LX470 AHC Stiff Ride Correction (1 Viewer)

[flintknapper]

I noticed that the front and rear 'globes' have different part numbers, so apparently there is a difference (if only internal) between the two. Does anyone know if the rear globes will physically fit in the front....and IF so, what the result would be? (I.E. better carrying capacity, longer life, none of the above)?

Wondering if 4 rear globes could be used instead of the stock set up?

 

[ihadmail]

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.

My new springs along with Slee 30mm spacers did not lower my pressure back to within the stock range. I'm lifted 2" over stock though so that's expected. The new springs and spacers did lower my pressure enough that I can still go into high when loaded down for a week long trip.

I noticed that the front and rear 'globes' have different part numbers, so apparently there is a difference (if only internal) between the two. Does anyone know if the rear globes will physically fit in the front....and IF so, what the result would be? (I.E. better carrying capacity, longer life, none of the above)?

Wondering if 4 rear globes could be used instead of the stock set up?

The rear globes are physically taller and are filled with a higher nitrogen pressure. They will fit in the front location. Results of putting them on the front are a slightly stiffer ride and higher damping rate. Similar to switching to billstein 5100s vs stock struts on a Tacoma or 4Runner.

Also by placing rear accumulators (globes) on the front you're venturing into slightly uncharted territory and will have to play around to find the new sweet spot for neutral pressures.

 

[99RichieLx470]

My spacers are coming today. Unfortunately I won't be able to install my stuff this week, I'm going camping for a week and leaving today. I really wanted to get these in Before I leave but I digress.

As far as what spring to select, I think you can make anything work with some tinkering.
Yes non AHC springs will be stiffer but you can always release the torsion bars, change the shock dampening inside and adjust tire pressure to get what you need.

I was gonna go with a non AHC cruiser spring
or something equivalent but I have to keep the ride "wife approved" as this is our biggest vehicle and she uses it quite a bit. I hope I don't get burned. New AHC springs were 120$ a piece and spacers were 80$. That's a deposit towards a conversion to something else. I don't mind spending money but I don't like spending it twice.

With a 2" lift over stock, ihadmails truck is not truly a comparable model. Being lifted will mess with the pressures, none the less his feedback is valuable. Being able to ride in H loaded says that the spacers and preload are making a difference.


I'm a realist I don't think I'll get the ride it had in 1999, but I think I can get 80% of the ride, 100% functionality and a 10-15 % increase in load capacity carry while retaining the AHC. I'd be very happy with that on a almost 20 year old rig.

 

[DirtDawg]

My new springs along with Slee 30mm spacers did not lower my pressure back to within the stock range. I'm lifted 2" over stock though so that's expected. The new springs and spacers did lower my pressure enough that I can still go into high when loaded down for a week long trip.

You might want to give the King springs a try. I've got a pair on the way and @Ramathorn15 is running them right now with what sounds like no complaints.

 

[KINGER]

Sounds like there are a bunch of us who have adjusted everything to within spec with TechStream, the ride is satisfactory but needs improvement and the next thing is probably replace globes at approx. $1600 for parts.

I've headed off some big ticket items (twice repaired DS height sensor) but I think that as soon as something big goes and I can't fix it the AHC system is getting pulled. It's a nice convenience feature for parking garages, etc. and I'm sure the ride with new globes is great. But, an OME 2.5 Medium lift would be about the same cost and cheaper in the long run. Anyone else thinking like this?

I second the call for an aggregation of PADDO's AHC knowledge (and 200-series purchase). If not for PADDO's posts I'd have brought it to a dealer to have them piddle around and possibly not fix it for $$$. Thanks PADDO!

 

[PADDO]

I noticed that the front and rear 'globes' have different part numbers, so apparently there is a difference (if only internal) between the two. Does anyone know if the rear globes will physically fit in the front....and IF so, what the result would be? (I.E. better carrying capacity, longer life, none of the above)?

Wondering if 4 rear globes could be used instead of the stock set up?

I've been running rear globes in the front for a while with no issues whatsoever. Posted something about it previously. The differences between the two are the rears are 500cc and charged to 2.65MPa new, fronts 400cc and charged at 2.25MPa, identical fittings. I have something like 20 grads on the tank going from L to H fwiw. As new rears globes have a slightly higher pressure you can have a slightly higher neutral pressure for the same damping response if nothing else is changed. Practically, the +0.4MPa charge for a new in box rear globe fitted to the front means you just need to compensate less with the torsion bar adjustments if you change front weight, height or the TBs have set. Its all about finding and maintaining the ratios of the working hydraulic pressures v the gas spring pressures at their interface in the damper assembly orifices and their variable metering valve. It all falls within a crank or three on the TBs and experimenting with front/rear pressures that work for your ride heights and weight distributions.

 

[PADDO]

Sounds like there are a bunch of us who have adjusted everything to within spec with TechStream, the ride is satisfactory but needs improvement and the next thing is probably replace globes at approx. $1600 for parts.

