2004 GX470 - Replace AHC without lift?

[AlabamaLX]

I've been thinking about the day when my rear air springs, or any other part of the $$$ AHC System, goes out.

I'm not interested in any lift, so I was thinking of using parts from the 4-Runner V-8, or the FJ Cruiser to convert the GX to a standard suspension set up.

Front Suspension:
1. Remove the factory struts, reuse the coils with new OEM struts from the 4-Runner or FJ Cruiser.

Rear Suspension:
1. Replace rear shocks with OEM shocks from the 4-Runner or FJ Cruiser.
2. Remove the air springs and install the Upper Spring Seats, with built in bump stops, from the 4-Runner of FJ Cruiser.
3. Install a custom made spring perch for the lower spring mount.
4. Install the rear coil springs from the 4-Runner, or FJ Cruiser.

Any thoughts or suggestions?

 

[GXO]

Would work...good plan

 

[dnp]

Just had this very thing happen to my wife's GX late last week. Unless someone can tell me a reason I shouldn't pursue it, I'm considering doing a Strutmasters rear conversion. One of the guys in our club is a mechanic, and he said he's used this system on several brands of cars with excellent results.

http://www.strutmasters.com/category-s/624.htm

Anyone have an opinion before I make this move? It's my wife's car, and a lift isn't in the cards. She has an 80 she wheels, so what I'm looking for is to put the GX back in stock operation and remove the constant airbag unreliability fear from my mind.

Any thoughts????

 

[GXO]

I have no experience with that kit, but I did convert to lifted springs and do not regret it.

 

[dnp]

I have no experience with that kit, but I did convert to lifted springs and do not regret it.

Thanks for the reply. I guess I'm going to try it. If it works, great. If not, I'll send them back.......either way, I'll report what I find.

 

[dnp]

I actually have the StrutMasters kit for the GX470 sitting in my shed.

I didn't like a few things about the kit, so that's why I'm researching doing it with all Toyota OEM Parts.

The kit included; (2) Coil Springs, (2) upper spring retainers, (2) lower spring mounts, and (2) Gabriel shocks

Things I didn't like about the kit;

1. The (2) upper spring retainers and (2) lower spring mounts are basically zinc-plated steel plates with a phenolic donut-type adapter that bolts up in the center of the plates. The phenolic donuts do not fit very snug inside the interior of the spring and have no stop-point to prevent the spring from turning. The lower spring mounts are made to just sit on top of the Air Spring Perch Plate that is welded to the axle and bolt up with one bolt that goes through the centering hole on the factory perch.

2. The system does not have any type of Damper on the upper spring retainer like OEM set ups do. The damper serves as both a cushion and the stop when the spring is fully compressed. These are standard on all OEM set ups and I believe ship with the aftermarket lift kits as well.

I modified the (2) upper spring retainers and changed them to tighter-fitting lower spring mounts, ordered (2) dampers for a 2004 4-Runner V-8, and ordered (2) Bilstein shocks to replace the Gabriels.

I still have all of the components. I can post pics if there's any interest.

Thanks for the detailed description. Yeah, if you can post photos, that would be great. Also, are your concerns that the spring could become detached from its mounting and be "spit out?" It seems like an anchoring tab could be installed to retain the springs in place (in addition to the donuts). That's actually what I had thought about doing. Also, when you say dampers, are you referring to the thin rubber isolators that typically sit between the spring and the spring cups?

On a similar point, are you familiar with the Arnott products? Their "system" is available with 2 rear springs only.

OPINION: This is a really good thread to keep going as, while there are many on the internet that reference the process / parts for lifting a GX, there are virtually no complete threads that tell how to simply convert stock height airbags to stock height springs........This would be a good reference thread for that (especially since it's on IH8MUD, a known enthusiast site!)

 

[GXO]

you can source 4runner springs or even FJ cruiser springs to replace them.

The cups from an FJ Cruiser work well (uppers) and fab up lowers.

Pop in the system and off you go. No idea if the ride height would be impacted, but assume the 4R and FJ would be the same height.

Some pics of my rear during the conversion:

 

[GXO]

You just unplug, unbolt, and remove. Once you pull the relay it won't even know it is gone.

