Zr2 front suspension

KvetL5P · April 7, 2025

8 minutes ago, Chuck FB said:

And as you measured the stock bars to the cognito and stands to reason they are somewhat softer and would loose some height due to them, how much is hard to say but it would be some. One thing you could do if there are any AT4X around assuming their fender trim is the same as all the other GM trucks so your measuring apples to apples, is to measure the best you can from the underside of the fender trim straight down to the center of the hub. That takes away all tire height and tire inflation variables. Do the same right now with your truck before you do anything more ( make sure the truck was driven to the flat area you park it on and not jacked up and then set back down ) and measure it the same way so you have that fender to center of hub referrence as a guide. Then when you swap wheels etc, its always that same hub to fender spec when parked on a flat surface to do your fine adjustments to get the truck side to side height like you want as well as total suspension lift.

On my truck I bought recently I discovered that the left side was a 1/2 inch higher than the right side and yes the fuel tank was full and not really anything else in the truck. That really showed up on the key bolts as the right hand bolt was sticking out quite a bit more, GM seems to do a rather poor adjustment at the factory for the ride height I have found, the trucks are not consistent off the assembly line.

On my 22 3500 I had the same issue front passenger side was at least half an inch lower. I've got my keys cranked (3 turns) now, I saw my first AT4X AEV in the wild the other day and parked beside it. It's an absolute beast! Even with my keys cranked it was towering over my truck.

Chuck FB · April 7, 2025

33 minutes ago, KvetL5P said:

On my 22 3500 I had the same issue front passenger side was at least half an inch lower. I've got my keys cranked (3 turns) now, I saw my first AT4X AEV in the wild the other day and parked beside it. It's an absolute beast! Even with my keys cranked it was towering over my truck.

I had made a comment about my findings on my truck and Newdude had commented that he felt they did that because of the fuel tank as well as a driver behind the wheel to offset that uneven weight. Yes I can see that being valid to a point but also its not like these are light trucks with wimpy suspension that struggles to carry a bit of weight. I plan to keep an eye on the suspension and if I see an issue with it leaning left then I can adjust a little if needed. Driving on crowned roads that lean the truck to the right and the truck already leaning to the right, just doesn't make a lot of sense in my mind and couldn't help myself but adjust it. At this point I turned the right key up 4 1/2 turns and that caused the left side to go up some as well so I backed the left side off by 1/2 a turn. Be it right or wrong the end result was lifting the left side a 1/4 inch and the right side 3/4 of an inch. Now what is official "factory height" that is a good question !. Do you know what your hub center to underside of the fender molding distance is, mine is now set to 25" where as the factory "average" between the two sides was 24 1/2"

On that note, I have yet to bring it in for an alignment as that probably is the prudent thing to do so that I don't create any tire wear issues but the truck steers perfectly down the road so no complaints there. Did you have the alignment checked after your adjustments ?

I am surprised that an AT4X stands out that much relative to a stock truck, I haven't really thought of going to the dealer that did have one in stock ... then again I forgot that I was standing by one that was in the shop of a company that does detailing work and PPF and ceramic coating etc. There was no truck beside it to compare but it never jumped out at me as being so high that it seemed shocking. I guess after being around all the lifted trucks up here in parking lots and ripping down the road that are HIGH with big lifts and some with fairly large tires of all three brands, anything stock doesn't stand out very much.

