AHC wont go into high

[razzyrazz]

Since I put my front bumper and winch on along with doing the sensor lift a couple years ago, my LX won't go into high. The rear end moves up to high and the front goes up, but apparently not high enough to register as high on the dashboard.

Took bumper and winch off yesterday to replace the winch cable and tested without the extra weight. LX went high enough to officially get into high. Truck has 105k miles, any numbers I can check in techstream to see if the pump is weak or could it be remedied with some fresh shocks or springs to help the AHC lift the extra weight?

 

[TeCKis300]

The system has sensors to make sure it doesn't exceed built in hydraulic pressure thresholds. It's not a factor of a weak pump, you're just exceeding what the system is built to do.

That said, there's solutions. What's happening with a large sensor lift is that the hydraulic portion of the suspension is asked to carry more than it's fair share of weight. With the physical coil springs carrying less. Add in heavy accessories, and it'll exceed the pressure threshold.

What you need to do is pre-load the coil springs with spacers so that its carrying it's fair share of weight at the higher lifts. Short answer is install the OEM LC leveling spacer to the front. Install 20-30mm of spring spacers to the rear, or airbags, or both.

Find more detail in my build thread under suspension here:

Builds - TeCKis300 LX570 "FLX" Build

Updated 9/24/2024 - Latest build on 37s Stock on 31s, then 33s, 35s, and now what feels like build v37 of Flexus on 37s. Can't leave well enough alone and it's an itch that must be scratched. Previous build on 35s - Builds - TeCKis300 LX570 "FLX" Build -...

forum.ih8mud.com

 

[grinchy]

There are also uprated ahc springs available from terrain tamer for the rear as an additional option.

 

[teejnut]

I had a similar issue. All fixed by installing the Toyota front spacer and switching to the Terrain Tamer rear springs.

 

[radman]

Just curious, which bumper do you have on there? A big steel one?

 

[razzyrazz]

Just curious, which bumper do you have on there? A big steel one?

Dobinson front bumper and an 80 lb. Winch.

 

[SF1911A1]

I have an Ironman front bumper, sliders and full set of skids. Have not installed the winch yet but I’m also a little worried about overloading the AHC. Does installing the spacer mess up the caster or not enough to matter?

 

[bloc]

I have an Ironman front bumper, sliders and full set of skids. Have not installed the winch yet but I’m also a little worried about overloading the AHC. Does installing the spacer mess up the caster or not enough to matter?

The only way it would impact alignment is from having to remove the strut assembly to actually install it. Beyond that caster changes are dependent on ride height.. with AHC if the spacer simply adds coil spring pressure and the hydraulic system adjusts things for the same ride height as before, there won't be a caster change.

But having to loosen the cam bolts on the LCA will likely impact camber, caster, and toe.

 

[SF1911A1]

The only way it would impact alignment is from having to remove the strut assembly to actually install it. Beyond that caster changes are dependent on ride height.. with AHC if the spacer simply adds coil spring pressure and the hydraulic system adjusts things for the same ride height as before, there won't be a caster change.

But having to loosen the cam bolts on the LCA will likely impact camber, caster, and toe.

That makes sense, so just get an alignment afterward and I should be good to go. I have 127k miles, should I replace anything while I’m in there?

 

[bloc]

That makes sense, so just get an alignment afterward and I should be good to go. I have 127k miles, should I replace anything while I’m in there?

Check for upper and lower ball joint play while you will have it apart, same for tie rod end. They are pretty robust though and that mileage usually isn’t a problem unless there was an impact of some kind to that corner.

 

[tbisaacs]

I have an Ironman front bumper, sliders and full set of skids. Have not installed the winch yet but I’m also a little worried about overloading the AHC. Does installing the spacer mess up the caster or not enough to matter?

FWIW, my AHC is not overloaded. It would benefit from heavier spring rate more preload (via spacer) up front though.

 

[bloc]

I’m getting into semantics, I know, but technically the spacers don’t add spring rate, they add preload.

The true fix for this would actually be an appropriately higher rate spring.

The spacer does add down travel though, with obvious benefits. A higher rate spring wouldn’t.

 

[tbisaacs]

I’m getting into semantics, I know, but technically the spacers don’t add spring rate, they add preload.

The true fix for this would actually be an appropriately higher rate spring.

The spacer does add down travel though, with obvious benefits. A higher rate spring wouldn’t.

I get ya. Corrected

 

[SF1911A1]

FWIW, my AHC is not overloaded. It would benefit from heavier spring rate more preload (via spacer) up front though.

That makes me feel a little better but I’m still going to order the levelers for the front before I put the winch in. Thanks for the input.

 

[highfructose]

Has anyone actually installed the front spacers?

I’ve purchased them, along with 2021 front coils (which are different part number than pre 2016), but have not yet installed.

 

[TeCKis300]

The only way it would impact alignment is from having to remove the strut assembly to actually install it. Beyond that caster changes are dependent on ride height.. with AHC if the spacer simply adds coil spring pressure and the hydraulic system adjusts things for the same ride height as before, there won't be a caster change.