 

[dnp]

1. Yes, keeping the spring in place, without any rotation is my concern.
2. The tab is exactly what I had in mind as well. Dan's photos show it like I want it; with the tab, and welded in place on the factory Air Spring Perch.
3. See item number (8) on the parts list for the damper (AKA Spring Seat) for the 4-Runner.

Thanks for the info.

The other possibility I've been considering is the Arnott setup. Unlike the Strutmasters (and others) setup, this one works by replacing the air bag in the strut with a coil spring. Accordingly, like the front setup, the spring is retained by the strut itself.

Anyone familiar with these folks? https://www.arnottindustries.com/part_LEXUS_Air_Suspension_Parts_yid7_pid141.html

UPDATE: not being comfortable that I've got anyone around here to do "acceptable" fabrication in a timely fashion (my wife's car is sitting, and she's ready to have it back), I ordered the Arnott springs and isolators. Again, because their setup allows for the removal of the airbag itself and its replacement with a coil spring and isolators, this sounded like a reasonable solution to me. For the time being, I will be retaining the factory shocks, but if they prove to be problematic, I will replace those also..........hope this works out to be a suitable solution for a stock-height retrofit. I'll keep y'all informed.

 

[coulter]

I was interested in this same conversion, my question is, this vehicle was also made by Toyota as the Prado in other countries but without the rear air setup. Is there a list of OEM part numbers that could maybe make this car a factory coil conversion?

This is my wife's car, and her first impulse is to just go to the dealers and buy new airbags (the ones we have are leaking) but I'd like to get rid of this system altogether, but only if there's a turnkey solution that has a comfortable factory ride.

My research on the kits available all seem to still require some fabrication work in order to keep the spring in place, I'm just not comfortable doing that work or even knowing where to get done.

Is there a sort of "dummies" package out there that I can just bring to a suspension shop and have my car converted over? I want to keep the factory ride height and smooth riding, I just don't want to deal with these airbags anymore.

 

[coulter]

1. The GX470 has a spring perch welded to the axle just for use with the air spring set up. The Prado has the benefit of being sold either with the air springs, or with coil springs (Don't get me started on how much I wish we could buy the Prado in the US.)

So you can purchase all Toyota OEM parts that will fit, either from the 120 Series 4-Runner V-8, or the FJ Cruiser. All three share the same platform. The spring perch on the axle is not available as a seperate part because it is part of rear axle. Adding the OEM parts from the 4-Runner or the FJ Cruiser with either a custom built spring perch or spring perch adapter is about as close to OEM as you're going to get. Now if you had the rear axle from a coil spring equipped 120 Series Prado laying around you would be 100% OEM.

2. Keep in mind that converting the truck to the coil spring set up, you will sacrifice some of the ride quality VS the Lexus System. The Lexus System gives you the best ride this truck can get, but costs $$$$ when it goes out. I am willing to sacrifice some of the ride quality to the longevity and simplicity of the coil spring set up, some are not.

3. Strutmasters http://www.strutmasters.com/Lexus-GX-470-Air-Suspension-Conversion-Kit-4-p/-gx470-r1-s.htm is the only off the shelf kit I have seen for the GX470 that addresses the fact that there is no coil spring perch on the axle and provides and adapter to convert the air sping perch to accept the coil spring.

4. Do you know anyone who races cars on the weekend? If you do, find out what shop sets up their cars suspension systems. Go by and show them some pics of what you are wanting to do and they can install the parts and weld in the spring perch for you. For a good shop, that's used to modifications for race cars, this would be easy-peezy.

Again, you really need to check and see if the wife is willing to have a firmer ride than the AHC System provides.

Hope this helps.

Really appreciate the information, I had done some research and got a bunch of different answers.

So does the Strutmaster kit have "everything", it's just a matter of installing it? The part that I got confused on was some people were saying you still needed to add an additional adapter on the bottom to keep the coil springs from rotating.
Does the Strutmaster kit include this? Or is this a separate piece?

Regarding the ride quality, would Toyota OEM coils from a 4 runner provide a softer ride? Are there some softer aftermarket shocks like Gabriel or Monroe or OME that would help in the ride department?