I've headed off some big ticket items (twice repaired DS height sensor) but I think that as soon as something big goes and I can't fix it the AHC system is getting pulled. It's a nice convenience feature for parking garages, etc. and I'm sure the ride with new globes is great. But, an OME 2.5 Medium lift would be about the same cost and cheaper in the long run. Anyone else thinking like this?

I second the call for an aggregation of PADDO's AHC knowledge (and 200-series purchase). If not for PADDO's posts I'd have brought it to a dealer to have them piddle around and possibly not fix it for $$$. Thanks PADDO!

You are welcome. I hate to see good systems screwed up by technicians who are flying blind and haven't bothered to fully learn their craft. I'm a retired Military Technician and Engineer and making $hit up on the go for critical systems wasn't an option. I was also in a position to be walked and talked through the AHC/AVS systems and their diagnostics on purchasing a new LX when the brand was introduced to challenge RR in Aus. Lexus Aus ran a "geek squad come Genius Bar thing" to blow the Range Rover/Land Rover Experience thing away which was great if you're into servo and control systems engineering. Most people were interested in the wicker hamper, Pavrotti CDs and nice bottles of wine that came with the purchase. I was more interested in this "hand held SST tester thing" ....and the wine.
Those height sensor assemblies are expensive, if there is a next time and all you need is the actual sensor potentiometer then grab a Dorman 924-755 height leveling sensor for $55. Work great.
I'll take a 200 but I'm actually looking around for a GX project.

 

[whitenoise]

From the OP's description of the issue, and based on the AHC work he has already completed, I would say that the AHC system has less to do with the problem than control arm bushings. Most of the isolation from expansion joints and such "impacts" is due to the bushings in the front lower control arms, especially the aft bushings on them. If the steering wheel also feels buzzy over impacts then the steering rack mounts also need to be looked at. I would not use anything but stock OEM or OEM replacement natural rubber bushings in those locations. They are good enough to last at least 75-100k miles and the aftermarket polyurethane stuff, while durable, simply cannot match the level of isolation offered by the stock parts.

 

[99RichieLx470]

I noticed rock auto offers an aisin brand hieght control sensors and assemblies for front and rear for 150$ each.
Wondering if anyone has run these ?
looks Like a good compromise between the two parts. After reading Paddos response my natural thoughts would be a used rear globe would be a suitable replacement to an oem new front one.

 

[PADDO]

With a 2" lift over stock, ihadmails truck is not truly a comparable model. Being lifted will mess with the pressures, none the less his feedback is valuable. Being able to ride in H loaded says that the spacers and preload are making a difference.
I'm a realist I don't think I'll get the ride it had in 1999, but I think I can get 80% of the ride, 100% functionality and a 10-15 % increase in load capacity carry while retaining the AHC. I'd be very happy with that on a almost 20 year old rig.

Lifting raises pressures, adding weights raises pressures but these consequences can be compensated, for the most part, if you understand and work with the interactions between the variables. Torsion bars can be adjusted, we can mix accumulator globes, add spacers and uprated coils from the AHC OE 90lb/in to Kings at 130 lbs/in or some combination of an 80 series coil up to OE LC coils at 170 lbs/in. We know how a normally functioning system responds to height (i.e. at stock weight a 1 inch front sensor lift ~ + 0.6 MPa {edit: that's rear pressure, front actually goes up 2.2MPa per inch} pressure) or weight (210 lbs over the rear axle ~ +1 MPa) so you can go a long way towards counteracting the delta from OE design.

 

[KINGER]

A question about AHC pressures: "within spec" vs. comfortable.

After cranking the tbars to get AHC front neutral pressures within spec I noticed the ride in the front became rougher. I assume this is because more weight is being carried by the torsion bars to relieve the load carried by AHC (and possibly extend the life of the globes). I'm considering backing off on the tbars to get a more compliant ride, even at the expense of increased neutral pressures. Smart? Stupid?

 

[DirtDawg]

I do want to point out that a recent solution to a case of "feel every crack in the road" was to replace the actuators. He had spent time and money replacing virtually every component on the system except for the actuators and those ended up being the issue. Not saying it's your issue, but really try to isolate the worn/malfunctioning part before you go throwing money at your rig.

 

[PADDO]

I noticed rock auto offers an aisin brand hieght control sensors and assemblies for front and rear for 150$ each.
Wondering if anyone has run these ?
looks Like a good compromise between the two parts. After reading Paddos response my natural thoughts would be a used rear globe would be a suitable replacement to an oem new front one.

The unknown is what is the residual charge in the used rear globe? You can't assume any sort of linearity between how the fronts and rears loose their charge over time and a pre loved front globe at, say, 2.1MPa (or new at 2.25) is preferable to an old rear at 2.0MPa. The additional volume a rear offers, over a front, probably doesn't add much to the equation all up because the design volume of the front is a function of the shock actuators displacements when stroked. So having a rear fitted to the front isnt going to give you more travel or anything like that. But that said, I like my rear globes on the front: maybe it's because they had more charge than the globes they replaced (I had 12 grads L to H) and maybe I've found a better balance between spring lift v gas charge and the puny 1" sensor lift I have today.

