LX470 AHC Stiff Ride Correction

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wkbogie

wkbogie

Joined
May 16, 2016
Threads
8
Messages
41
Location
Raleigh, NC
Hey Guys,
I bought a 1999 LX470 with 165k on the clock. It rides extremely rough on expansion joints but handle speed bumps like velvet. It is all stock and I plan to keep it that way except for some 256/75/16BFG's and roof rack.

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After spending countless hours on here I decided to buy techstream for $35 on Amazon and give it a try. It didn't work on my windows 7 but did work on XP. Just needed to go into the program and turn a "0" to a "1". Also turned off the steering wheel autoway mode, since it squeaks like crazy.

When connecting, it defaulted to a 1998 LC, so I had to change that in order to get it to see all the parameters.
20160729_151843.jpg

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Then I ran a suspension check. After that I clicked the "data list" button to see the pressures.

AHC Pressure from the FSM-
Spec calls for
Front 6.9+/-0.5 MPa
Rear 5.6-6.7 MPa

Before:
Front 8.1mpa-g
Rear 6.8mpa-g
Accumulator 10.2mpa-g
20160729_152610.jpg


So, I jacked up the truck and turned the TB bolts 6 complete turns each. Then i drove around the block.
After:
Front 6.7 mpa-g (pressure lowered 1.4) = 0.23mpa-g/1 full turn of TB bolt
rear 7.1 mpa-g (pressure raised 0.3)
Accumulator 10.2 mpa-g
20160729_161756.jpg

After driving it for a day or two, I would say the ride is about 50% better. I know this is hard to quantify, but it is def better. I can still feel every crack in the road, but it doesn't quite feel like I am going to shake all the bolts loose in the truck.

So, my next step is to add some 30mm coils from an Australian company I just ordered on ebay. I am hoping it will lower the rear pressure about 1.0mpa. If it does not get me below or close to 6.0mpa, I will then order and install new springs with some spacers.
2 Rear Coil Spring Spacers 30mm Toyota Lexus LX470 V8 Polyurethane 4x4 New Pair

You guys have alot more expierience than I, so feel free to sprinkle some knowledge if I am off base here.

Thanks,
Bogie

EDIT: I did flush the AHC fluid with fresh Toyota fluid, that did help a bit. Also I have 10 graduation in my AHC fluid tank when going from low to high and back.
 
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Does changing the suspension setting from Comfort to Sport II stiffen the ride or does it feel the same? AHC fluid flush is very easy and made a small but noticeable difference in ride quality for my '01.

Looks like you're off to a good start. Took me about a week to get TechStream to talk to a WinBook running Windows 8.
 
It wouldn't hurt to check to the condition of your AHC fluid (and the level).

Mine had gotten low at some point and I had either air or nitrogen (from the globes) in the system. Once I flushed/bled the system it got a LOT better.

I am going to drive it for a week or so and then do it all again, so I can get a better infusion of 'new' fluid. The fluid I took out of it was sort of amber colored. During my flush/bleed I did not get any of the new 'pink' fluid to come out, so I am going to do it again in the near future. Even so, the ride (at present) is much better.
 
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With a '99 you've got to expect the 4x damper accumulators (aka spheres, globes, gas springs) to be nearing the end of their effective life if they're originals, but you can still optimize what you've got without any big outlay in $.
Fresh fluid with its associated bleed is a great start, particularly if you don't know when it was last changed. Search for my "1 can easy bleed procedure". Quick, easy, can't screw up and doesn't waste new fluid. If the fluid is really old and contaminated you can do a follow up bleed in a week or three.
Start with basics like tire pressures, inspect your shock actuator bushings and cushions etc. New front/rear sway bar link ends with their cushions returned a huge improvement for me, helps to stop telegraphing road noise chatter into the body as well as improves steering feel etc.
Ensure your FR and FL are even in heights, i.e. front is level. If one side has sagged (usually the DS) then the damping response balance between torsion bar spring and gas spring isn't optimum. The gas spring side of the damping has a faster, more sensitive response than the torsion bar mechanical spring and if the balance between these two factors is off then you get poor and uneven damping, harshness etc.
You'll be lucky to get 1MPa drop in rear pressure with just spacers, expect closer to 0.5MPa, but it's all good and going in the right direction.
Do the L to H graduation count test to gauge the general state of health for your globe accumulators. If you get 9 or 10 grads then your damping should be fine - 14 is new, 7 Toyota says to replace. If interested you can put the system in test mode and manually step through the damping from softest to hardest. This is good if you suspect one corners damping is worse than the others as you can walk around and check the compression/rebound effort at each corner in your driveway. You can also lock damping in the softest setting and go for a drive. This is actually helpful if you want to determine if a damping issue is predominantly a mechanical/hydraulic or a damping control issue.
Probably enough to chew on for the time being;)
 
Forgot to tell you guys, I did flush the AHC fluid with Toyota fluid and I have 10 graduations in the res when going from high to low or vice versa.
 