Edited April 7, 2025 by Chuck FB

KvetL5P · April 7, 2025

5 minutes ago, Chuck FB said:

I had made a comment about my findings on my truck and Newdude had commented that he felt they did that because of the fuel tank as well as a driver behind the wheel to offset that uneven weight. Yes I can see that being valid to a point but also its not like these are light trucks with wimpy suspension that struggles to carry a bit of weight. I plan to keep an eye on the suspension and if I see an issue with it leaning left then I can adjust a little if needed. Driving on crowned roads that lean the truck to the right and the truck already leaning to the right, just doesn't make a lot of sense in my mind and couldn't help myself but adjust it. At this point I turned the right key up 4 1/2 turns and that caused the left side to go up some as well so I backed the left side off by 1/2 a turn. Be it right or wrong the end result was lifting the left side a 1/4 inch and the right side 3/4 of an inch. Now what is official "factory height" that is a good question !. Do you know what your hub center to underside of the fender molding distance is, mine is now set to 25" where as the factory "average" between the two sides was 24 1/2"

On that note, I have yet to bring it in for an alignment as that probably is the prudent thing to do so that I don't create any tire wear issues but the truck steers perfectly down the road so no complaints there. Did you have the alignment checked after your adjustments ?

I haven't had an alignment, however nothing seems to have changed, truck still drives perfectly straight. As for height, from what I recall i.measured from the ground to the fender edge. All 4 corners are at 41" or 41½.

Chuck FB · April 7, 2025

21 minutes ago, KvetL5P said:

I haven't had an alignment, however nothing seems to have changed, truck still drives perfectly straight. As for height, from what I recall i.measured from the ground to the fender edge. All 4 corners are at 41" or 41½.

I have the factory 275/65R20 tires although I believe I had dropped the tire pressures at that point so that would make a bit of a difference to the floor to fender measurement. I had made some notes and looks like I would be at around 41 on the front and 41 3/8 on the rear axle after my adjustments.

My steering wheel is slightly to the left though and this was from new, it never changed after I touched the keys. That I want corrected and have it all numbers checked at the same time just to be sure.

kylant · April 7, 2025

a few thoughts:

i am pretty sure the zr2/x is 1.5" lifted plus the height of the tire, 2.5" total.

the cognito torsion bars are softer. i have read over the years, they need to be cranked more to obtain the same ride height.

on both my 2020 and 2022, each full turn of the torsion bar adjuster bolt equaled 1/4" of ride height adjustment

trying to get all my ducks in a row.

i think i am going to go with all the 2/x components except for a kryptonite ucas, cognito torsion bars and keys, cognito soft ride mini-pack, and fox hto shocks. then i'll go with a method wheel and a 35" tire

KvetL5P · April 7, 2025

14 minutes ago, kylant said:

a few thoughts:

i am pretty sure the zr2/x is 1.5" lifted plus the height of the tire, 2.5" total.

on both my 2020 and 2022, each full turn of the torsion bar adjuster bolt equaled 1/4" of ride height adjustment

Thats was I figured as well. (3 full turns = 3/4" and not quite sitting lvl) My hope is to do the zr2 swap but run a 37x12.5 on the stock 18" (black wheel) which from what I've read is quite doable. Which gives me over 2.5" of total lift.

Chuck FB · April 7, 2025

21 minutes ago, kylant said:

a few thoughts:

i am pretty sure the zr2/x is 1.5" lifted plus the height of the tire, 2.5" total.

the cognito torsion bars are softer. i have read over the years, they need to be cranked more to obtain the same ride height.

on both my 2020 and 2022, each full turn of the torsion bar adjuster bolt equaled 1/4" of ride height adjustment

trying to get all my ducks in a row.

i think i am going to go with all the 2/x components except for a kryptonite ucas, cognito torsion bars and keys, cognito soft ride mini-pack, and fox hto shocks. then i'll go with a method wheel and a 35" tire

I guess I had forgotten that you were involved with this topic thread to figure out what you might do for a lift. From the sounds of it with a system like that, the new knuckle and not running the cv's or the tie rods at insane angles should in theory give the components the best life as well as the ride rather than the initial cheap method of cranking torsion bars and standing the control arms on end, and in the long run costing a crap load in premature worn out ball joints, tie rods, cv shafts, and a crap ride with no suspension droop so the suspension tops out all the time.

With this truck I have no desire to lift it but I also don't want it sagging down and bottoming out because the keys were set wonky. Also the curiosity about the cognito torsion bars as a method of softening the ride if I wanted to try that out in the future.

