Replacing springs with AHC

[Brett19648]

Hey wondering if anyone has information and part numbers handy on OEM replacement spring options.

My AHC is operational but I’m only getting 5 bars on the reservoir going from L to H. I have the globes and a few cans of AHC fluid ready for the swap.

I was thinking while I’m at it I may swap in new springs. I assume my original ones from 2006 are sagging. Are there any other OEM spring options that were offered for vehicle configurations in other markets? Or is there perhaps a spring spacer that would match the shock spacer distance?

I’m considering doing the 30mm shock spacers and would like to add a similar height for the springs. i figured doing a similar spacer for both would keep the AHC fluid pressures in the proper range. Not going to be adding a ton of weight so don’t need heavy duty/firmer springs. If I could net 1-1.5” in lift and not mess with AHC function that would be great. I would then also be doing the AHC sensor lift.

I figured it’d be a good time to order some OEM parts with the 25% off Toyota sale going on.

 

[2001LC]

First counting graduation. Without AHC flush and adjust (AHC F&A) first. Has minimal diagnostic value.

We need pressure readings, after AHC F&A. To make call on springs. That said, I do find AHC coils (springs) in AHC system weaken with age. We do, get a benefit, in reducing pressure at stock sensor hieght. With stock coils and or 30 mm coil spacers (donuts).

If going to do any work on AHC, You must be able to, read pressure.

If doing a sensor lift, We then need aftermarket coils. King AHC coils with spacer (poly donuts) on top coils. 10mm, 20mm. Even 30mm coil spacers, if lots of extra weight & height, may be justified. Pressure reads is key, and make the call.

I use www.partsouq.com for parts number with my VIN.

I usually use Land Cruiser AHC coils (option in 06-07 only) in LX. The LX coils are a bit softer for ride comfort, LC a bit stiffer. Most can't notice differance.

Hers 07LC link for you:

https://partsouq.com/en/catalog/genuine/vehicle?c=Toyota&ssd=%24%2AKwGCtqeS48eD9PuJgvC4jNrO7un3homEhZeRktTxzZXZxZSOy7Gy_pOaldnClI7Lra_1-eKHhfuOg9vWy4SAhYeSnZTXisXBkoaPhoSEhpbFxZbTk4yV5ev8hdnXt532-Pb1-veWxcWd2dWUjYLMAAAAAHilWGM%24&vid=0&q=JTEHT05J872104130

 

[Brett19648]

First counting graduation. Without AHC flush and adjust (AHC F&A) first. Has minimal diagnostic value.

We need pressure readings, after AHC F&A. To make call on springs. That said, I do find AHC coils (springs) in AHC system weaken with age. We do, get a benefit, in reducing pressure at stock sensor hieght. With stock coils and or 30 mm coil spacers (donuts).

If going to do any work on AHC, You must be able to, read pressure.

If doing a sensor lift, We then need aftermarket coils. King AHC coils with spacer (poly donuts) on top coils. 10mm, 20mm. Even 30mm coil spacers, if lots of extra weight & height, may be justified. Pressure reads is key, and make the call.

I use www.partsouq.com for parts number with my VIN.

I usually use Land Cruiser AHC coils (option in 06-07 only) in LX. The LX coils are a bit softer for ride comfort, LC a bit stiffer. Most can't notice differance.

Hers 07LC link for you:

https://partsouq.com/en/catalog/genuine/vehicle?c=Toyota&ssd=%24%2AKwGCtqeS48eD9PuJgvC4jNrO7un3homEhZeRktTxzZXZxZSOy7Gy_pOaldnClI7Lra_1-eKHhfuOg9vWy4SAhYeSnZTXisXBkoaPhoSEhpbFxZbTk4yV5ev8hdnXt532-Pb1-veWxcWd2dWUjYLMAAAAAHilWGM%24&vid=0&q=JTEHT05J872104130

Fluid was flushed last month and pressures are within correct range. I’m not adding weight, just want to add 1-1.5” of height for now.

 

[GTV]

Fluid was flushed last month and pressures are within correct range. I’m not adding weight, just want to add 1-1.5” of height for now.

Then just use 30mm coil spacers, do a sensor lift and readjust the torsion bars to re-correct the pressures.

 

[2001LC]

A common misconception. 30mm spacer on OEM coils, will work with sensor lift. IT WILL NOT! Doing a sensor lift with that configuration. Pressure will be to high. Life of globes will be greatly reduce and ride will not be good as it should. High pressure = blown globes and or shock leaks.

You must use King AHC coils. Kings and 10mm or 20mm (play with thickness, to get best pressure) spacers (donuts), with full sensor lift at stock weight. Yields about 5,6 Mpa rear, once system tweaked. Teak, by raising front with sensor lift, to get proper rake of about 3/4" or greater (front lower than rear). Then adjust front pressure with T-bars to 6.9Mpa. Perfect!

 

[ProvLC]

So i had all 4 globes replaced in the TLC i purchased. Mechanic says that the "AHC is good to go". I bought the truck out of TX and im in the Northeast, Im having my brother who is local, go check out to verify the work..... Is there something i can have him check visually or a process to have him do onsite to confirm it was done properly?

Also, hypothetically. If he did install the (4) new globes and installed new AHC fluid and the pressures are wrong...Am i going have to have new AHC fluid installed to set the pressures to where they should be?

 

[Brett19648]

I’m clearly no expert, but there’s a good YouTube walkthrough I watched. Seems like a pretty straight forward process. The AHC fluid is drained out of the system in the process of replacing the accumulator globes so if the globes were changed the fluid should be new.

If the globes and fluid are new and everything is working properly you should see 10+ bars of change in the AHC fluid reservoir tank when going from the Low to High setting.