You guys rock!

Kinger- Yeah, I am not sure I can really tell much difference with the AVS. Techstream shows the various combonations of the 2 "ON/Off"'s working when I select different settings. is that what you mean?

Flint- Haha! Oh yeah, my fluid was black as tar. I could tell a little difference after the flush.

Praddo- Wow, now that is a knowledge downpour! Thanks! I think I need to add some tests to my todo list.
I used your post for the fluid bleed, super quick and much easier than brakes!
PADDO said:
Start with basics like tire pressures, inspect your shock actuator bushings and cushions etc. New front/rear sway bar link ends with their cushions returned a huge improvement for me, helps to stop telegraphing road noise chatter into the body as well as improves steering feel etc.
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Alright, I know what the sway bar links are but do you have a pic of the shock actuator bushings/ cushions? Is that just the rubber piece in the shock eyelets?

PADDO said:
Ensure your FR and FL are even in heights, i.e. front is level.
Click to expand...
Good point. I will get on this also.

PADDO said:
If interested you can put the system in test mode and manually step through the damping from softest to hardest. This is good if you suspect one corners damping is worse than the others as you can walk around and check the compression/rebound effort at each corner in your driveway. You can also lock damping in the softest setting and go for a drive. This is actually helpful if you want to determine if a damping issue is predominantly a mechanical/hydraulic or a damping control issue.
Probably enough to chew on for the time being
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Not sure how to do this one. I will look around on here when I get some time and find a procedure.
 
PADDO said:
Don't be afraid to experiment with your pressures either. "In spec" and optimized aren't the same.
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Yeah, i think I would like it softer than firmer, so maybe I should get that pressure lower and then adjust accordingly.
 
PADDO,

I followed your quick (and easy) 1 can method to flush the fluid and it was 'spot on'. When I finished I had just a tad over 'max' fluid level in the reservoir and the ride quality had already been improved. My initial globe test (graduations between high and low positions) gave me a paltry 7 grads, so no doubt my globes have seen better days. I have a second can of fluid and will likely re-flush the system in a week or so. I want to get as much of the old fluid out as possible and any remaining air/gas.


But for now....I plan to get techstream, balance everything the best I can and then look at doing coils in the rear and replacing the globes a bit later, then do a 'proper' balance.

Thank you so much for all your hard work and sharing your knowledge here.

Flint.
 
After doing a front and rear sway bar refurb, my soft is super soft. The rest of my AHC is all in spec and well maintained. I vary the comfort setting a lot when driving, I change it depending on road type. Roads can be tight and twisty in the uk and the soft can get too wallowy.
 
@wkbogie Lowering pressure = more spring force which may make your ride more sensitive to road noise as the steel springs have a different response and natural frequency to the gas/hydraulics. If you're at 6.7 try going down a little; try going up to 7.1 or so. You'll find a sweet spot for your system.
Edit: you can adjust your TBs on the ground, no need to lift the front end. FSM actually says to do it on flat level ground, at most I get 60-70ftlbs when adjusting.
 
So what all is involved with the sway bar refurb/ actuator bushings?

Sweet! I will def try the TB turns on the ground so I can play with the pressures. I am following what you are saying about metal frequencies, good point.

Ran out and measured my height. They are all pretty close to each other.
From the top of the wheel arch to the center of the hub:
DF 19.5" PF 19.75"
DR 20.5" PR 20.75"
 
Having used Super Pro and Energy Suspension link end cushions I prefer plain old OEM Toyota rubber to be honest. I'm sure those MOOG and Rocas would be fine too though and get the job done.
For the shock actuator bushings make sure you either purchase LX specific, or if buying from a Toyota supplier make sure you get "with AHC" parts from 2006/2007 LC.
Try these numbers: Bushing, shock, front absorber 9090389016; cushion front shock No.1 9094801075 and cushion No.2 9094801076 ( I seem to have an old number 9054017007 in my notes).

I'd knock the easy stuff out first and leave the shock actuator bushings and cushions to absolute last if you're still not happy with the ride, unless one or more are obviously blown out. Replacing the cushions involves disconnecting the shocks hydraulic line, re bleeding etc. To do the bottom bushing ideally the actuator should be removed and it done on bench with a press or vice/chisel to avoid potentially inducing a leak in the shaft seals. Bushings can be done in situ, but less risk and ultimately easier to do it on a bench, particularly if you're replacing the cushions imo.
 
