First Bought a UZJ100: 1998 LX470, 198K mi. Failed AHC. Suspension Advice Needed.

[MauiUZJ]

@PADDO Thank you for your informative post. I concur that the 25.5mm Torsion Bars are wholly inadequate in a Non-AHC suspension. As I have learned more about torsion bars, and driven a few more miles with the knowledge gained, I believe I definitely need the 60% or more stiffer front TB's to improve the ride, and I thought it was too stiff at first... But really now I feel the springs allowing rapid movement of the wheel, and the OME shocks with their aggressive valving are trying control the rapid movements of the poorly sprung wheels, and it all is quite jarring to the driver and passenger up front. The front and rear of the vehicle seem to handle bumps quite differently, which is disconcerting. I do not want to take it off road the way it is now, as I think it will stress components in unintended ways, and possibly bend the Torsion adjusting bolts.

Unless you count my 88 Camry LE Alltrac with CDL, this is the first 4wheel drive Toyota I have owned that was not riding on a solid front axle, and three of those had leaf springs. This LX470 rides worse than any of them over rough pavement and potholes at moderate speeds. Wish it were riding at least as good as a Land Cruiser 80 series....

Previous full time or part time 4WD Toyotas I've owned.

85 Pickup, SR5 Long Bed Extra Cab, 22R W. 20R head & Weber 38D, stock height with triple front shocks.
85 4Runner, 3VZE & Auto swap, 5.29 gears, Powertrax No-Slip Rear, 35" SS on 16" deep rims, ~8" lift.
87 FJ60 2F, Stock Height, 4 speed manual, Factory springs
88 Camry Alltrac, 3SFE, 5 speed, and CDL, all stock.
92 FJ80, 3F, Stock Height, 31" BFG's, CDL. (Miss this one the most right now).

@Julian Stead : The PO had a local suspension shop on Maui do what they could for nearly 2k, & none of the parts they removed are still available. I am missing the front & rear AHC shocks, & rear AHC springs that I know of.

Accumulators and pump/reservoir are still in place although it looks like they drained all the AHC hydraulic fluid, and at least the rear accumulators are dead.

Reinstating the AHC would be fine, maybe even preferable for most of this trucks intended uses.
I don't know as I have never ridden in an AHC equipped vehicle. Sounds complicated, but given the FSM and time I am sure i could fix it...


If I found a set of decent take off parts I would consider revamping the AHC, but I have too many projects right now to take that on and I really just need this truck to fill it's intended role ASAP so it can "earn it's keep".

I Posted on a couple of classifieds last night about AHC parts, so we will see what the cost there might be.

The Dealer Quote for getting the AHC working was several thousand more than I paid for the truck.....

Doesn't matter since I would never take it in to them for anything other than the annual safety inspection, free coffee, and to comment on the Gaudy Grill on the new LX570 in the showroom.

I do all my own car repairs and mods, as time and money allow, so I guess I am not your typical Lexus owner.

This coming month I am simply trying to get this truck up to a decent level of functionality, i.e. Riding like a truck is better than feeling like it is on blocks up front.

Later I do plan to off road the LX, or at least load it up and take it on the rough back roads and trails to remote beaches around the back side of the island on family camping adventures....

One fine day...

 

[Dannyboy lx470]

The question as to the adequacy of AHC (25.5mm) torsion bars being left in service after the AHC system has been gutted, instead of replacing them with the correctly rated bars (28.8mm) - or heavier if going aftermarket - often comes up. Here's some fun facts regarding the engineering behind torsion bars. All else being equal if you double the thickness of a torsion bar you increase its rate by 16 times so that extra 3+mm in diameter the conventional torsion bar has over the AHC bar provides significantly more effective torsional force - about 60% more actually. You can go to a site such as swayaway.com and in their Tech Room they have a cool TB rate calculator. Using conventional LC bars at 1.13in v AHC bars at 1.0inch (bar length and lever arm lengths are arbitrary as we're just looking at ratios) you'll see that the thicker bar provides approx. 60% more effective torsional rate at the front wheel. Working on the premise that Toyota's design engineers had big brains, plenty of time and billions of yen I'd like to believe they chose torsion bars appropriately rated for their respective applications. Accordingly anyone who seriously believes they can just reindex underrated AHC bars in a non AHC application and get away with it in the long term will ultimately be disappointed.

