I LOVE my AHC. (1 Viewer)

[pman]

That's just the thing. There is no high end anything that is as effective across as broad of a spectrum as AHC - hence my enthusiasm. You can get higher load carrying or more high speed washboard handling with an aftermarket setup, but always at the detriment of other use cases.

I hear you on the KISS. Though that's somewhat of an interesting concept when applied to the tour de force of the Hundy, which has other high end sophisticated systems such as the electric brake booster, VGRS, etc. I trust Toyota to walk the fine line between too much complexity at the cost of reliability and durability, which I feel the Hundy does with aplomb. At a cost. Though I knew this going in which is okay with me.

IDK if you have ever driven anything with high end remote res shocks that are properly tuned, but it is very impressive what it will do to the way a vehicle rides and handles.

Personally, Im not a fan of how AHC handles the weight of the vehicle in some situations....doesnt have the valving to keep it from wallowing around.

As for KISS, the stuff you listed is going to be there on any newer vehicle. Electric brake boosters have been around a while and are necessary these days. ATRAC, ABS, EBD, and all that other kind of stuff are mostly software and a few sensors.

AHC is different because it is a mechanical load bearing system with moving parts that are constantly being worked. Once it fails you are essentially stuck, there is no limping home when AHC dies, unless you want to risk damaging your truck more. Plus the way i look at it is, in the rest of the world, where these vehicles are used as Toyota intended them to be used, very very few of them have AHC.

 

[agaisin]

Sanity check - are people overreacting about what happens if AHC 'fails'? I guess there are different modes of failure, but I'm imagining either one or more globes fail/rupture or the hydraulic fluid leaks. Certainly if the globes fail that's not going to keep you from limping home. Even if the hydraulic fluid leaks out completely, I have to believe you'd be able to limp home as well? Does anyone have reason to believe otherwise?

Regarding the electronics, according to the FSM design doc on the suspension, there's a failsafe mode so that "If a malfunction occurs in any of the sensors or actuator, the ECU prohibits the vehicle height control and the damping force control."

 

[agaisin]

Here's some official snippets from FSM documentation on the height control ->

During Lo Position:
When the vehicle speed becomes
higher than approximately
5 km/h (3 mph), the vehicle
height transfers to normal.
The normal vehicle height is
maintained even if the vehicle
speed becomes lower than 5
km/h (3 mph).

"During Hi Position":
When the vehicle speed becomes
higher than approximately
30 km/h (19 mph), the vehicle
height transfers to normal. The
normal vehicle height is maintained
even if the vehicle speed
becomes lower than 30 km/h (19
mph).

"During Hi Position with Transfer shifted in Low":
When the vehicle speed becomes
higher than approximately
50 km/h (31 mph), the vehicle
height transfers to a height that is
approximately 25 mm (1 in.)
higher than the normal vehicle
height. When the vehicle speed
becomes lower than approximately
20 km/h (12.5 mph), it
returns to the high vehicle
height.

Also on the topic of what the system does other than height control and explicit setting of the damping switch:
2) Thumping Sensitive Control
When the road surface condition does not require a damping force, this function controls the actuator
so that their damping force will not increase.
As a result, both flatness and a soft ride have been achieved.
3) Unsprung Vibration Control
If unsprung resonance is detected, this function controls so that the damping force will not decrease
below a certain level, in order to reduce the unsprung resonance.
As a result, excellent road-holding performance has been ensured without affecting riding comfort.

4) Speed Sensitive Control
To optimally balance the vehicle’s riding comfort and road-holding performance, the damping force is
increased along with the increase in vehicle speed, in order to ensure stability during high-speed driving.
5) Anti-Roll Control
During cornering, this function makes the damping force firmer, thus restrating the body roll speed in
order to provide excellent stability and controllability.
6) Anti-Dive Control
During braking, this function makes the damping force firmer to restrain the body dive, thus ensuring
excellent stability and controllability.
7) Anti-Squat Control
During acceleration, this function makes the damping force firmer to minimize the changes in the vehicle
body posture to provide excellent stability and controllability.
8) Damping Force Control
The actuator uses a 16-step step motor to generate a continually variable damping force. This provides
a wide selection of damping force and enables a smooth transition of the damping force.
As a result, a minutely controlled damping force that accommodates various types of driving conditions
has been made possible.