I'm going through the same thing with the same year truck and similar mileage (160k)I think you described the ride perfectly. On the highway it's a pillow and I find it hard to keep my eyes open its so quiet and smooth but on backroads I do feel all the little cracks. Id compare it to a truck running bilstiens where they want you to feel everything for performance reasons. I have almost identical pressures as you. I have a brand new set of AHC rear springs in the garage, just waiting on my 30mm spacers to come in from Slee (which by the way the price for 30mm spacers has doubled to 80$ for a pair). When I get all this in I'll chime in on the pressure adjustment and the ride quality so you can get feedback on how much a difference this will make. I don't pull much (just a set of two seater Jetskis) but I do camp and drive on some tricky beaches every now and then.
I've driven a non AHC landcruiser before at the beach and the ride that you we have now from a aging AHC system that is stiffening is pretty close to a stock cruiser. (Enough to not justify a conversion unless I wanted lift.) The body roll and turning felt "different" but not out of control/sort, just valved differently.

I'm going to get it as good as I can get it and just maintain it and run it. I'm curious to see how you make out since we are running similar rigs.
 
Is it an easy job to change the springs?
 
99RichieLx470 said:
I'm going through the same thing with the same year truck and similar mileage (160k)I think you described the ride perfectly. On the highway it's a pillow and I find it hard to keep my eyes open its so quiet and smooth but on backroads I do feel all the little cracks. Id compare it to a truck running bilstiens where they want you to feel everything for performance reasons. I have almost identical pressures as you. I have a brand new set of AHC rear springs in the garage, just waiting on my 30mm spacers to come in from Slee (which by the way the price for 30mm spacers has doubled to 80$ for a pair). When I get all this in I'll chime in on the pressure adjustment and the ride quality so you can get feedback on how much a difference this will make. I don't pull much (just a set of two seater Jetskis) but I do camp and drive on some tricky beaches every now and then.
I've driven a non AHC landcruiser before at the beach and the ride that you we have now from a aging AHC system that is stiffening is pretty close to a stock cruiser. (Enough to not justify a conversion unless I wanted lift.) The body roll and turning felt "different" but not out of control/sort, just valved differently.

I'm going to get it as good as I can get it and just maintain it and run it. I'm curious to see how you make out since we are running similar rigs.
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Nice. We can figure this out together. The TB twist did help a bunch, just not where I think it should be for a Lexus. I am glad mine is not just due to someone beating on it too hard. I bought it from a family at the coast that towed a small boat every now and then, but nothing crazy or over long distances.

Thanks for the info on a non-AHC. I have toyed with the idea of a strutmaster conversion. This ride is down right embarrassing with others in the car. It is nice to know Lexus does ride better(when it works of course).

So you are going to jump to new AHC coils and 30mm spacers? Please let me know how you install goes, my spacers are otw from Australia and should be here this week. I think mine were $60? on ebay. I may try the sway bar bushings and links as well after the spacers. Mine look alright, but they are 17 years old. have you done any of those?
I can't wait to get this thing riding smooth, my wifes RX with 155k rides better than this.
 
I'm still waiting to find someone else that installed new OEM springs and 30mm spacers in rear and pressures didn't come down to spec, though thinking it may be aging accumulators. ;-)

BTW, we need to figure out how to due a full core dump of PADDO's knowledge....priceless stuff over all the AHC threads. Now if he'd just buy a 200, so if they ever start to fail, he'll be ready for us.
 
wkbogie said:
Nice. We can figure this out together. The TB twist did help a bunch, just not where I think it should be for a Lexus. I am glad mine is not just due to someone beating on it too hard. I bought it from a family at the coast that towed a small boat every now and then, but nothing crazy or over long distances.

Thanks for the info on a non-AHC. I have toyed with the idea of a strutmaster conversion. This ride is down right embarrassing with others in the car. It is nice to know Lexus does ride better(when it works of course).

So you are going to jump to new AHC coils and 30mm spacers? Please let me know how you install goes, my spacers are otw from Australia and should be here this week. I think mine were $60? on ebay. I may try the sway bar bushings and links as well after the spacers. Mine look alright, but they are 17 years old. have you done any of those?
I can't wait to get this thing riding smooth, my wifes RX with 155k rides better than this.
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Its actually three of doing this. I have the same year model LX470 as you. I am just getting started looking at the AHC. I've been trying to educate myself before diving into it. So far....just flushing the fluid (mine had LOTS of air/nitrogen in it) has made a big difference.

But new rear springs and spacers will be in order for mine (maybe King Springs). A second flushing soon to be done. Next, a techstream program to see where I am with front to rear balance, then more than likely new globes (for mine). Then put everything in order. I really like the suspension and would be happy with a properly operating system. If the pump fails or something else 'pushes it over the edge' cost wise, then I would consider a conventional suspension.

So far....the system has not been hard to work on....and certain members here have already pioneered the hard stuff and shared their knowledge with us (Thank You).
 
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