H2-G fully endorse what has MixManSC says.

Attached a little info on ride-height calibration which may help.

For a laugh, google "ch-47816 tool" and see the prices, I swear I should get some made and sell them.

Without blocks, I set my trim point so the gap between the "top of the wheel" and the "lower edge of the plastic fender" is the same all round, both front and back. It also just happens to be roughly 1/2 way on the ride-height sensor voltage.. It may not be perfect but it looks close.

Yours may be different with the lift kit etc

 

That would buy a lot of tape measures!

CH-47816 Calibration Blocks are 5-3/16" long, measure from the metal flange at the top of the bump stop to where the bump stop contacts the diff housing. Set it at this height by lifting on the bumper hitch and calibrate from there.

 

love it, here in the UK to use a measure 📏 you'll need to go on training course 1st 📚 📝

 

YT has a 4min course.

 

Thanks oceanbrave for the air suspension calibration procedures. I'll get my hands on a Tech 2 and follow the steps although with the Fabtech lift kit on my H2 I'm not sure of the outcome. Given the cost of calibration blocks I sure hope they are made of gold.

After reading all of this information and watching the posted/linked videos I'm beginning to think open heart surgery would be an easier procedure.
I think I'm going take oceanbrave's advice and take a "wait and see" approach before I start replacing air lines/bags and messing with the AS unit. I could wind up spending a lot of time and money, and in the end if it's just a slow leak I can live with that.

 

Calibration is not as hard as it seems. The Tech2 will give you valuable access to the sensor voltages as well. Basically at "normal" ride height they should be reporting around 2.4v to the AS module but that can vary some which is why they need to get calibrated.

Essentially it will go like this. (doors MUST be closed, ignition in, engine NOT running when doing the Tech2 AS module functions)
Determine what your "normal" ride height should be measuring from the ground to some common point like the center of the rear fender opening.
Jack / block the body in some manner to get it dead level to the same measurement on both sides.
Connect Tech2 - go the the AS module.
Use the Depressurize System function which will deflate the air springs letting it sit on the jacks. The body should be sitting firmly and level on both sides on your jacks or whatever you use to hold it level at the correct "normal" height you measured.
Then do the Calibrate Trim Height function. That will calibrate the sensor values to the height you have it sitting at.
Then do Pressurize System - when you do this part watch the air springs carefully to make sure they seat over the lower centering points on the axle. Wait until it lifts the rear off of the jacks. Stop it and disconnect.
Crank it up, doors closed and it will settle to its newly calibrated position.

Really is a fairly simple process.

 

Thanks again MixMan for your input and simplifying the process for me.