"Right-Left Wheel Communicating Function"
Normally, an oil passage remains open between the shock absorbers for the right and left wheels. This
enables the suspension to contract and elongate smoothly when the right and left wheels move gradually
at opposite phases and provides excellent road-holding performance while driving on a winding road.
When the driver operates the steering wheel, the oil passage between the right and left shock absorbers
closes according to that condition. This restrains the increase of the vehicle body roll during cornering,
thus ensuring the vehicle’s stability and controllability.

 

[sonk76]

Here's some official snippets from FSM documentation on the height control ->

During Lo Position:
When the vehicle speed becomes
higher than approximately
5 km/h (3 mph), the vehicle
height transfers to normal.
The normal vehicle height is
maintained even if the vehicle
speed becomes lower than 5
km/h (3 mph).

"During Hi Position":
When the vehicle speed becomes
higher than approximately
30 km/h (19 mph), the vehicle
height transfers to normal. The
normal vehicle height is maintained
even if the vehicle speed
becomes lower than 30 km/h (19
mph).

"During Hi Position with Transfer shifted in Low":
When the vehicle speed becomes
higher than approximately
50 km/h (31 mph), the vehicle
height transfers to a height that is
approximately 25 mm (1 in.)
higher than the normal vehicle
height. When the vehicle speed
becomes lower than approximately
20 km/h (12.5 mph), it
returns to the high vehicle
height.

Also on the topic of what the system does other than height control and explicit setting of the damping switch:
2) Thumping Sensitive Control
When the road surface condition does not require a damping force, this function controls the actuator
so that their damping force will not increase.
As a result, both flatness and a soft ride have been achieved.
3) Unsprung Vibration Control
If unsprung resonance is detected, this function controls so that the damping force will not decrease
below a certain level, in order to reduce the unsprung resonance.
As a result, excellent road-holding performance has been ensured without affecting riding comfort.
4) Speed Sensitive Control
To optimally balance the vehicle’s riding comfort and road-holding performance, the damping force is
increased along with the increase in vehicle speed, in order to ensure stability during high-speed driving.5) Anti-Roll Control
During cornering, this function makes the damping force firmer, thus restrating the body roll speed in
order to provide excellent stability and controllability.
6) Anti-Dive Control
During braking, this function makes the damping force firmer to restrain the body dive, thus ensuring
excellent stability and controllability.
7) Anti-Squat Control
During acceleration, this function makes the damping force firmer to minimize the changes in the vehicle
body posture to provide excellent stability and controllability.
8) Damping Force Control
The actuator uses a 16-step step motor to generate a continually variable damping force. This provides
a wide selection of damping force and enables a smooth transition of the damping force.
As a result, a minutely controlled damping force that accommodates various types of driving conditions
has been made possible.

"Right-Left Wheel Communicating Function"
Normally, an oil passage remains open between the shock absorbers for the right and left wheels. This
enables the suspension to contract and elongate smoothly when the right and left wheels move gradually
at opposite phases and provides excellent road-holding performance while driving on a winding road.
When the driver operates the steering wheel, the oil passage between the right and left shock absorbers
closes according to that condition. This restrains the increase of the vehicle body roll during cornering,
thus ensuring the vehicle’s stability and controllability.

This makes the system sound amazing! I do like it a great deal myself.

I also don't see how a failure of it would be "catastrophic". Worst case scenario seems that you would limp home riding the bump-stops, with minimal shocks. Far from ideal, but something that should get one home... unless I'm missing something.

 

[Yukon LX]

It is not catastrophic, and i think the fans of it here agree, it really is good while it lasts. Its drawback is the cost of replacement. Thus, when it dies, you go to the previously mentioned KISS, or if you want to spend the coin, replace. Until then its great. And the vehicle is most certainly operational with a blown globe, much like you can still drive a truck with a blown shock. The difference between sport and comfort is amazing. Like i said before, comfort is like a caddy on the interstate. Sport is not as firm as most offroad conventional setups, but does more than enough for most applications.

 

[TeCKis300]

IDK if you have ever driven anything with high end remote res shocks that are properly tuned, but it is very impressive what it will do to the way a vehicle rides and handles.

I can't say I have for a truck, but I'm very familiar with high end coilovers in the sports car realm. It sounds like your needs are outside of the stock AHC's performance envelop. Though I think it's more an issue of spring rate than damper valving.