I've done suspension work on many cars in the past, but I have zero welding skills so I would have to have a shop do it. I think the "math" that's hard for me to get around is I'm getting pretty close to the cost of just using factory air bags when it's all said and done.

BTW, does anyone have a writeup from something like AllData or a service manual excerpt regarding a simple replace of the factory air bags? Is it an easy job? I'd just like to look at both options, if it's close, I know my wife will insist on the factory ride.

Thanks again

 

[coulter]

1. The GX470 has a spring perch welded to the axle just for use with the air spring set up. The Prado has the benefit of being sold either with the air springs, or with coil springs (Don't get me started on how much I wish we could buy the Prado in the US.)

So you can purchase all Toyota OEM parts that will fit, either from the 120 Series 4-Runner V-8, or the FJ Cruiser. All three share the same platform. The spring perch on the axle is not available as a seperate part because it is part of rear axle. Adding the OEM parts from the 4-Runner or the FJ Cruiser with either a custom built spring perch or spring perch adapter is about as close to OEM as you're going to get. Now if you had the rear axle from a coil spring equipped 120 Series Prado laying around you would be 100% OEM.

2. Keep in mind that converting the truck to the coil spring set up, you will sacrifice some of the ride quality VS the Lexus System. The Lexus System gives you the best ride this truck can get, but costs $$$$ when it goes out. I am willing to sacrifice some of the ride quality to the longevity and simplicity of the coil spring set up, some are not.

3. Strutmasters http://www.strutmasters.com/Lexus-GX-470-Air-Suspension-Conversion-Kit-4-p/-gx470-r1-s.htm is the only off the shelf kit I have seen for the GX470 that addresses the fact that there is no coil spring perch on the axle and provides and adapter to convert the air sping perch to accept the coil spring.

4. Do you know anyone who races cars on the weekend? If you do, find out what shop sets up their cars suspension systems. Go by and show them some pics of what you are wanting to do and they can install the parts and weld in the spring perch for you. For a good shop, that's used to modifications for race cars, this would be easy-peezy.

Again, you really need to check and see if the wife is willing to have a firmer ride than the AHC System provides.

Hope this helps.

Thanks for the help, I appreciate it.

Does the strutmaster kit include the attachment that keeps the springs from rotating, or does that need to be custom made?

Adding up the costs of me buying the kit and having the welding done versus buying the Lexus factory airbags, I know my wife is going to lean towards the original parts and the smooth ride even though I'd be leaning towards a coil conversion.

Not sure yet what I'm going to do, does anyone have an AllData or Lexus service manual excerpt about replacing the factory airbags? I've done basic suspension work in the past.

 

[coulter]

Sorry about the double post, for some reason it took over a day for the response to be posted on the board.

 

[coulter]

coulter,

1. The StrutMasters kit does come with everything you need to install the spring, but it does not have a stop on either the top spring seat adapter or the bottom one. A stop could be added to both plates easily to stop the spring from turning. I personally would not use the upper spring seat adapter they supply with the kit and would opt for the upper spring seat from a 4Runner V-8 120 series. It provides a cushion, and because it's rubber, it also aids in the spring not turning in the mount.

2. The ride quality is unknown. Most of the guys on the forum have the trucks lifted with larger tires, so you're in uncharted territoy. Since the platforms are the same, I am guessing the truck should ride the same as a 4-Runner V-8.

3. I have both the OEM coils from a 4Runner V-8 and the ones from StrutMasters. Not really any difference in height, diameter, etc... Again with no one having done this with either coil spring, ride is unknown.

4. As far as shocks, I prefer the OEM Toyota ones. When I removed the AHC from my 2001 LX470 I originally went with Bilsteins, but found them too firm. I removed them and installed OEM shocks and have been very happy with them.

What year (or part number) V8 toyota 4 runner has shocks that will work with this GX? I'm guessing the same year as my GX? Also, do you have the part numbers for the spring seat?

Also, when you disconnect the factory ride control shocks from the harness, and replace them with conventional ones, does an error message come up on the dash? If so, any way to defeat that?

