i meant to lay the 2x4 between the jounce and the pad. but i do not have air suspension to see if all you need is a 2" block there.
i can see using the OEM jig to calibrate. but ideally you would need new jounces or at least verify new bumper length to yours to get back to tolerances in the suspension travel before it hits the pad. as not to tear a bag if too short.

 

Also, guessing those rubber jounce bumpers deform with weight on them. So you would with your method have to backwards calculate the thickness of wood and shave it to that thickness. Doable, Compress the jounce and measure it. Subtract that measurement from the 5+3/16” required gap. That is your required thickness of wood.

 

i do not think it is 5-3/16 from the tip to the plate.

 

What I said, stated another way: 5+3/16" is the overall gap required between flange of jounce bumper cup and axle.
So subtract the compressed size of the bump stop from this, and you have the required wood thickness. It HAS TO BE the compressed size of the jounce bumper (bump stop), not the relaxed size of it.

 

When I did mine I just used "before" or known measurements of how high the rear wheel arches should be from the ground and then just used a pair of jacks on the frame to hold it at the correct height and ran the calibration. Easy...

 

Interesting. But how did you know the proper height of the rear wheel arches from the ground? And how did you account for tire wear?

 

I did measure beforehand. Did not try to account for tire wear as the air springs have quite a bit of travel (can raise 2 inches of course with the button) so a small variance from stock height will not make much difference. The key for me was to get it back sitting level and the sensors back into the working range. Of course if you have a Tech2 you can always just watch the values and use a jack to see where it ends up in the valid voltage range of where it will allow the calibration to be set which is between 2.06V and 2.88V.

 

Tire wear? Learn how to properly measure ride height and compare the measurement to D-Height(5-3/16"/5.2"). Save that measurement and you're done!

 

When I replaced my bags and sensors several years ago I did just place a short piece of 2X4 between the axle and jounce bumper on both sides and then aired down. It did calibrate with no issue and I made note of the nice even height at 41.25 inches measured from ground to the wheel trim lip at center of the wheel arch. I was very happy with that stance.

Ive been perplexed with people saying they just jacked the truck to the desired height and did the calibration. I tried that and got "out of range" error. That makes sense as Im sure GM didnt want these sitting too high and unstable on the road.

I found this thread searching for "jounce". I just replaced the frame on my 2003 which had air ride with a donor frame from a 2006 which had coil springs. I put all my air ride on the donor frame. Backstory is that my frame rusted out with only 48k mikes on it. Body is still perfect. I think self inflicted rust by coating the frame with bad products which allowed corrosion behind the coating. Im in coastal Maine where we drive in salt water half the year.

Anyway, it appears that the jounce pumpers are different for air ride vs coil suspension trucks. Just my luck the coil bumpers (15057984) are still available new, but the air-ride bumpers (15062871) are not. Wish I had realized this before I dumped the old frame! Does anyone know the spec difference between the two jounce pumpers? And even better, does anyone have any nice condition air ride pumpers?!

Thanks!

 

ejsmall great info and if that P/No is correct they are indeed rare.

Sooner or later others are going to need replacing, so it would be good to get a solution.

Fairly confident I measured mine and made a very approximate model below, this may at least help in determining a suitable replacement. Without removing it I can't add much more detail such as bolt hole size etc.



May be other GM trucks use similar one that might fit, example this eBay link but it's probably going to take some measuring-up

Hope this helps in some way.