Still, an aftermarket system is a static system with a specific damping curve, setup and optimized for specific weight and aggressive use. It technically cannot touch the breadth allowed for by an active system. While it might have capacity beyond what AHC allows for, it definitely won't be challenging the supple ride quality of AHC - which itself is technically a remote reservoir system with more sophistication.

Sanity check - are people overreacting about what happens if AHC 'fails'? I guess there are different modes of failure, but I'm imagining either one or more globes fail/rupture or the hydraulic fluid leaks. Certainly if the globes fail that's not going to keep you from limping home. Even if the hydraulic fluid leaks out completely, I have to believe you'd be able to limp home as well? Does anyone have reason to believe otherwise?

I do think it is. That and the high cost associated with replacing a wear item that seems to be voodoo to the typical mechanic. AHC does seem to be a durable system otherwise.

The 'catastrophe in a remote location' scenario seems easily accommodated by installing relatively cheap airbags IMO. Or a more expensive strategy of proactive replacement of the wear items.

BTW, thanks for that excellent run down of AHC capabilities. I had not seen that before. And it has real tangible benefits even beyond what I originally understood. Hard to fathom giving up all that real utility.

 

[Wilsil]

The difference between sport and comfort is amazing. Like i said before, comfort is like a caddy on the interstate. Sport is not as firm as most offroad conventional setups, but does more than enough for most applications.

My suspension doesn't change with the settings.
Meaning that it is broken.

I would like to keep the AHC as well, however on one condition: that it can handle the extra weight for long range tank (180 liters), dual spare wheel carrier, fridge, Kimberley Kamper.
As it is now (stock) the AHC doesn't even handle it when I hook up the KK, even when it isn't fully loaded.

 

[MilkmanVX]

My suspension doesn't change with the settings.
Meaning that it is broken.

I would like to keep the AHC as well, however on one condition: that it can handle the extra weight for long range tank (180 liters), dual spare wheel carrier, fridge, Kimberley Kamper.
As it is now (stock) the AHC doesn't even handle it when I hook up the KK, even when it isn't fully loaded.

It's all about a little compromise. If you are going to add that much weight to your vehicle -strip out the AHC (or add airbags like some have done). If you don't camp out with your all your belongings .. then you should be just fine.

One more thing on the AHC, I have noticed that when I do a quick run on bumpy/rough stuff -even without my raising the car, it automatically rides slightly higher (this I notice when I come to a stop -and lowers within a few seconds after stopping) ... very smart ...

That noted, of course if I did stuff with my car which broke the AHC even on an annual basis, I would definitely swap it out ....

 

[SaadUK]

I have two 100 series and I regret buying them with AHCs. I have spend as much money for what u can buy another 100 series on these pathetic systems. They r so damn complicated even Toyota is confused over it. They can't master the technology which was developed in 1930s. From what I read in this forum, there is absolutely no person who is 100 percent well educated about these systems. Everyone is guessing their ways. Sorry no offence but we need to be straight. Anyhow Toyota should stop cheating andaster themselves in simpler systems rather.

 

[Yukon LX]

that is why you enjoy it while you have it, and when it breaks, bye bye. If you continually pump money into it, to the point of affording another 100, i think there are other issues here.

 

[tabraha]

It is not catastrophic, and i think the fans of it here agree, it really is good while it lasts. Its drawback is the cost of replacement. Thus, when it dies, you go to the previously mentioned KISS, or if you want to spend the coin, replace. Until then its great. And the vehicle is most certainly operational with a blown globe, much like you can still drive a truck with a blown shock. The difference between sport and comfort is amazing. Like i said before, comfort is like a caddy on the interstate. Sport is not as firm as most offroad conventional setups, but does more than enough for most applications.

Sums it up for me. I have no reason to complain even if it craps out tomorrow at 13 years of service and 200k+ miles. I'd easily be on my second or third set of shocks and probably non-OEM springs by now also. This is coming from a guy who uses his as a work truck and gets off-road time in several days a week as God and toyota intended.

 

[sailor95]

Is there anything we can do to make the AHC more durable? I am at 260k miles on my LX and love my height control but need to start thinking of preventive maintanence for it.

