop in height over such a short period of time. I'm going to re-cross level and then re-level the truck but it just doesn't feel right given it was in spec a few months ago.
Is there any super reliable way to measure ride height and check differences, the "center of hub" is very hard to make precise measurements from especially when the tire and wheel offset from the fender a lot so you can't draw a straight line from the hub, nor can i even tell the center of the hub as i have caps on and the hub is inset way behind the cap.
Also is there any updated AHC brackets, the little "lock tab" on my height adjustment slider broke off and now the only way to tighten and loosen the nut is with an impact and prayer, otherwise the dang thing spins freely. Would really love some kind of stepped bracket with better adjustment!
Is there any super reliable way to measure ride height and check differences, the "center of hub" is very hard to make precise measurements from especially when the tire and wheel offset from the fender a lot so you can't draw a straight line from the hub, nor can i even tell the center of the hub as i have caps on and the hub is inset way behind the cap.
Also is there any updated AHC brackets, the little "lock tab" on my height adjustment slider broke off and now the only way to tighten and loosen the nut is with an impact and prayer, otherwise the dang thing spins freely. Would really love some kind of stepped bracket with better adjustment!
Yep, there's an adjustment/measurement procedure in the FSM but it involves a bit more measuring and math
Hey everyone, new here and did a ton of reading before I wrote this post (thanks for the awesome write-ups). I followed these ABCs and seemingly dialed everything in, but my ride is absurdly bouncy. For context, I recently picked up a 2006 LX470 with 170K miles and noticed that the truck was basically sitting on the bumpstops and the AHC reservoir was basically dry. I have since followed the thread and:
- Flushed and replaced the fluids
- replaced all 4 globes
- replaced the seals on the front shocks (front left seemed to be leaking previously)
- Bled the system again
- Adjusted front and rear heights
- Dialed in pressures using Tech stream (Front 6.9mpa, Rear 6.1mpa, accumulator 10.5)
- Dialed in ride heights (all +/1 0.1 inches)
- Drove around and cycled heights a bunch
- Bled one more time to ensure all air was removed
Hi Jackson
Sounds like a good job on the AHC so far. Missing info on a couple of points:
- What is included in your point "Replaced the seals on the front shocks"?
- Are the actual ride heights also within specs? (not the sensor readings)
- What is the current count of level-marks on the reservoir between Lo and Hi, with heights, weights and sensors within specs?
- Are the damping steps changing during driving, when viewed in TechStream? (Front wheel step, Rear wheel step)
It sounds like the height control works, which means that the actuator valves are not blocked, and I presume that the truck drops to low at that end when you bleed any of the actuators. If the pressures are ok, and the valves are working, there isn't much else than the globes that can be faulty if you have a "pogo ride". There is no magic in the AHC system, quite plain and simple physics actually. You should also be able to bounce the car by hand in each corner, and see a difference in damping if you run a damping steps test. Where did you get new globes from, btw?
Btw 2: Bleeding after changing globes or shocks normally takes a few more rounds than 1 or 2.
Thanks for the reply Uhu!
-I know its an awful image but the seals between the shock and the fluid hose attachment where I saw fluid leaking out
-Physical ride heights are also in spec
-getting about 8-9 graduation change with the new globes on there
-I'm not actually sure about the damping steps because I dont know which parameter that pertains to in TS (Ignore ride heights since this is an older screenshot)
I havent run a damping steps test because it seems like I need a SST tool that I dont currently have. I could be wrong though because its been difficult finding content on the 16 step damping test
The globes I got came from an ebay supplier that had reasonable reviews. However, a couple people have already told me that they're too cheap to be any good...
