I was hoping that wouldn't happen

[ndcruiser]

So, I got the winch on the previously existing Sahara, and the AHC leveled to .5" lower than it was without it.

I had done some reading in the past about weight and the AHC, because I was afraid of messing it up. I know there's some discussion on the forum about it, and I'm currently trying to find a solution that's not digging me even deeper into mods.

Now, it won't go into High. The back does, the front tries, and moves, but just doesn't seem to get to where it wants to, so it defaults back to Normal.

Is this just an adjustment of the new normal? A re-zeroing of some sort?

I'm getting sliders and a rear bumper from Christo, so I'm sure that won't help matters either.

Help! My dealership won't know a thing. Mine is the only AHC vehicle they've ever had.

 

[ndcruiser]

from dinibili's post in May:

If you have one of these vehicles and get a front bar on it, don’t let the installer dick with the torsion bars. When mine was installed they reset them. However, I assume that they started the vehicle before they did. If they did that, the vehicle would have self levelled, and thus any adjustment would have been useless. Mine were adjusted but when the pressures were subsequently checked in the AHC system they were 50% over where they should have been. They need to be set at 6.9MPA +/- 0.5 MPA. Mine were 10MPA.
The vehicle weighs 2.92T total with 1.54T in the front and 1.40T in the rear. Doesn’t quite add up I know, but the wind was blowing when it was weighed.
The pressures are reset by screwing the adjusting nuts on the TBs such that every full turn on both sides alters the pressure by +/-0.2.MPA depending on which way you turn them. Measuring the pressures is easiest done by Lexus or Toyota as they just plug a service device into an electrical plug under the dash and read off directly indirectly. You can measure them yourself by accessing the bleed plugs under the vehicle. There is a procedure for this, which I won’t bore you with. The pressures for bleeder plug reading are in fact about 1.2MPA less than reading them from under the dash.
The addition of the rear bar (105kgs) raised the pressures in the rear to 8.5 MPA. They should have been about 6.5MPA (if fitted with sub tank). Reading the pressures at the bleeder plugs will again be about 1.2MPA less.
The rear coils don’t allow such an easy solution as the TBs. Thus the airbags.
My next step is to get the vehicle to a Lexus dealer so that I can accurately match the air pressure to the AHC pressure for the two driving situations, normal every day base load and extra loaded for travelling. Under each scenario I will set the psi such that the AHC pressure is where it should be. 6.9MPA front and 6.5MPA in the rear. The reason for using a Lexus dealer is to avoid the lectures & crap from the Toyota people and keep out of their black book.


Is this the consensus? And should I have the dealership do it? Is it in their FSM somewhere? I don't want to confuse them more than they already are.

 

[uHu]

Is this the consensus? And should I have the dealership do it? Is it in their FSM somewhere? I don't want to confuse them more than they already are.

Yes, it's in their FSM.
If you are not doing it yourself, according to this procedure:
https://forum.ih8mud.com/showpost.php?p=858169&postcount=11
, then let an experienced AHC tech do it.
Even though the procedure is well described in the FSM, it's not good enough if you don't understand the AHC (design and function).

 

[xlr8it]

I had same problem on my LX470, it has a sahara bar and warn winch, I took the LX to my local Lexus dealer and they set the torsion bars to correct levels and adjusted the height sensors , NO more problems, works like new again, they also replaced my AHC fluid at the same time and the whole job cost me only AU$100 including a Lexus loan car for the day. Bargain I think.

 

[ndcruiser]

good. I feel better now.

Should I wait to take it in until after I get the sliders and rear bumper on? I know, its not nearly as heavy as the front.

I have 12K miles on, should I change the AHC fluid?

Also, Christo had mentioned something about needing new torsion bars. How do I know if that's necessary?

Thanks-

 

[xlr8it]

You do not need to change the fluid until you hit 60k miles, I would wait until you have all your accessories on and then get them adjusted.I think you only need to change the Torsion Bars if they can not be adjusted far enough, but mine were fine and I have a rear Kaymar bar with a spare carrier on it as well as the Sahara and a winch on the front.

