Time/risk to adjusting torsion bars (1 Viewer)

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Ridgefield, WA
I have a LX470 that I picked up a couple months ago. I have noticed a decline in ride quality over the last few weeks and that the LX now has a stink bug stance. I thought that the LX was set to ride flat.

I'm taking a 3 hour road trip with the family this weekend and debating the wisdom of adjusting the torsion bars before I go.

Is it more or less fool proof or are there gotchas that could disable the cruiser for the weekend?

How long should I expect to spend?

From what I've read, adjusting the torsion bars is a pretty straight forward job. And i have ordered a tool to measure the pressure in the AHC system to set the front to spec, but I won't get it in time for this weekend.
 
The AHC will seek it's own level regardless of what you do with the bars. The correct procedure is to hookup a laptop with TechStream and adjust the torsion bars to yield the specified globe pressure. A copy of the FSM is downloadable (search for it). Not sure what tool you ordered, but you only need the cable and software. About $35 on eBay.

There are other methods to manipulate the system by messing with the AHC height sensors or by buying the Slee override module.

If you adjust the bars without measuring pressure the AHC will still seek the same ride position, it will just be over/under working the hydraulics. I've put 700 lbs of flooring in the back and upon engine start it comes right back up to normal.

A positive rake of about 1 to 1-1/2" is normal and what the vehicle wants to have. There was recently a debate on this, but if it were my rig I'd leave it with a positive rake. YMMV.

Edit:

For the OP, here are a couple of links on Torsion Bars and AHC. My 04 is a stock grocery getter so I've not messed with any type of lift or adjustment. From these links it sounds like it's pretty easy to manipulate the front sensors. But again, the correct use of torsion bars is to set pressure in the globes and then allow the system to manipulated height and ride.

One other thought: degraded ride quality is associated with dirty fluid. You may have some debris in there blocking the normal workings. If it's due for a flush this would be a good starting point. Lexus of Portland sells the fluid. It's surprisingly expensive.

https://forum.ih8mud.com/threads/wth-ahc-correcting-the-torsion-bar-lift.452833/#post-6287841

https://forum.ih8mud.com/threads/adjusting-torsion-bar-with-ahc-questions.677799/#post-8208718
 
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A positive rake of about 1 to 1-1/2" is normal and what the vehicle wants to have. There was recently a debate on this, but if it were my rig I'd leave it with a positive rake. YMMV.
My LX levels perfectly with 3-400 pounds of wood stove pellets in the rear, exactly what it's supposed to do.

I don't understand the issues about the rear being higher than the front.

Stev3
 
Please share what tool You ordered to measure your pressures?
 
Measuring each corner (hub center to fender bottom whilst parked on flat level ground engine running and at N height) will help us speculate. You should be looking at heights of approximately 19.75 inches front and 20.5 inches rear, or there abouts. Extreme stinkbug stance, bum WAY up, suggests a failed rear height sensor or loose bracket; or you could have a front height sensor that has slipped or is on the verge of failing. As has been correctly pointed out your torsion bars don't vary your height - they just adjust cross level and front neutral pressure (the system's internal pump output pressure to lift the vehicle from L to N).

Now degraded ride quality could be due to any one or combination of: failed globe(s) - do the fluid reservoir graduation counting test; vehicle overall too high at N (gives high neutral pressures); slack rear coils (high rear neutral pressure) and the most common cause is torsion bars out of adjustment (too slack causes high front neutral pressure). Old and degraded fluid is not at all conducive to good ride quality and system longevity either. With the correct tool, Techstream, and a 30mm socket adjusting your front neutral pressure is less than one banana. With some height measurements we can hone in on your issue.
 
She's about an inch or so lower in the front.
Exactly. Unloaded should have a positive rake at the factory settings.

I've not measured mine heavily loaded but I would have thought AHS would have put her back to the exact same spot, assuming within acceptable pressures.
 
Thanks for the comments and links so far.

More information about my rig and symptoms:
2000 LX, 149k, grocery getter, so far.

Every now and then there is a noticeable correction from in the AHC, at least I assume it is a correction, but maybe addtional pathology. Happens when stopped, such as stop light the nose will dip down suddenly and then come back up. I kind of doubt this is normal, but I haven't seen anything on it yet. The degraded ride quality is I can really feel the bumps now. I usually drive in Sport. It's almost like riding in an overdamped 60. Comfort is too soft for my taste, but I drove around in comfort a bit today. It damps out the bumps better, but the oscillations when going over a bump take longer to damp out. It's a little like being in small boat on big water.

Here are my measurements from the center of hub to wheel well, flat surface, N position, engine on:
DF: 18.625 PF: 18.875
DR: 20.625 PR: 20.75

It looks like I've got an extra 0.5" to 1" of rake going on and a low front position by about an inch.

The fluid was flushed and replaced about 9 mo ago by the PO, during what appears to be a regular service visit. It wasn't a Toyota or Lexus dealer. The line just describes it as AHC fluid, seems reasonable he got the right stuff. The last time I was down in the 'Tron, I picked up a 3L tin of AHC fluid from Kuni for a cool $45, thinking I might bleed the system, if not do a flush. (I still need to find the FSM -- no idea how many litres the system takes.)