Link: Front & Rear Suspension Accumulator Kit For Lexus LX470 Land Cruiser J100 99-07 | eBay - https://www.ebay.com/itm/145028690002?mkevt=1&mkcid=1&mkrid=711-53200-19255-0&siteid=0&customid=&campid=5337589904&toolid=10001&mpt=9529726
Finally, I will try bleeding again if it is required. My concern is that I have not seen any difference between the 3 times I have already bled the system. This surprised me because the first round expelled a lot of air while the third time showed only clear fluid. I figured that would have been more noticeable
I took another look at my numbers after dialing them in a few years ago. I got the fronts to 19.75" and rears to 20.5 with AHC and engine "ON". I raised the height control sensors on the front as I started at 19.25" with engine and ahc "OFF". This was done with full tank of gas, no cargo(I have wood drawers & gear that always stay in the vehicle). Pressures were 6.35(average) Front and 6.15(average) Rear, FR Height 0.165 Inch, FL Height= negative -0.433 Inch. This was after driving around a bit and cycling through the different heights. I then loaded the vehicle with fridge, lithium battery(80 lbs), recovery gear, 40 liters of water, tool box etc and retook pressure readings. I primarlly use the vehicle in this loaded manner for camping. Now fully loaded I am showing averages of Front 6.8 and Rear 7.2 with FR Height at 0.039 Inch and FL Height negative -0.339. Gradiations after obtaining 19.75 height and testing unloaded appear to be around 12. I have king coil springs in the rear already. Should I consider a 30mm spacer to bring the rear pressure down a bit or does this seem close enough within the range?
Last edited:
Looking for some help please, I'm attempting a bleed following the instructions at start of this thread and I'm afraid I have screwed something up. 2000 LX, AHC changed height fine before bleed, 5 or 6 graduations. For reference here's the instructions:
Following instructions I put the car in low, syringed out almost 1l nasty dark fluid from tank, refilled with entire 3L can. Went under car, got 250ml+ out of accumulator. Then 400ml+ from driver front. Then 600ml+ from driver rear. Car lowered as expected. Now I have collected 2500ml black fluid. Got up after step 6 and to discovered that the tank is still completely full; the fluid level did not go down AT ALL. I expected the new fluid to be sucked in so I am assuming I have a problem. What should I do? I have not started the car yet (step 7) out of concern it will make things worse. Thanks.
That is expected after step six. Step six lets the weight of the car push all the fluid out of the shocks, only. Step seven is to fill them up again with new, fresh fluid from the reservoir. (Close all doors for pump to work)
Last edited:
IndroCruise
SILVER Star
Press on, @Gartenmeister -- all is good, well done so far. There will be no fluid flow from the AHC Tank until the AHC Pump starts. There is no "suction" involved here. In the static condition with the engine and Active Height Control (AHC) system still OFF, the Levelling Valves in the Control Valve Assembly remain in their 'normally closed' position. AHC Fluid cannot pass from the AHC Tank -- unless there is a leaking Levelling Valve which is possible but unusual.
All that has happened so far in your process is that
- opening the bleed valves near each 'globe' allows a bypass to atmoshere (hopefully into a container!) for AHC Fluid -- this enables flow from the 'globes' and from the 'shock absorbers' [which are mere hydraulc struts, not dampers, in the Active Height Control (AHC) and Toyota Electronically Modulated Suspenion (TEMS) system] -- the flow is due to (1) weight of the vehicle compressing the 'shock absorbers' causing fluid to flow while the vehicle sinks, and (2) nitrogen pressure behind the membrane in the 'globes' causing evacuation of the AHC Fluid in the 'globes,
- opening the bleed valve at the Height Control Accumulator (midway along the LHS chassis rail) allows a bypass to atmosphere for AHC Fluid to flow from this Accumulator -- caused by nitrogen pressure behind the piston in this Accumulator.
HOME | LC100 Factory Service Manual
Comprehensive information on HOME in the manual for the LC100 service manual.
lc100e.github.io
+ New Car Features
+ CHASSIS
+ Suspension
+ Active Height Control Suspension and Skyhook TEMS
This provides a good description with diagrams explaining how the AHC system and TEMS system work, including descriptions and diagrams of the component parts.
Last edited:
Thank you both for the assurances. I completed the bleed procedure without incident. The system is working properly and I gained a couple of graduations but unfortunately the ride has become noticeably harsh (prior to bleed the ride was fair). Certainly not what I was hoping for; guess it is time to look into ordering some new globes.
Thanks again for talking me down.
What pins I have to short in engine bay diagnostic port for clearing AHC codes?
IndroCruise
SILVER Star