 

[ndcruiser]

At the dealership right now. It took awhile to figure out what's going on. It was in the FSM, and I showed them the post on this site.

He said he had had to work on a LX with AHC.........once.

Slee seems to think I will need new, stiffer torsion bars. Hopefully the adjustment route works.

 

[ndcruiser]

Well, first answer back is that the system was low on fluid, and they didn't have any so, I won't know for a few more days.......

Could that be the reason that it didn't work in the beginning?

 

[xlr8it]

It would have to be very low on fluid for it not to work, and then you would get air in the system and it would have to be bled, so i do not think that it is the problem.

 

[ndcruiser]

"it was low on fluid" probably means the guy was messing around with it and leaked some.

I'm going to pick it up in a few minutes. Wanna bet its in Low when I get there!


"The only enemy of Good is Better", a surgeon friend told me once.

 

[ndcruiser]

Well, just for those who may someday deal with the same thing:

I finally got it to work by adjusting the torsion bars up two turns. But I already had the heavy ones coming from Christo, so I decided to put them in.

The mechanic sheared off the 22mm (or something like that) bolt, and I was dead in the water for a week while we got the only one from Toyota in North America.

Put the other heavy TB in, and cranked it up to the original measurement (wheel well height) and it rode terrible. No dampening. Figured that the AHC wasn't being loaded at all, and when I went to L, the rear lowered, but the front didn't.

So, after loosening the TB's, 2 turns at a time, at 4 turns looser it finally works well. It goes into H, and L, I wasn't sure that it would.

Christo was very helpful and fielded a bunch of "what now" questions from me. Great customer service.

Oh, I did put his bumper on (without tire carrier) and I'm impressed with the engineering. Absolutely pitiful to compare the stock bumper to it.

Hopefully this can of worms is now over. Oh, finally got an explanation on the "low fluid" comment from the dealership - they were anticipating needing to add fluid, they didn't even mess with it, nor did I do any adjustment to the AHC.

 

[xlr8it]

John,
I am glad it finaly worked out for you.

Cheers
Leon

 

[CrusrDug]

ndcruiser-

How was the ride with the original torsion bars cranked up? Did the AHC operate as before? Have you had any pressures checked on the AHC system?

Also, what happened when you put the heavier rear bumper on. Did it just self level? Again, have you checked the pressures to bring it back to stock?

Got any before and after pics? Would like to see them since I have an 06 as well.

Did the stealer give you grief for messing with a vehicle still under warranty?

thanks

 

[ndcruiser]

Crusrdug

Will take pics when I get the sliders this week, I think it looks a little neutered without them (took the running boards off last week).

To be honest, the ride seemed fine with the stock TB's cranked up 2x. The reasons I went for the switch are:

1) Christo had already sent the new bars
2) The concept of the stiffer bars having better performance (stiffer over a longer range rather than stiffer over shorter range of activation because they've been twisted tighter) made sense to me, and I'm always ready to make it better.
3) Thought it was going to be simple

I learned AGAIN, that "the only enemy of good is better".

Its all subjective of course, but I think the ride might be better now than originally. I thought I noticed the ride deteriorate slightly from the Sahara bumper, but tried to forget about it.

The rear didn't budge it at all. Makes sense though, the rear should handle more. The tow bar is a pretty solid piece of box steel, I was surprised how heavy it was.

 

[ndcruiser]

Forgot - no, dealership didn't mention it at all. Seemed a little dumbfounded about it all. Remember, a LC under warranty is pretty rare around here.

 

[Jim_Chow]

BTW, the FSM says to adjust the t-bars until the front AHC pressure is within the spec'd range. It gives an approximation of how much the pressure changes for 1 turn of the t-bar bolt (can't remember the value off the top of my head, though). So I don't think you need new t-bars as you found out.