But having to loosen the cam bolts on the LCA will likely impact camber, caster, and toe.

Talking about semantics, and this one may be a bit debatable because of how loosely the market uses it, and has misinterpreted it.

Struts are by design part of the suspension structure and take side loads. The coilover shocks in cruisers only bear weight. In our suspensions, the shock assembly only bears weight so that's what they are.

 

[TeCKis300]

Has anyone actually installed the front spacers?

I’ve purchased them, along with 2021 front coils (which are different part number than pre 2016), but have not yet installed.

Yes, look here - OEM Front Spacer Install for AHC Suspension - https://forum.ih8mud.com/threads/oem-front-spacer-install-for-ahc-suspension.1188916/

At the risk of complicating this discussion, I just did a once over again on my setup and took this further with an LC spacer (10mm) stacked with an aftermarket (6mm) spacer. To get more 1.5" more suspension travel over stock. May not be worth the trouble for most as it's way more work than just dropping in the LC spacer, which is the solution for the intent of this thread.

 

[bloc]

Talking about semantics, and this one may be a bit debatable because of how loosely the market uses it, and has misinterpreted it.

Struts are by design part of the suspension structure and take side loads. The coilover shocks in cruisers only bear weight. In our suspensions, the shock assembly only bears weight so that's what they are.

Agree that it’s debatable but I still view what we have as struts.

One thing the industry seems to agree on is a shock is a single component, and a strut combines multiple components into one assembly. Everyone here knows the spring is on the front damper.. the spring is integral and can’t do its job of supporting the vehicle without being on the strut.

Whereas on the back (or any true shock application) if you remove the shock you can still drive down the road.. though you AHC guys blur the line by sitting on bump stops if you do. but on a regular coil 200 the only job of the rear shock driving down the road is for damping. It does limit travel in severe off-road terrain but this doesn’t seem within the scope of what the industry is thinking about when coming up with these labels.

Our front struts aren’t as integral to the vehicle going down the road as those on a McPherson strut vehicle, for sure. But they still fit the definition of strut that seems to be the consensus in the industry.

I do admit the terms are very widely interchanged.. but if anyone hasn’t figured out yet, I’m kind of a stickler for precision when it’s available. IMO it helps us understand each other better, and can make these often complex mechanical ideas easier to learn about and understand.

 

[TeCKis300]

Agree that it’s debatable but I still view what we have as struts.

One thing the industry seems to agree on is a shock is a single component, and a strut combines multiple components into one assembly. Everyone here knows the spring is on the front damper.. the spring is integral and can’t do its job of supporting the vehicle without being on the strut.

Whereas on the back (or any true shock application) if you remove the shock you can still drive down the road.. though you AHC guys blur the line by sitting on bump stops if you do. but on a regular coil 200 the only job of the rear shock driving down the road is for damping. It does limit travel in severe off-road terrain but this doesn’t seem within the scope of what the industry is thinking about when coming up with these labels.

Our front struts aren’t as integral to the vehicle going down the road as those on a McPherson strut vehicle, for sure. But they still fit the definition of strut that seems to be the consensus in the industry.

I do admit the terms are very widely interchanged.. but if anyone hasn’t figured out yet, I’m kind of a stickler for precision when it’s available. IMO it helps us understand each other better, and can make these often complex mechanical ideas easier to learn about and understand.

The aftermarket has butchered the definition. In engineering terms, it's very specific. It has nothing to do with the assembly. It's about the purpose of the shock itself - whether it serves damping only, or has to handle damping and side loads.

I'd encourage you to research real sources like shock OEMs, or our manual. Not the aftermarket sales outlets.

Toyota never references anything to do with struts for the Land Cruiser, because it does not use them as part of the lateral load architecture.

Our front shocks are referenced in the manual as just that, "shock', even though the spring is co-located with the assembly. Our rears separate out the spring from the shock and it's still referenced as a shock.

Versus something like a Camry or ES300, those clearly are referenced as struts because the damper component also serves as the upper lateral suspension link.

 

[bloc]

The aftermarket has butchered the definition. In engineering terms, it's very specific. It has nothing to do with the assembly. It's about the purpose of the shock itself - whether it serves damping only, or has to handle damping and side loads.

I'd encourage you to research real sources like shock OEMs, or our manual. Not the aftermarket sales outlets.

Toyota never references anything to do with struts for the Land Cruiser, because it does not use them as part of the lateral load architecture.

Our front shocks are referenced in the manual as just that, "shock', even though the spring is co-located with the assembly. Our rears separate out the spring from the shock and it's still referenced as a shock.

Versus something like a Camry or ES300, those clearly are referenced as struts because the damper component also serves as the upper lateral suspension link.

I may be able to keep this in mind with online discussion but after almost 30 years of wrenching on and reading about cars among an industry that apparently has their terminology wrong, my conceptual understanding is unlikely to change. Old dog, new tricks. Or whatever phrase is appropriate.