Very informative. So the best way is to run a stock OEM bars and get rid of the AHC bars if you decide to put Lc suspension setup in a Lx 470.A standard Oem shocks front and rear and springs a nice setup for normal driving and a nice ride.

 

[hagani]

[q] Hello everyone,

Looks like we have a similar problem and I have posted almost identical thread on clublexus.com but this forum here seems to have a more activity..

So I you let me I just will repost my questions here and one reply from PADDO.

Hello everyone,

just purchased 2000 LX470 with 194k mles and suspension problem. Fluid tank was empty and truck was very low. Indicator on the dashboard was in "L" position with "OFF" light blinking. I drove the truck 120 miles in this condition from the place of purchase to my garage.

Filled tank with oem fluid, pump started to work right away, truck can be raised and lowered with no problem. After filling tank with fluid I discovered that one of the hydraulic hoses (right rear) leaking. Ordered hose from dealer, already received but didn't have a chance to replace it yet. I will do that on the weekend. Also planning to bleed the air from accumulator and all 4 actuators.

Now the main problem I am facing. After filling the tank I took truck for a short test drive. Truck drives like new except for a little bouncy ride on the back (didn't notice the front really but maybe front too). I spent couple of days on this forum and learned a lot about AHC.

My question would be - before I spend $1,200 on 4 new accumulators - what's the chances are height control sensor, bad shock or air in the system could be a reason for bouncy ride??

Also do they (4 accumulators) have to be replaced all at once or I can replace just 2 rear ones for now and later if needed replace two in the front?

Thanks in advance for your input!

Happy Holidays!! [q/]

Message from PADOO:

[q]
Before you spend any money on replacing the damper accumulators or other parts you really need to ensure the system is free of entrained air and your neutral pressures are correct i.e. 6.9 MPa front and 5.6-6.7MPa rear will get you in spec and these pressures can then be further dialed in to optimize your particular damping. High neutral pressures critically affect damping and are undesirable for several reasons. With your pressures in the correct range and the system bled you should then do the L to H graduation test to get a general, collective appreciation of the health of your four damper accumulators - 14 gradations on the reservoir are returned for four new globes and you want to have a minimum of 7 for used globes. At this point Toyota/Lexus recommends they all be replaced. The 16 step test can be used to isolate a failed damper on any particular corner too.If you have normal height and system control and the vehicle hasn't taken on a severe front or rear rise/drop then your 3 height sensors are functional. Go over to ih8mud.com and have a look through the 100 series forums where I've posted many AHC tech threads that cover your current situation. You'll also find my "quick and easy 1 can bleed" method with a search. Its a fast and efficient way to purge old fluid and gases without any wastage or danger of messing up and running out of fluid due to excessive, wasteful bleeding.
Damper accumulators can be changed individually if necessary but it makes far more sense to change the fronts or rears together as the left/right sides are normally hydraulically connected so when one wheel goes into compression or rebound there will be fluid passed to/from the opposite wheel. So if one accumulator is completely blown or severely degraded it will adversely affect its opposite and the overall damping quality. [q/]

And here what I have done:

Thank you Paddo for all the info you've provided. I did follow your advise and bled the system as you suggested in your post at ih8mud.com

Here is what I've got done:

• Replaced the RR pressure hose
• Replaced front and rear stabilizer links
• Bled the system

And results are:

• I have only 4 gradations in the tank going from High to Low and back
• Truck still extremely jumpy and have bouncy ride
• Pressures in neutral: Accumulator - 10.60 / Front Pressure 10.40 / Rear Pressure - 8.90
• Pressure is different every time I go from High to Low and vice versa

Suspension fluid was like coffee with milk - light brownish color

I guess my next step is to replace dumpers..

And I couldn't figure out how to adjust pressure. Can you elaborate on that?

Thank you very much in advance

 

[Julian Stead]

Adjust the torsion bars on the front to lower the pressures to within spec, @PADDO has given full instructions in this post and previous as to what to do. You can buy Citroen spheres that have been adapted to fit, they modify them here in the U.K. But noticed someone on this site managed to get them shipped to the US. Not sure if it is the same supplier I used, but I have them fitted with no issues, I have got my genuine OEM ones recharged and will fit them when I feel the ride deteriorates but I have the Citroen ones fitted for a year now and they still feel great.