Sorry for all the questions, it's hard to find much info on these vehicles, they don't have a big following, and most of the people that own them just take them to the dealership to service.

Thanks again

 

[dnp]

I have been looking at what would need to be done to disconnect the AHC electronics on the GX470.

The system uses (2) computers, (1) relay, (1) 50A fuse, and (1) 10A fuse.

The Ride Control Computer (Part Number: 89293-60031) is located under the steering wheel and controls the dampening of the shocks.

The Height Control Computer (Part Number: 89271-60010) is located in the rear of the truck on the driver's side and adjusts the height of the rear air springs.

The relay (Part Number: 90987-02025) is located under the hood in Fuse Panel B.

Both the Air Sus 50A fuse and the Air Sus #2 10A fuse are located in the main fuse panel under the hood.

Some have expressed the desire to remove the rear air springs and install coils, while maintaining the OEM electronic dampening shocks. It's not clear to me if that would work. My guess would be to try and unplug the Height Control Computer while leaving everything else in place and see what you get.

After looking the system over my gut says it an "All or nothing" suspension system like the AHC is on the LX and you can't keep part of the system and ditch the other.

OK, this is general information, and I plan to provide photos and a detailed description shortly, but I wanted to provide some initial findings:

As my earlier post disclosed, my wife's 2003 rear air suspension went out. Still haven't determined if it was the compressor or the bags themselves, but suffice it to say, the rear end sat down.....completely!

Following that occurrence, I set out to determine the best and/or most cost effective way to not lift the truck, but to put it at or as close as possible to the original ride height. Well, it quickly became clear that replacing or refurbishing the factory air system was going to be quite costly. I can't remember the exact figures, but it was going to possibly run into the thousands of dollars to put the rear suspension back into the original configuration. That being determined, I set out to find what I thought would be the best spring / shock setup. To make a long story short, I decided that both the Arnott springs and the Strutmasters kit made the most sense to me. The Arnott setup consists of 2 springs with rubber insulators at the top. No shocks are included, as they retain the use of the factory electronically-controlled shocks (that was appealing to me). The Strutmasters kit contains springs, spring perches, and shocks.

AlabamaLX was above and beyond generous to allow me to try the hybrid Strutmasters kit he configured (the contents are illustrated above) and I also decided to order the Arnott springs. After looking at both, and after looking at how both would mount (and how springs would be retained), I decided to first try the Arnott springs (due mainly to the fact that I wanted see how everything would work with the factory, adjustable shocks.)

A Toyota tech friend of mine installed the springs for me, and I asked him to carefully consider the safety of the springs in place of the air bags. He inspected everything for me, and he said he didn't see any practical way the springs could become dislodged. In fact, he said the bottom perch even has a notch to prevent the spring from rotating.........I'm a big skeptic, so I still want to see / take photos of all of this for myself. That being said, if the top of the spring is retained in a cup and the bottom sits on a perch with a notch, short of one of the shocks coming loose and letting the axle drop down, I'm not sure how the spring could come loose........

The truck sits and rides just as it did pre bag failure. It seems to bottom out a bit when hitting a big bump when the suspension is set on the softer side, but when it had the factory air bags, it used to bottom out ALL the time.....

It seems to ride fine to me know, and my wife agrees. Just knowing there are springs back there, rather than air bags even makes me believe it rides BETTER.........I'll let you know if anything changes, and I may play with the shocks, insulators, etc., but for now, I'm completely satisfied (and parts - shipped - were $294.86)

Photos / more details to come...........

 

[GXO]

Pull the relay and fuse and no issues or errors, did it a long time ago.

 

[dnp]

According to his post, he is still using the OEM Adjustable Shocks, just not the rear air springs. If he pulls the relay and fuses, he will kill both the Suspension Control ECU and the Height Control ECU.

Since he didn't go into detail about much of what was done, I'm guessing he didn't unplug anything AHC related. The system must still be working due to his new coil springs keeping the Height Control System in "Normal" mode, so it doesn't know anything has changed. This would keep the compressor from coming on, warning lights flashing, etc...

I am hoping for more details and pics from the installation to answer some questions.

