AHC - I really need some help.

[ndcruiser]

OK - I'm having problems, and I don't know how bad I've got it.

#1 problem - I don't have an offroad shop to go to that has any experience with what I'm dealing with.

Story, again.

Put a Sahara bumper on last year = no problems. Ride may have gotten a bit stiffer up front.

Put a winch on last week, vehicle won't go to Hi, but has no problems at Normal height.

I was anticipating this a bit, so I did some reading on it, but although a relatively intelligent dude, I don't quite understand where I need to go from here.

The solutions I'm getting:

1) Replace Torsion bars with stiffer rate ones - this is what Christo did.

2) Toyota dealership doesn't really know whats happening - they say my fluid is low, and had to order some. Have only worked on one AHC before. Think "adjusting the torsion bars" might help.

3) Local shop guy says adjusting the torsion bars should be fine.

Christo says that the spring rate is the issue, not the TB adjustment.

So, the way I understand it is that I not only have a weight problem affecting the AHC level, but also its dampening?

Will the torsion bars alleviate some of the strain on the system, and make the AHC funciont more as normal?

Does the AHC system itself need adjustment? Do I need to reset it to "normal"?

I'm getting different bits and pieces of info, and I just can't get it all together.

My goal, by the way is to just get the system to act as normal with this weight, and the rear bumper and sliders I'm getting. Don't need to get extra lift, etc.

Trying to avoid driving 700 miles to see Christo to get it rectified (especially after I'm spending hundreds on shipping to get the stuff up here!)

Thanks for your thoughts-

 

[tabraha]

John the way I see it is worst case you've got to buy the HD torsion bars. The middle of the road solution would be swapping out to the non-AHC t-bars. They have a slightly higher rate that would probably get you back close to pre-armor specs. The cheapest solution is to try to re-index the t-bars and see what happens. I see no harm in trying that first. IF that doesn't get your AHC back up to snuff then look into changing out the t-bars. As far as using the non-ahc or heavy duty t-bars; let Christo make that call. He knows what his stuff weighs and probably has the best judgement of anyone. No trip to CO necessary but hey, if you want to go for it!

 

[hoser]

I'll give you my thoughts though I wouldn't say I'm an expert on the AHC system. Besides the Toyota engineers, Christo is probably the most knowledgable on this subject--at least around here.

As you know, the suspension system is shared by the springs and AHC components. There is a balance between the two which is measurable. It is possible the balance is biased too much towards the AHC shocks in which case, cranking the T-bars up a little would help. However, with an extra 175lbs or so up front, it might be a good idea to go to the std LC T-bars. If you do, I would suggest you go to a Lexus shop to have those changed out and calibrated since, theoretically, they have 8 more years of experience with the AHC system.

The rear springs/AHC can take the weight of your rear bumper and sliders just fine. But adding another 600 or so pounds of gear, the butt will drop. If you find a problem with load carrying capacity, I'd switch to 80 series OEM rear springs but not before then as 80 series springs and only 300 lbs of extra weight will give a slightly "springy" ride. Not too bad though.

So, to reiterate, have the front suspension recalibrated as per FSM specs. Or you can just crank them up yourself and see what happens. If that doesn't work, swap out the T-bars for standard LC bars. Christo probably has a pair sitting around.

 

[ndcruiser]

Thanks hoser- I appreciate the reply.

The nearest Lex dealer is 450 miles away, but I'm heading down there in a few weeks anyway.

Christo is sending my rear bumper and a used set of front TB's today. I don't think it will make much difference in the rear, because I can carry a big snowblower on an 80lb hitch-haul without problem - haven't tried Hi yet with it though.....

"Calibrated" - is that the pressure adjustment I've read about?

 

[hoser]

"Calibrated" - is that the pressure adjustment I've read about?

Yes, mentioned here if you don't have the FSM.

https://forum.ih8mud.com/showpost.php?p=858169&postcount=11
https://forum.ih8mud.com/showthread.php?t=94903

Using the Toyota Handheld tester, the front suspension should be 6.9 MPa with a tolerance of 0.5 (996 +- 71 PSI) without the extra weight of the bumper/winch. So, with the extra weight, the pressure should read higher but how much higher?... you're in unexplored territory. If you go this route, please let us know your findings. I'm curious if you set it to 996 psi, how the ride would be and if you would retain all the height settings. I need to buy an LSPV gauge.

 

[ndcruiser]

Well,

Torsion bar adjust helped. It works now. Thanks for getting me to try it hoser.

Question is: do I put the other TB's on (already on their way) and open up that can of worms, or is it really unnecessary?

 

[ndcruiser]

Had a good talk with Christo -

I'm going to swap out the torsion bars anyway, because the stiffer ones will perform better with the weight. Kinda like I was referring to earlier, I had a feeling that cranking my height up a bit was more of a Band-Aid fix. However, now I've preloaded the torsion bars, and the dynamics of the system should be better with the stiffer bars.

Will report in on it....

 

[uHu]

Using the Toyota Handheld tester, the front suspension should be 6.9 MPa with a tolerance of 0.5 (996 +- 71 PSI) without the extra weight of the bumper/winch. So, with the extra weight, the pressure should read higher but how much higher?... you're in unexplored territory. If you go this route, please let us know your findings. I'm curious if you set it to 996 psi, how the ride would be and if you would retain all the height settings.

Just to clarify: With the extra weight, the TBs should be adjusted to give the same pressure as stock on the gas/hydraulic. That way the AHC can do it's job optimally.

It is better with higher rate TBs for the higher load, as long as the increase in rate is propotional to the increase in load, more or less. Otherwise the ratio between the gas (AHC) and steel (TB) springs would be out of balance.

Of course, the balance will be disturbed if you increase the load (weight) too much with the stock TBs as well. Don't know what is "too much" though. Could we have some guidelines on this maybe? From the experienced professionals? (i.e. at which weight increase to change to stock non-AHC TBs, (or stock diesel TBs for the gas LCs), and when to go for the HD TBs, etc).

U