 

[Julian Stead]

A fully operating AHC system is a great setup in my opinion, as long as it is setup right it can't be beaten for a unladen truck, so it is worth ironing out any issues you have.

 

[hagani]

Adjust the torsion bars on the front to lower the pressures to within spec, @PADDO has given full instructions in this post and previous as to what to do. You can buy Citroen spheres that have been adapted to fit, they modify them here in the U.K. But noticed someone on this site managed to get them shipped to the US. Not sure if it is the same supplier I used, but I have them fitted with no issues, I have got my genuine OEM ones recharged and will fit them when I feel the ride deteriorates but I have the Citroen ones fitted for a year now and they still feel great.

Just adjusted the torsion bars - 7 complete turns on both

After adjustment pressure still not with the specs:

Accumulator - 10.50
Front - 7.60
Rear - 6.50

Drove it around the block - still the same ride, didn't notice any difference

 

[Julian Stead]

Keep going until you get 6.9, it will go down.

 

[Julian Stead]

Measure your ride height also, did you flush all of the old fluid out?

 

[hagani]

Keep going until you get 6.9, it will go down.

Left side is getting really tight.. Probably can manage another turn or two.. On the right side it going much easier..

 

[Julian Stead]

Mine was the same, is your ride height in spec.

 

[hagani]

Mine was the same, is your ride height in spec.

What exactly do you mean by "ride height in spec"?

I have 34 inches in "N" from the ground to the bottom of the wheel arch

 

[Julian Stead]

Measure from centre wheel to wheel arch, it is metric here, I think mine is 500mm front 520 mm rear. But paddo has it written in his posts, I used his information when I refreshed my AHC. Make sure the height is in spec, then check and correct the pressures.

 

[MauiUZJ]

A fully operating AHC system is a great setup in my opinion, as long as it is setup right it can't be beaten for a unladen truck, so it is worth ironing out any issues you have.

I will have to make it a point to ride in an AHC equipped 100 series...
Thanks for the opinion. I bet your 98 100 rides really nicely after servicing the AHC.

At this point I am looking at going with a Diff Drop, and LC take off TB's to get the front end better sprung, then maybe OEM front shocks after seeing what it feels like. Want to bring the ride up to acceptable while on a budget ASAP. Then go through the rest of the overdue maintenance items before reconsidering the effort needed to recondition the AHC.

Found this thread last night, AHC and a 2.5" Lift....

2-2.5" AHC Lift Using King Coils & Shock Spacers
https://forum.ih8mud.com/threads/2-2-5-ahc-lift-using-king-coils-shock-spacers.945879/

 

[hagani]

Mine was the same, is your ride height in spec.

Measure from centre wheel to wheel arch, it is metric here, I think mine is 500mm front 520 mm rear. But paddo has it written in his posts, I used his information when I refreshed my AHC. Make sure the height is in spec, then check and correct the pressures.

I have had TB adjusted again. So now I have total of 12 complete turns and I hit the end and maxed out on the right side.

After that pressure didn't change much:

Accumulator - 10.70
Front - 7.50
Rear - 7.20

My height from the center of the wheel to the bottom of the wheel arch:

Front - 500mm
Rear - 525mm

 

[Julian Stead]

Is your fluid contaminated, maybe @PADDO can jump in as I am a bit lost to what is could be other than contaminated fluid or your tb are indexed wrong.

 

[hagani]

Is your fluid contaminated, maybe @PADDO can jump in as I am a bit lost to what is could be other than contaminated fluid or your tb are indexed wrong.

Fluid that was coming out of the accumulators while bleeding was beige color, like coffee with milk. I don't know if that indicates contamination or not

 

[Julian Stead]

AHC Fluid color - What is normal/abnormal?

This is a link to a previous thread you might find useful

 

[MauiUZJ]

Looks like this thread is going on to help some Uzj100 owners fix their AHC. Best wishes. If I still had more of the AHC parts I would likely do the same for my wife's vehicle. If we both had UZJ100's & money were no object, I would opt for the SAS in mine. Always have been crazy for solid front axle trucks, common sense be damned...

I wanted to take a moment to thank all those who chimed in earlier and helped me figure out the main issue with my truck...