The irony is that I could have bought a ZR2 for less than I did this 3500 HC but a lifted truck beyond the height of the standard HD just wasn't a priority like it would have been years back, instead I wanted the 3500 capacity etc.

kylant · April 19, 2025

GMCnewbie,

any updates/pics?

i am starting to gather my parts. I have ordered Cognito soft-ride torsion bars, keys, and soft-ride mini packs, GM diff drop brackets. still debating on the rest of the front suspension. I will be going with the FOX HTO shocks. I debated between those and the the FOX elites, but I really can't justify double the cost of them

GMCnewbie · April 19, 2025

27 minutes ago, kylant said:

GMCnewbie,

any updates/pics?

Sorry. I've been traveling a lot for work. Sadly, the rear leaf spacers didn't get delivered until two days ago while I was out of town. I plan to swap the rear setup on Monday when I get home. I believe the new wheels/tires will be delivered on Tuesday. I'll take pics on Wed or Thursday when everything is completed. I did go back to the stock torsion keys because the Cognito keys lifted the front end more than I was expecting. Ill take a look at the total setup this week when all is installed and determine if I need to swap to the Cognito keys. I'll post updates.

kylant · April 27, 2025

gathering the rest of the parts to do this swap. I can't find lower control arm rear bolts. are they the same as the front?
do I need a total of 4 new bolts?

revrnd · April 28, 2025

On 4/18/2024 at 10:08 PM, Epsilon Plus said:

The ZR2 transfer case skid vs the baby Z71 skid. In the process of drilling the rear holes. Going to use through+bolts and nuts. Initially was going to tap M10x1.5 threads for one of the unused front Z71 bolts and add another, but didn't have the right 8.5mm or whatever PITA metric bit.

Fits on the 20-23 great, just need to drill rear holes.

M10 x 1.5 tap drill is 8.5 mm or a letter Q drill = .332" The closest fractional drill is 21/64" (.328")

Edited April 28, 2025 by revrnd

Epsilon Plus · April 29, 2025

I just punched through and used nuts.

In other news, a coworker parked a brand new 2025 diesel High Country 2500 directly next to me and I got out my tape and made a bunch of measurements.

My L8T truck on 37s is 3.5" higher in the front and 3" higher in the rear. I have my keys set at a reasonably close factory ZR2 level, not cranked and still maintain a factory rake (higher in the rear). Measurements were at actual body points like bottom of the mirrors, bottom of the rear bumpers....etc not just the fender flare height.

Edited April 29, 2025 by Epsilon Plus

kylant · April 29, 2025

what is the rake on your truck?

how much gap is there between the UCA and service perch? stock is about 2".

factory atx4 rake is 1 3/4", my at4 is 1 1/4"

i measured an at4x at the dealer. it only has 1 3/8" lift compared to my truck

also, do i need 4 new lower control arm bolts??

thanks

Edited April 29, 2025 by kylant

GMCnewbie · April 29, 2025

2 hours ago, kylant said:

do i need 4 new lower control arm bolts??

Yes, these bolts are one-time use bolts per GM. I've heard of some reusing their bolts. I replaced out of an abundance of caution. If you do replace, I strongly recommend purchasing online for a discount. The stealerships in Houston all marked them up to extreme levels. I want to say, one of the dealers wanted something close to $28 per bolt.

kylant · April 29, 2025

thanks. i ordered 4

I have everything ordered except for upper control arms. i am debating between stock x/2 or cognito.

with the stock arms, can the t-bars be turned up slightly (1/2") and still keep adequate droop? i know in stock position, there is about 2" between the arm and service perch (i measured on a dealer truck).

i like the cognito arms, but i really don't want to cut the service perch off the truck. I know this is done all the time, without issues. I have even done it on my buddy's truck.

thoughts?

Edited April 29, 2025 by kylant