It looks like I didn't finalize my order for the Techstream cable and software from Amazon last night, but that is the tool I plan to use to get a reading on the pressure.

From what I have read so far on Mud, I was guessing I had tired torsion bars and cranking them up a bit would help relieve some of the load on the AHC pump. Reading the "WTH" post, it sounds like the pump should overcome the spring fatigue, and maybe the front sensors need to come up or an issue with the hydraulics themselves. That said, the car's stance looks different to me, which makes me think it isn't the sensor, but maybe it's my imagination.

I probably have 2 hours tomorrow I can monkey around with this before we leave. Is it worth messing with before getting on the road or should I wait until I have the Techstream to monitor pressures?
 
You'll need 2 cans for bleeding the accumulator and the 4 globes...you'll have some left over.

I wouldn't start something before a trip if I thought it might take up to 2 hours...Murphy's Law seems to operate well when you're in a hurry and up against a deadline.

Good luck if you do decide to go for it.

Steve
 
I'd go for it, very likely your front neutral pressure is high, bet the rear is too but you won't know till you can hook up TechStream. I'd put 2 or 3 turns cw on both TB adjuster bolts and see if that improves things. It won't kill the system.
 
If you do any adjusting to the torsion bars, just be sure to get the front aligned before your trip!!
Or you'll be needing tires soon.
 
If you do any adjusting to the torsion bars, just be sure to get the front aligned before your trip!!
Or you'll be needing tires soon.
LC without AHC yes, LX with AHC no. AHC height is set by the height sensor feedback loop to the hydraulics, not the torsion bar loading. In AHC vehicles the torsion bars do two things; adjust cross level and adjust front neutral pressures.
 
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^ Thanks for the clarification Paddo!
I'm from the other side of the tracks and can't afford one of those high-falutin fancy LX's so i wouldn't know.:hillbilly:
 
Well, instead of having a little time to crawl under the rig to add a few turns worth of torque to the tb, I got suck into working a bit. Probably just as well.

I have the obd2 tool coming in the mail. Should be here about the time I have another window to play at being a mechanic. This will let me make the adjustment a little more informed, if not methodically.
 
Well, I got the techstream ODB2 reader and software via amazon. Then I lost about 10 hours over the last week trying to convince it to play nice with my computer. I tried every hack I could find and have done everything but format or setup a virtual machine. Sick of that fight, I decided to crank up the tb adjustment bolts today, 3 turns.

So far so good : somewhat improved ride. Hub to fender measurements are better by 1/2" all around, higher in front and lower in back.

I will get a pressure reading Monday or Tuesday with a buddy's reader.

While under the truck, I noticed my adjustment bolts don't have the same kind of offset measurement shown in the FSM. this spec shows the bolt head the be several mm subflysh. Mine are several proud from the framework. Turning the bolt helped a bit. Pic show before 3 turns CW. Should I be worried about this?

1422752151675.jpg


1422752186064.jpg
 
I believe i bought the same software as you. I made sure I used XP. After getting the TS software installed, I also had to install the sn PATCH (separate program) and then install the ODB driver (separate program), I did this while the ODB was plugged into the USB port on the computer and watched its led turn from Red to Green. Then after it recognized the car I had to make it acknowledge it was an LX so it would see the AHC.

Did you install all three programs (all located on the disc) ?
 
Yeah. I got as far as getting the driver's to work, green light on ODB2 read head. I'm pretty sure the issue is Win7. A virtual machine running XP, might be the trick i need.
 
What kind of OBDII dongle do you have? Can you get an app for it? The type I have uses the Torque app (Android) on my phone and it really was "plug-n-play".
 
Well, I got the techstream ODB2 reader and software via amazon. Then I lost about 10 hours over the last week trying to convince it to play nice with my computer. I tried every hack I could find and have done everything but format or setup a virtual machine. Sick of that fight, I decided to crank up the tb adjustment bolts today, 3 turns.

So far so good : somewhat improved ride. Hub to fender measurements are better by 1/2" all around, higher in front and lower in back.

I will get a pressure reading Monday or Tuesday with a buddy's reader.

While under the truck, I noticed my adjustment bolts don't have the same kind of offset measurement shown in the FSM. this spec shows the bolt head the be several mm subflysh. Mine are several proud from the framework. Turning the bolt helped a bit. Pic show before 3 turns CW. Should I be worried about this?
You're thinking about this too much. There was another member who tried adjusting his TB to that image and screwed his system up by under loading the hydraulics (too much TB spring). Honestly, all you have to do is adjust the TBs as per the numerous AHC specific FSM procedures previously posted. If you follow that image in your post from some random FSM page you will chronically under load your AHC and it won't work as designed. Also, the height sensors set the height, did you measure height after adjusting TBs and starting the vehicle so it could relevel? I'm not sure how you can get a 1/2 inch height increase without adjusting the sensors.
 

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