I am thankful as I now have a path to get this LX into good enough condition where I my wife will drive it.

Currently she does not want to drive it until the new suspension components and front axle are in...

Also thanks for your patience with my lack of knowledge of forum etiquette and the numerous typos in the thread title & throughout my early posts where I was unable to edit or correct them...

Did a bit of reading on the OME parts I have in the truck. Well it looks like I have the 2.5" medium duty OME 860 rear springs, not the 1.5" 865's....

The receipt from the suspension shop clearly stated 1.5" lift, but as stated by the PO they had never worked on an LX or any AHC equipped vehicle before...

No wonder the back looks so high....

In order to balance out the front I will need to bring it up as well.

I Will be ordering the Diff Drop kit, next week after I get paid.

Found OEM T-bars on here for $100, & $100 shipping to Hawaii

Found OME T-bars for $308 with free shipping.

Leaning toward OME TB's and about 1.5-2" lift in front for the extra $108. Then at least the current suspension will be matched better front to rear.

Will see how I like the OME shocks once there are TB's up front with a stiffer spring weight.

Going to work on getting the AHC lights to stop blinking in the the dash... Maybe I'll pull the light bulbs from the AHC indicators, & see if one fits in the failed D position light.

Good luck to all those who still have their AHC parts in their trucks....

 

[labcab]

Looks like this thread is going on to help some Uzj100 owners fix their AHC. Best wishes. If I still had more of the AHC parts I would likely do the same for my wife's vehicle. If we both had UZJ100's & money were no object, I would opt for the SAS in mine. Always have been crazy for solid front axle trucks, common sense be damned...

I wanted to take a moment to thank all those who chimed in earlier and helped me figure out the main issue with my truck...

I am thankful as I now have a path to get this LX into good enough condition where I my wife will drive it.

Currently she does not want to drive it until the new suspension components and front axle are in...

Also thanks for your patience with my lack of knowledge of forum etiquette and the numerous typos in the thread title & throughout my early posts where I was unable to edit or correct them...

Did a bit of reading on the OME parts I have in the truck. Well it looks like I have the 2.5" medium duty OME 860 rear springs, not the 1.5" 865's....

The receipt from the suspension shop clearly stated 1.5" lift, but as stated by the PO they had never worked on an LX or any AHC equipped vehicle before...

No wonder the back looks so high....

In order to balance out the front I will need to bring it up as well.

I Will be ordering the Diff Drop kit, next week after I get paid.

Found OEM T-bars on here for $100, & $100 shipping to Hawaii

Found OME T-bars for $308 with free shipping.

Leaning toward OME TB's and about 1.5-2" lift in front for the extra $108. Then at least the current suspension will be matched better front to rear.

Will see how I like the OME shocks once there are TB's up front with a stiffer spring weight.

Going to work on getting the AHC lights to stop blinking in the the dash... Maybe I'll pull the light bulbs from the AHC indicators, & see if one fits in the failed D position light.

Good luck to all those who still have their AHC parts in their trucks....

Whatever you do...don't replace your "D" light. If you think it's annoying now that it's out, just wait until it works. Then it's really annoying.

 

[MauiUZJ]

Whatever you do...don't replace your "D" light. If you think it's annoying now that it's out, just wait until it works. Then it's really annoying.

OK. Thanks. Good point, I have never had a Toyota new enough that the D bulb actually worked, except the Prius, & it has a backlit digital display, so I have no experience driving at night with D lit.

I'M annoyed at the blinking AHC OFF light right now. The AHC ECU has figured out the front & rear are at different heights since I backed off the TB's a little. Guess it is mad at me for trying to work through this half a** AHC delete and Lift....

Guess this experience further reinforces my tendency to avoid taking my cars to the shops on island. It may take me longer, but If I cannot fix it, then they most likely cannot either, & at least I know what was actually done.

Now to get back to rebuilding that Prius battery....

We only got 10 years and 176k miles of family service out of the first battery in tropical conditions.... Darn...

Bar None, Cheapest DD road car I have ever experienced.

The LX at 10mpg will drop our combined fleet fuel mileage to about 25 if both are driven equally.

Then again, once the LX rides better, The prius will be driven all week, & the LX for family adventures, so we will see how much the fleet fuel consumption really is then...