Adjusting torsion bar to level front side to side, with AHC (1 Viewer)

[2001LC]

I'd like to start by measuring height according to 2001 Land Cruiser FSM:
Front: A - B 71mm
Rear: C - D 51mm
Are these FSM measurements the same for 00 & 01 LX470 with AHC?

Notes: I'm adjusting the torsion bar to level the front, and hope the rear is leveled at same time, in my 01 LX470 with AHC.

I've got ground to fender-well a 5/8" height difference from DS to PS, with DS being lowest as is generally seen. The rear DS is 1 5/8" higher then front DS, and the rear PS is 1 1/4" higher than front PS. This is with ~15 gallons of gas in the tank.

I just flushed AHC, but have no way of measuring to see if I have neutral pressure in AHC system.

 

[ChuckB]

Definitive list of AHC maintenance items Try this link. Lots of info.

 

[LBridges]

I'd like to start by measuring height according to 2001 Land Cruiser FSM:
Front: A - B 71mm
Rear: C - D 51mm
Are these FSM measurements the same for 00 & 01 LX470 with AHC?

....

From 2000 LX FSM

Front - A-B: 82.7mm (3.256 in.)
Rear - C-D: 71.2mm (2.803 in.)

 

[PADDO]

From 2000 LX FSM

Front - A-B: 82.7mm (3.256 in.)
Rear - C-D: 71.2mm (2.803 in.)

@2001LC these measurements correlate very closely to the 19.75 and 20.5 inches axle center to fender bottoms often mentioned. Note that these height measurement are influenced by your TBs but are ultimately set by the height sensors. Three steps here: (1) get FR to FL level (2) adjust overall heights with the height sensors as necessary and (3) adjust torsion bars for optimum front neutral pressure at N height. Rear pressure, assuming it's high, is managed by new coils and I'll advocate adding 30mm spacers at the same time for a better outcome. Without a method of reading your pressures you've got very little to no chance of getting it dialed in for optimum damping and full load carrying capacity.

 

[PADDO]

I just flushed AHC, but have no way of measuring to see if I have neutral pressure in AHC system.

If you have hydraulics you have neutral pressures - they may be high, low or satisfactory. The term "neutral pressures" refers to the hydraulic pressures in the front and rear circuits that's necessary to lift and maintain the vehicle at its preset Normal height. If measured physically at each damper these pressures will be lower (1.2MPa) than the pressures reported into the ECU from the pump output pressure transducer and displayed via Techstream.

 

[2001LC]

Definitive list of AHC maintenance items Try this link. Lots of info.

Thanks I've been reading, only to page 2 of 18.

From 2000 LX FSM

Front - A-B: 82.7mm (3.256 in.)
Rear - C-D: 71.2mm (2.803 in.)

This and the PM is just what I needed, thanks again.

@2001LC these measurements correlate very closely to the 19.75 and 20.5 inches axle center to fender bottoms often mentioned. Note that these height measurement are influenced by your TBs but are ultimately set by the height sensors. Three steps here: (1) get FR to FL level (2) adjust overall heights with the height sensors as necessary and (3) adjust torsion bars for optimum front neutral pressure at N height. Rear pressure, assuming it's high, is managed by new coils and I'll advocate adding 30mm spacers at the same time for a better outcome. Without a method of reading your pressures you've got very little to no chance of getting it dialed in for optimum damping and full load carrying capacity.

I used ground up to measure as it's easier to eye ball, I'll switch or convert to axle to fender measurement to get in the ball park. Currently I'd estimate I'm .625" low in front & .75 low in rear based on the 19.75 & 20.5. Are the 19.75 front & 20.5 rear good numbers to use which would be a rake of ~3/4"?

Using the info LBridges gave me and FSM height measurement procedure, I'm way to low in front. Visually from rear it looks as if DS rear is low here's what I got last night: A - B front PS 1 1/4" DS & 1 1/8 PS, C - D 2 7/8 PS & DS.

I'll need to fill the gas tank or at least weight the tank side to compensate (not the PS as I did last night) and take all measurements again. Then I'll adjust Torsion bar to get L&R equal height. Should I also tighten torsion bar (raising front) on each side a bit to reduce rake?

I'll be stop from further testing and adjusting after that for lack of tool to read pressure, unless there is a workaround?

BTW I've got 285/50R20 on currently, would this tires size change the measurement?

If you have hydraulics you have neutral pressures - they may be high, low or satisfactory. The term "neutral pressures" refers to the hydraulic pressures in the front and rear circuits that's necessary to lift and maintain the vehicle at its preset Normal height. If measured physically at each damper these pressures will be lower (1.2MPa) than the pressures reported into the ECU from the pump output pressure transducer and displayed via Techstream.

Thanks for clearing that up.

 

[PADDO]

Re your front measurements: pop the hub dress cap off and put dots with a marker pen in the centers of the grease caps and measure to the fender bottoms. At the rear you can pop the dress cap off and stick a pencil, tapered punch or similar in the axle dimple and use that as your reference.
What you're trying to achieve is very straight forward and if you go to the end of "the definitive list..." and read backwards a few pages you'll get the idea of what needs to be done and in what order. You'll need to stop thinking conventional suspension and start thinking AHC e.g cranking TBs doesn't change rake or adding coil spacers doesn't change rear height. It will all make sense

 

[2001LC]

Thanks @PADDO.

 

[White wings]

I love this site

 

[landdriver]

My measurements on axle to fender for both left and right are practically the same but my sensors say my left side is higher by almost 4mm. Which is more of a factor for the adjustment? sensors?or physcial measurement? how do i procoeed?

front pressure sensor at 6.7 rear pressure at 5.9. read by obdlink. half tank conditions. no armor. oem winch up front. 2003 land cruiser with ahc gcc spec. 65k KM on the clock.

 

[uHu]

My measurements on axle to fender for both left and right are practically the same but my sensors say my left side is higher by almost 4mm. Which is more of a factor for the adjustment? sensors?or physcial measurement? how do i procoeed?

front pressure sensor at 6.7 rear pressure at 5.9. read by obdlink. half tank conditions. no armor. oem winch up front. 2003 land cruiser with ahc gcc spec. 65k KM on the clock.

A bit late answer... When the truck is straight but the sensors give different readings, you adjust the sensors until they show approx the same, but 4 mm is within reasonable range. No need to do anything.
The front height is set according to the average of the two front sensors. If you wanted to adjust away a difference of 20 mm on a level truck, and your physical height is correct, you would adjust both sensors, one up and the other down, so that the average is still zero at the same physical height.

 

[landdriver]

A bit late answer... When the truck is straight but the sensors give different readings, you adjust the sensors until they show approx the same, but 4 mm is within reasonable range. No need to do anything.
The front height is set according to the average of the two front sensors. If you wanted to adjust away a difference of 20 mm on a level truck, and your physical height is correct, you would adjust both sensors, one up and the other down, so that the average is still zero at the same physical height.

Thank you for straightening that out for me. im trying to get everything up front up to spec so i can somehow figure out how to increase the damping up front. On the comfort 2 and sport 1 setting, the front end bounces a bit too much on uneven concrete roads. The rear end damping is good. just the front end.