WTH!!! AHC correcting the torsion bar lift ...

[lexi4darin]

Guys, what the heck is going on. Two things. First, my LX was leaning towards the drivers side pretty bad. I did the torsion bar adjustment to correct. The truck is now level between the drivers and passengers side.

Second, I have a forward rake of just over 1.5" right now. Isn't this lower in front than stock? I figured the torsion bars were week from the 10 years and 140k of use. So I used the torsion bars to raise the front about an 1". I figured it wouldn't be leveling the truck completely from front to rear (leaving a slight 1/2" - 3/4" forward rake) but would still be a nice compromise. However, once I drove the truck the AHC auto adjusted ride height back down so that I have the huge 1.5" rake.

So what's the proper way to correct the 1.5" forward rake? And what's happens to the suspension composition if the torsion bars are torqued up but the AHC is compromising in the other direction? Seems like something now out of alignment, got too much pressure, or something? ?

 

[jOnathN]

AHC is acting as per design. The AHC does not care about spring and torsion bar force, it cares about measured height. AHC takes input from three height sensors (two in front, one in back) and adjusts itself as necessary.

So...if you want to change the height of the vehicle, adjust the sensors. Changing the torsion bar setting will have no effect on vehicle height. It will however change how much load the AHC carries vs. the torsion bars.

The way to go about what you want is to first adjust the sensors until the truck height and rake is where you want it. Then go about adjusting the torsion bars to get the neutral pressure back into spec. Ditto at the rear except there is no way to adjust the spring tension without changing springs.

The front height sensors are an easy adjustment. You can see them in wheel wells near the top and behind the spring perches. There are pictures and instructions on mud somewhere. Try searching for "adjust ahc sensors" and the like.

 

[jOnathN]

RE: your last question...having the torsion bars torqued higher than spec will not harm anything. It will reduce the load on the AHC in front and probably prolong the life of the system. Might make the ride a little more firm though.

 

[sonk76]

AHC is acting as per design. The AHC does not care about spring and torsion bar force, it cares about measured height. AHC takes input from three height sensors (two in front, one in back) and adjusts itself as necessary.

So...if you want to change the height of the vehicle, adjust the sensors. Changing the torsion bar setting will have no effect on vehicle height. It will however change how much load the AHC carries vs. the torsion bars.

The way to go about what you want is to first adjust the sensors until the truck height and rake is where you want it. Then go about adjusting the torsion bars to get the neutral pressure back into spec. Ditto at the rear except there is no way to adjust the spring tension without changing springs.

The front height sensors are an easy adjustment. You can see them in wheel wells near the top and behind the spring perches. There are pictures and instructions on mud somewhere. Try searching for "adjust ahc sensors" and the like.

Agreed with everything above from my own experience. The one thing that I was never able to achieve was adjusting the lean by adjusting the front sensors. Even though there are two sensors in the front (one on each side), I was not able to adjust them independently in such a way as to correct for the lean... seems like the system is connected left and right (i.e., the same pressure on both sides.)

 

[lexi4darin]

Sonk76 - my lean was fixed and previously was severe. After a month of measurements on various terrain and many on my routine routes it was discovered my LX was nearly an inch to the left with lean. Spot on an inch when the ground promoted lean; just a tad over 1/2" when the ground reduced lean; just a tad over 3/4" when the ground was flat to the eye.

Honestly, I'm confident the torsion bar adjustment will fix your lean (if you're problem is related to front suspension). My LX is within 1/16" of an inch right (total luck as this accuracy was happenstance) and has stayed even for a full 48 hours.


To jonathan - thanks your break down gives me a better idea and the LX some hope. Sounds like I approached this job in bakcwards order (and a lil under prep'd).

 

[eleblanc]

Don't use the torsion bar to raise the truck. Torsion bar on AHC should be use to level the truck side to side and make sure that the pressure in the front shock are within FSM specs, otherwise the ride quality will be alterated and might be bad. You should use the height sensor to raise the front, not the torsion bar.

You should now use a pressure gauge to check if you are within specs or use the factory tester to read pressure data in the ECU.

You will not solve a lean with the height sensor, i've try that.

EDIT: Looks like jOnathN had already explained it.

 

[r3run33]

I agree with the above staement; if are using the torsion bars to adjust the level of the truck you are not fixing the problem. I have a similar problem but have not fixed yet (waiting for spring to remove entire ahc) My problem is that my drive way slopes down and away; so that if you park on it the right rear is lifted to put the truck level. Sometimes after starting and leaving the truck does not level out so the right rear is still higher. Last year all the sphere's where replaced under warrantly but the problem came back aprox 6 months later. After researching all the AHC problems I dont think there is a solution out there to premamently fix the problem meaning you will always have to update spheres or flush systme etc. and to me thats not acceptable. just my opinion

 

[sleeoffroad]

Guys, what the heck is going on. Two things. First, my LX was leaning towards the drivers side pretty bad. I did the torsion bar adjustment to correct. The truck is now level between the drivers and passengers side.

Second, I have a forward rake of just over 1.5" right now. Isn't this lower in front than stock? I figured the torsion bars were week from the 10 years and 140k of use. So I used the torsion bars to raise the front about an 1". I figured it wouldn't be leveling the truck completely from front to rear (leaving a slight 1/2" - 3/4" forward rake) but would still be a nice compromise. However, once I drove the truck the AHC auto adjusted ride height back down so that I have the huge 1.5" rake.

I posted this in your other thread. Did you not see that post? Also someone posted the link on how to adjust the height. Both in the other thread.

 

[lexi4darin]

Slee, thanks. I revisited the thread and between it and this one, I'm covered. I think I rushed into the job without having all my ducks in a row. Also, the last post in the other thread came up after I had already walked away from the computer for the day and start the job on the torsion bars. Anyway, no worries.

I'm buying 3 more cans of AHC for a top off and to save for future use. To fix the forward lean, I'll adjust the height sensors and then move the torsion bars down a bit cuz the ride is really jouncy right after all the adjustments.

The LX is riding holding level in terms of the leaning to the driver's side. Very flat still. Of course it's still raked.