For reference mine has original accumulator globes and only gets 4-5 bars when going from low to high.

please correct me if any of that is not accurate.

 

[Brett19648]

A common misconception. 30mm spacer on OEM coils, will work with sensor lift. IT WILL NOT! Doing a sensor lift with that configuration. Pressure will be to high. Life of globes will be greatly reduce and ride will not be good as it should. High pressure = blown globes and or shock leaks.

You must use King AHC coils. Kings and 10mm or 20mm (play with thickness, to get best pressure) spacers (donuts), with full sensor lift at stock weight. Yields about 5,6 Mpa rear, once system tweaked. Teak, by raising front with sensor lift, to get proper rake of about 3/4" or greater (front lower than rear). Then adjust front pressure with T-bars to 6.9Mpa. Perfect!

So if I’m considering the sensor lift and want to retain normal AHC function all I’d have to do is do the shock spacers, then adjust torsion bars?

going with the king springs or a spring spacer is only if I’m adding a lot of weight?

 

[2001LC]

No need to do anything to hydraulic rams (AHA shocks). When doing sensor lift in AHC system. Coil spacers (poly donuts). Sit on top coils (springs)

 

[Brett19648]

No need to do anything to hydraulic rams (AHA shocks). When doing sensor lift in AHC system. Coil spacers (poly donuts). Sit on top coils (springs)

View attachment 4040124View attachment 4040123

So this shock spacer kit that specifically says it’s intended for a sensor lift is not recommended?

 

[GTV]

For 1-1.5” lift there is no need for shock spacers. Just use 30mm coil spacers.

 

[2001LC]

First off. I'm not a builder. I'm a stock guy. I have built on request and modified when need or ask too. Off-road guys have much better handle on this stuff than I. I focuses on baseline. Getting our aging fleet, back to factory reliability. To often I see rigs with tone of money spent on looks and toys, first. When mechanically sounds, needs to be first.

I've no experience with the shock spacer. In theory sound good. Stock height, rams allow for H while driving up to ~19 MPH around town. When off-road, and gear down for crawling on rocks. AHC will stay in H, up to ~35MPH, over that, will come down half way between H & N. Also while in off-road mode, if systems (wh speed sensors) senses your stuck. It will go into hyper high mode. Freaky to see hyper high. Perhaps the shock extenders, would make a difference in hyper. IDK! You'd need to root around in mud, online and talk with Cruiser Patch. See if anyone has actually measured Ram extension vs sensor lift. But keep in mind. Sensor lift, is limited to length of slot in slide of rear adjustor.

It also depends on why you're lift and for what purpose.

• Cool look DD, occasional off road camping/adventure. Not likely, to ever see hyper mode.
• Fender large tire clearance. Not likely, to ever see hyper mode.
• Off-road ground clearance, crawling over rocks. Hyper mode, may come up.

Understand, also. As we change configuration away from factory stock. We change PM schedule needs, wear, alignment and handle. We increase cost of owner ship:

• Need to shorten PM schedule for wheel bearing service. To ~25k miles.
• Increase angle on FDS (AKA CV). Result in older nicely broken-in at factory high, inner CV tulip wear/failure//clicking.
• Center of gravity raised, resulting in increase chance of roll less angle. We can add wheel spacer and or greater off- set wheel, to compensate. But then we need to short wheel bearing service even more. Some feel, rear axle bearing failure sooner. Then we expose side of body paint to rock. As does removing running boards.
• Alignment changes, needs compensation in some with aftmkt UCA.

 

[feelgoodbags]

So i had all 4 globes replaced in the TLC i purchased. Mechanic says that the "AHC is good to go". I bought the truck out of TX and im in the Northeast, Im having my brother who is local, go check out to verify the work..... Is there something i can have him check visually or a process to have him do onsite to confirm it was done properly?

Also, hypothetically. If he did install the (4) new globes and installed new AHC fluid and the pressures are wrong...Am i going have to have new AHC fluid installed to set the pressures to where they should be?

I would start here. ABCs of AHC

The gradation test would be helpful and trying to confirm the globes are oem. I would ask where the globes were purchased. Also, he should test low and high and make sure it's not bouncy when driving.

 

[jaewastooshort]

So this shock spacer kit that specifically says it’s intended for a sensor lift is not recommended?

View attachment 4040170

highly recommended...

the AHC system is give/take between mechanical springs and hydraulic pressure to set/maintain ride height. at the normal setting, there is a specified pressure range that is optimum for the AHC system. when you raise to "high", operating pressure will be much higher, and you are also losing down-stroke in the hydraulic strut. for temporary operation, probably not a huge thing, but if you're looking to do any off-roading, you want the hydraulic strut to be right in the middle of normal operation so you have full stroke up (compression) and down (droop). if you try to do a sensor lift without doing the shock spacers you'll be constantly operating with lower available droop.

Those shock spacers will physically move the bottom mounting point of the hydraulic strut up by (x) amount allowing the vehicle to ride higher while maintaining the AHC shock in the optimum stroke range (basically making the shock positioned like "N" when the vehicle sits like "H").

The most "correct" way to lift while retaining AHC seems to be:
- install the Japan 4x4 shock spacers
- adjust the height sensors
- address the springs to provide the correct load compensation at the new height (pressures back in-spec)
-- maybe the torsion bars can be adjusted enough, maybe they need to be re-splined or changed out
-- OEM rear coil springs will likely need to be replaced, possibly with the addition of a spring spacer
- install a front differential drop bracket to bring the CV axles back closer to the stock angle

might also need UCA's designed to correct geometry when lifted (I got some Dobinson's), and might need extended sway bar links as well