By the way Dan, your GX build is awesome. Everytime I see it temps me to throw a lift on mine.

Sorry for the lack of details so far. Maybe this weekend I can give more detail and take photos.

BTW, correct on both: no fuses pulled, and I am still using the factory electronically-controlled shocks. No lights flashing, and no compressor running.........so far, so good. (I will say the rear suspension still has the "soft" feel it had when the original air bag suspension was in it. From new, it always seemed to bottom out easier than I thought it should - regardless of the shock settings - and it still does. Hitting an obstacle at a certain speed will cause NO bottoming out in my LX, while the GX did - and still does - bottom out under the same conditions. For that reason, at some point, I may convert to the hydraulic shocks to see if that cures the problem.......the issue is, however, the way it rides is fine with my wife - who drives the car daily - so I may end up leaving well enough alone......

Again, sorry for the lack of reporting so far. Not intentional, just short on time. I hope to rectify that this weekend........

 

[dnp]

Sorry to all for the length of time it's taken me to take photos / respond......life happens.

That being said, I got under the truck last night to inspect how the springs sit in place of the air bags. I took a few photos, but unfortunately, none of them show any more than the following shots.

As I mentioned earlier, I used the Arnott spring kit. It comes with two springs and two insulators only. Factory, electronic shocks are retained. The upper spring is situated in a depression (slight cup) that keeps it from moving out of place, and the lower spring is retained by a raised perch that keeps it from moving out of place. The lower perch is much shorter than the lower perch on my Land Cruiser (last photo), but unless the shock failed to limit droop, it's hard to see how it could become dislocated. Likewise, unless the spring became fully extended somehow, I see no way the top of the spring would work its way out of the cup.

Certainly, additional measures could be taken to secure the spring so it couldn't move at all, but the question is: "is that really necessary?" It seems secure to me. (For what it's worth, my mechanic said they were TOUGH to install, so that make me feel even better that they're going to remain installed.)

From the photos / description, what say y'all?

 

[mracer]

Dnp how is the ride after being able to put a few miles on the Arnott springs? Noticed any sagging when loaded up?

 

[dnp]

Dnp how is the ride after being able to put a few miles on the Arnott springs? Noticed any sagging when loaded up?

To me, the ride is as good or maybe a little better than original. Of course, that's subjective, but I like a little firmer ride than the too-soft-for-me factory air bags. With regard to sagging, I haven't had it loaded, so I can't say for sure; however, due to the perceived spring rate, I'm pretty sure it will begin to sag without a tremendous amount of weight. We never really put any weight in the back, so that wasn't a concern for me. I figured if any of that ever changed, we could always supplement the GX's load-carrying ability with intra-spring air bags.

dnp,

Looks good, glad it worked out.

On your previous post about the rear still feeling like it was "Bottoming out" during a dip in the road, when the rear spring would be at, or near, full compression;

1. My GX does the same with the OEM set up. I was thinking the Upper Spring Seats w/integrated bump stops from a 2004 Toyota 4Runner V-8, part number 48302-35040 would stop this from happening. My LX did the same thing with the AHC system, but after converting over to OEM springs, shocks, and upper spring seats w/integrated bump stops, it doesn't do it anymore. The bump stop should engage the bottom spring perch before the spring reaches full compression giving you a cushion against the "Bottoming out" feeling.

2. I'm not sure how critical the distance between the end of the bump stop and the lower spring perch would be, but it would affect when the bump stops engages the perch. The lower spring perch on the 100 series is around 3/4" tall. I've never measured the one on the 4Runner to compare.

Your assumptions on the upper spring seats seem plausible to me. Since my wife drives the truck 99.9% of the time, I haven't had much seat time in it. She said it rides "fine" now (about as much specificity as I can get out of her on her opinion of the retrofit), so I haven't looked into it much further. I do, however, plan to drive it more in the coming months to see if I can detect any bad characteristics that I believe can be improved. It may well be that the upper spring seats with bump stops will cure the truck's tendency to hit bottom with that solid feel. I will drive it more and report. In the meantime, it's good to know that there are some practical alternatives to having to live with the problematic OEM air bags!