 

[Yukon LX]

No. It is what it is. Like i have said many times. ^^^^^^^^^ look up. It is a cool thing when it works, just do not put money into it when it breaks, unless you have it. AHC is your hot girl friend that is so amazing when while you have it. But it will go bad. So go with the non cheatin lady once the whore strays out. This is not a complicated thing.



AHC=================== ok something in it broke=it was cool while it lasted========== YAY, now i get a new suspension, and lift, all around with long lasting components.


But wait,

Thats cool too!!

This is not rocket science

 

[04UZJ100]

Why is there so much hate in this thread? And why is it so hard to believe that someone who can afford to pay 80k for an LX can also pay to have AHC fixed if they choose to do so.

Jesus.

 

[Yukon LX]

Because the best bet all around is triple locked with atrac. The hard thing is to find where the locker v atrac question meets a middle But hardly anyone on this thread paid 80 k for their 100.

I am not Jesus.

I simply post on a forum.

 

[lexi4darin]

Guys some of you should be careful as you're mixing your preferences and desires as tho they are facts or absolutes. They are not facts but instead are your conclusions based on your set of needs/wants/budgets/etc.

The best bet is NOT triple locked, blah, blah. That sounds ignorant of the other aspects the 100 is great at providing. Learn to appreciate and respect all the 100's capabilities and do not ignore its other abilities that are less appealing to your small set of presences.

The AHC system is very very reliable and adds a lot of capability to a stock truck while keeping it drivable for those with real urban needs. A triple quadruple-teen "locked" truck is only the best bet when your needs far exceed the norm in off road use AND you have less needs on road or with mall cruising.

My grandma isn't going to be able to make it up into your quad lifted beast so in fact your truck would be considered less usable to some people.

Respeck.

 

[lexi4darin]

The 'catastrophe in a remote location' scenario seems easily accommodated by installing relatively cheap airbags IMO. Or a more expensive strategy of proactive replacement of the wear items.

BTW, thanks for that excellent run down of AHC capabilities. I had not seen that before. And it has real tangible benefits even beyond what I originally understood. Hard to fathom giving up all that real utility.

Teckis - agreed. And while you're being proactive on maintenance, it wouldn't be that hard to keep and then carry a couple of the old (but still working) globes as spares. They only take a few mins to replace and would definetely limp someone home.

I think the AHC capabilities are listed in the original owners manual.

 

[MilkmanVX]

Is there anything we can do to make the AHC more durable? I am at 260k miles on my LX and love my height control but need to start thinking of preventive maintanence for it.

Yes.

1. Change out the AHC fluid every 100,000Kms or around 60k miles (FSM) -bleed the spheres and accumulator to ensure fresh fluid gets in (instructions on how to are on this forum somewhere). Also check the gas chamber every 12 months (again, FSM)

2. Check your neutral pressure -this indicates if everything is within spec (again, instructions on how to are on this forum somewhere).

3. If you haven't already, get new AHC spec rear springs, at 260k miles I am sure there is some sag in them thus putting more pressure on the AHC system (for front, you just need to crank the Tbars) ....

4. Number 3 should be done after checking out neutral pressure.

5. Check other suspension parts for wear -bushes, UCAs LCAs etc etc etc .... I am sure since your shox have never been changed, the bushes must be well worn, cracked, hardened .....

6. Enjoy your AHC ... use it at every opportunity ...

 

[pman]

. Worst case scenario seems that you would limp home riding the bump-stops, with minimal shocks. Far from ideal, but something that should get one home... unless I'm missing something.

Personally I think driving home on your bumpstops is a terrible idea. Think about it, essentially zero dampening, the majority of the weight on the bumpstops and every bump in the road gets sent straight to the bumpstop/chassis. Also your CVs and other joints will be at their upper limit for movement range ( or close to it) for the entire ride.

Personally I dont want to put that kind of stress on my LCAs, bumpstop mounts and everything else. AHC failure is not like a blowing a shock on a normal truck, the shocks on a truck with AHC are supporting the weight of the vehicle to maintain ride height.

That said failures are rarely sudden, or atleast that seems to be the case and the system is reliable.....


All that said, I will continue to enjoy AHC till the day it dies.

 

[Yukon LX]

^ as far as your first paragraph, there are still springs and T bars, they are just not strong. however, they still take some of the load.