AHC Rear Sag with Added Weight (2 Viewers)

[906KruzaK]

Hey all, this is my first post here, so apologies if this is posted in the wrong place!

Last summer I noticed that my rear end will sometimes automatically adjust itself down to Low, especially when going on more aggressive trails and packed with camping gear, RTT and people. So far, I have been able to get it back into normal, but it often flashes and takes multiple attempts. My LX has a whole lot of added weight, between a steel front bumper, dual swingout steel rear bumper with a 35" spare, and a very heavy CVT Roof Top Tent.

My question is, is this the AHC begging for mercy with the added weight, and if so, what is the best route to go about keeping the rear suspension up and happy with carrying a fully loaded vehicle? I know that some people will add a rear coil spacer to compensate for the added weight, or replace the entire spring with one made for more weight (King coils, Non-AHC LC springs) I also have a set of 13B medium load rear coils from Iron Man, would that absolutely confuse the AHC and cause even more problems?

I have an AHC sensor lift, paired with TB's from the Iron Man Foam Cell Pro kit (done by previous owner, I also have the rest of the kit in boxes still)
It appears that the rear springs are OE

Any information would be greatly appreciated!

 

[zipdoa]

OEM 100 series (2UZ) non-ahc springs - You will exceed GVWR before you lose the ability to go into HI with these
OEM 100 series (2uz) non-ahc torsions - perfect if you're running a heavy bumper + winch

Anything that provides more load capacity than OEM non-ahc suspension will require you to greatly exceed GVWR to get into proper AHC pressures again.

Have you manually calibrated ride height, set calibrated the height sensors to 0 and reviewed pressures in techstream?

I don't really care for the 'AHC lift' since it doesn't actually provide any benefit over running the truck in HI, IMO. But that's why I run 33.2" tires. Can you articulate fully without rubbing on 35's?

 

[Jack90210]

When the AHC pressures get too high, the system goes into "overload" and drops down to Low.

The best route is to 1) read the pressures in order to 2) bring the system back into spec by 3) selecting an appropriate spring (and/or spacers/airbags) for the weight.

Edited to add that this is an informative post about spring rates: Updating AHC system

 

[hoser]

In short, in the rear, you need stock/non-AHC 80/100/200 rear springs and probably 30mm spacers. Don't use aftermarket rear springs (excluding Kings). Then, you need a way to read AHC pressure and adjust accordingly. Your load is typical and learning about modding the AHC system will be to your benefit.

 

[906KruzaK]

OEM 100 series (2UZ) non-ahc springs - You will exceed GVWR before you lose the ability to go into HI with these
OEM 100 series (2uz) non-ahc torsions - perfect if you're running a heavy bumper + winch

Anything that provides more load capacity than OEM non-ahc suspension will require you to greatly exceed GVWR to get into proper AHC pressures again.

Have you manually calibrated ride height, set calibrated the height sensors to 0 and reviewed pressures in techstream?

I don't really care for the 'AHC lift' since it doesn't actually provide any benefit over running the truck in HI, IMO. But that's why I run 33.2" tires. Can you articulate fully without rubbing on 35's?

I have not calibrated ride height, although each corner measures in at nearly the exact same height, front and rear. I'm not sure if the previous owner messed with AHC pressures in the past, and I don't want to assume anything either. I know this also doesn't tell me the pressures are in spec, either. Upon reading more users reply's, I will have to consider purchasing techstream, or just installing the foamcell 2" that i have anyways, I'm with you, an AHC lift is silly.

As for articulation, my tires are more specifically 34.83x11.22, not 35x12.5, and I have had no issues with tucking into the wheel well. Granted, I still have front sway bars and rarely max it out.

 

[906KruzaK]

When the AHC pressures get too high, the system goes into "overload" and drops down to Low.

The best route is to 1) read the pressures in order to 2) bring the system back into spec by 3) selecting an appropriate spring (and/or spacers/airbags) for the weight.

Edited to add that this is an informative post about spring rates: Updating AHC system

Thanks for the info, maybe ill bite the bullet on techstream

 

[shane431]

King springs and a rear coil spacer if needed.

Coil Spacers

Enhance your vehicle's suspension with Ironman 4x4 coil spacers. Elevate ride height, durability, and handling. Ideal for Toyota, Ford, Nissan, Lexus, and more.

www.ironman4x4.com

 

[Jack90210]

Thanks for the info, maybe ill bite the bullet on techstream

All you need to buy is the cable.

How-To: TechStream In 5 Minutes

 

[zipdoa]

I have not calibrated ride height, although each corner measures in at nearly the exact same height, front and rear. I'm not sure if the previous owner messed with AHC pressures in the past, and I don't want to assume anything either. I know this also doesn't tell me the pressures are in spec, either. Upon reading more users reply's, I will have to consider purchasing techstream, or just installing the foamcell 2" that i have anyways, I'm with you, an AHC lift is silly.

As for articulation, my tires are more specifically 34.83x11.22, not 35x12.5, and I have had no issues with tucking into the wheel well. Granted, I still have front sway bars and rarely max it out.

AHC lift is silly, but AHC is worth keeping.

I would recommend calibrating back to factory ride height (which needs to be set with AHC off) and running OEM non-AHC torsions and springs. Anything above that (OME, Ironman etc) will provide too much ‘lift’ and you won’t be able to get into spec with pressures. Not at anything near GVWR.

How heavy is your truck?

 

[906KruzaK]

AHC lift is silly, but AHC is worth keeping.

I would recommend calibrating back to factory ride height (which needs to be set with AHC off) and running OEM non-AHC torsions and springs. Anything above that (OME, Ironman etc) will provide too much ‘lift’ and you won’t be able to get into spec with pressures. Not at anything near GVWR.

How heavy is your truck?

I haven't weighed it yet, but that's something I could even do tomorrow at a nearby station. Coming from a v8 4th gen 4runner, this thing is a tank, and it quite literally feels like it weighs about that as well! AHC lift was done by moving the sensors to max height position, are you recommending me to move them back to center point? GVWR is a new concept to me, what exactly does this mean in this situation?

 

[hoser]

AHC lift is silly, but AHC is worth keeping.

Why is AHC lift silly?

 

[David310]

AHC isn’t able to handle the full weight and transfers it to the springs when in low mode. You need to figure out if your load is static or dynamic.

If the load is static, upgrade to heavier-duty springs like AHC Land Cruiser springs, Kings, or non-AHC Land Cruiser coils. Some people also add spacers to help carry the weight.

If the load is dynamic, such as towing or frequently changing cargo, air bags may work better since you can adjust the pressure as needed.

My current setup is AHC Land Cruiser springs, 30mm Slee spacers, and air bags. I run 15 psi when carrying camping gear and passengers, and 30 psi when towing.

Future setup will be non-AHC Land Cruiser springs with air bags, since I’m adding a rear steel bumper with dual swing-outs.

TechStream is important for checking AHC pressures and fine-tuning the system. Many people switch to conventional suspension because they don’t want to deal with the setup, don’t understand how to get it dialed in, or lines are completed rusted it out and not worth the money. It takes trial and error, but the results are worth it.