 

[PADDO]

A question about AHC pressures: "within spec" vs. comfortable.

After cranking the tbars to get AHC front neutral pressures within spec I noticed the ride in the front became rougher. I assume this is because more weight is being carried by the torsion bars to relieve the load carried by AHC (and possibly extend the life of the globes). I'm considering backing off on the tbars to get a more compliant ride, even at the expense of increased neutral pressures. Smart? Stupid?

Smart to adjust for optimum. It's easy to screw the TBs down for a pressure of 6.5 "in spec" then back off to 7.4, still "in spec" but vastly different damping experience. Please remember that "spec" is for P rated tires at 29/32 psi, new globes, new bushings, cushions, factory weight........

 

[PADDO]

I do want to point out that a recent solution to a case of "feel every crack in the road" was to replace the actuators. He had spent time and money replacing virtually every component on the system except for the actuators and those ended up being the issue. Not saying it's your issue, but really try to isolate the worn/malfunctioning part before you go throwing money at your rig.

Who Dat? and was it new actuators or the new fluid and bleeding or the new bushings and cushions? I've got pages and pages of pm on this topic and I can't recall a definitive case where fitting just new shock actuators was the single definitive fix. Not saying that a blown, severely leaking actuator shouldn't be changed (and fitting "new shocks" is the go to solution for those technicians not AHC savvy) but it's hard to not consider the positives of fresh fluid, bleeding and new bushings too.

 

[DirtDawg]

Who Dat? and was it new actuators or the new fluid and bleeding or the new bushings and cushions? I've got pages and pages of pm on this topic and I can't recall a definitive case where fitting just new shock actuators was the single definitive fix. Not saying that a blown, severely leaking actuator shouldn't be changed (and fitting "new shocks" is the go to solution for those technicians not AHC savvy) but it's hard to not consider the positives of fresh fluid, bleeding and new bushings too.

Well I retract my statement... Just scanned through every AHC thread and can't find what I was looking for. I swear I went through a thread where some guy was complaining of feeling every bump in the road, he replaced globes, shocks, and I thought I read the actuators (correct term? The thing the globes screw into), solved his issues. But maybe my month break from the forum just made me a little fuzzy in the head.

 

[PADDO]

There's a guy who replaced 3 of his four damper assemblies (the rail mounted gadgets that the globes screw into) and that fixed his problem. His stepper motors had stopped responding, cooked he felt. I've got a ton of pm with him. Maybe that's who you're thinking off? If the stepper motors are suspect you can do a resistance check and put the system in test to see/feel if they are being switched from soft to hard. Driving while monitoring Techstream is valuable and locking the system in soft or medium or whatever and driving to try and isolate mech/hyd issues from control issues is good too.
What's I guy gotta do to get a month off the forum?

 

[DirtDawg]

There's a guy who replaced 3 of his four damper assemblies (the rail mounted gadgets that the globes screw into) and that fixed his problem. His stepper motors had stopped responding, cooked he felt. I've got a ton of pm with him. Maybe that's who you're thinking off? If the stepper motors are suspect you can do a resistance check and put the system in test to see/feel if they are being switched from soft to hard. Driving while monitoring Techstream is valuable and locking the system in soft or medium or whatever and driving to try and isolate mech/hyd issues from control issues is good too.
What's I guy gotta do to get a month off the forum?

That's who I'm thinking of. Glad to know I'm not going completely insane. Working on a job site in BFE with no internet besides at the office trailer means very little forum time.

 

[lethal1]

What I wouldn't give to have some of this expertise closer to me in Birmingham AL. I am wanting a 1" sensor lift and to put 33s on my LX and to be done with it. I can't find a single shop or mechanic willing or able to do it. I'd do it myself but my current living arrangement won't allow me to do it myself

My AHC functions perfectly so my next move is the bushings and end links and then hopefully I can find a mechanic to do the lift and mount the 33s.

 

[wkbogie]

I was gonna go with a non AHC cruiser spring
or something equivalent but I have to keep the ride "wife approved" as this is our biggest vehicle and she uses it quite a bit. I hope I don't get burned. New AHC springs were 120$ a piece and spacers were 80$. That's a deposit towards a conversion to something else. I don't mind spending money but I don't like spending it twice.

I am in the same boat. My wife loves the LX but not the ride. We are expecting our first child in a couple months and this thing NEEDS a softer ride by then. Or else...

I'm a realist I don't think I'll get the ride it had in 1999, but I think I can get 80% of the ride, 100% functionality and a 10-15 % increase in load capacity carry while retaining the AHC. I'd be very happy with that on a almost 20 year old rig.

Agree 100%

Praddo- 1st off, thanks for your service to our country.
2nd, Looks like you are pretty close to me. I am in Raleigh. Maybe one day I can buy you a few beers and talk cars. I am pretty sure I could sponge up some knowledge!