Zr2 front suspension

PBNB · January 24

On 1/22/2026 at 6:18 PM, OS RR said:

You can see "Leveled" next to an AT4X. What I can't figure out is why the front wheels are sucked in more (in relation to the rear) on the leveled truck while sitting practically at the same height as the AT4X. Is the something inherently different with the ZR2/AT4x suspension parts that causes this difference?

Price wise, a decent leveling kit and the ZR2 kit work out similarly. AEV has figured out how to fit 37x13.50 (w/ 18+ offset wheels) on these trucks with some minor trimming and fender liner brackets.

I just went through this and I think the control arms are going to make a difference and I suspect that the AT4X has longer upper and lower arms. When you lift the other trucks to level say ~2" the arms are rotating inwards pulling the wheels inward. If you are looking for the same amount of wheel poke you could also go to a different offset that would move the wheel center outward. So if you lose 3/4" of poke by lifting it, you could get a wheel with 3/4" more offset to even it out.

Keep in mind that moving the wheel outward will have more affect on tire rubbing when you turn the wheels.

If a 4" life is done, it will come with different control arms to move the wheels outward as well as a bunch of other bits to change the angles of the ie rods and pitman arm, etc...

OS RR · January 24

I don't see how the control arms could be much longer (except the uppers by just a hair to account for ball joint angle and camber). Cognito is quoted on their site saying the ZR2 uppers are .2 inches longer. The CV axles would need to be longer if the knuckles were pushed out.

And don't think most 4" kits need anything more than knuckles and bottom drop crossmembers. The knuckles are taller with the tie rod mount point moved compared to stock to keep them flat.

https://cognitomotorsports.com/cognito-super-stock-kit-for-2024-gm-2500hd-at4x-zr2.html

Just my opinion, I feel like that kit is waste of money outside the steering brace parts.

Edited January 24 by OS RR

PBNB · January 25

I had a look at the kit, and you are probably right about its usefulness. When I put my Cognito UCA's in my truck, I didn't notice too much extension over the ones I took out. They are beefy and the comment from the alignment shop was that the alignment settings were very close to being correct (I just had the truck aligned 6 months) before levelling it. I need to check to see how much the front wheels are sucked in but haven't used it very much so it has been sitting. I haven't noticed any rubbing of the tires but I am only running 295/70R18's so not as big as most.

I was really only going for a modest change but I wanted the shocks to work so set my target at 1.75" in the front and it seems very tall now that I have it done. I also used the SuspensionMaxx diff lowering spacers to deal with the added angles of the CV joints.

I know there have been some threads that talk about swapping out the regular suspension parts with AT4X parts using all OE parts and there are probably part numbers in this thread but I didn't go back to read all the comments. I guess that would be the best way to go to get everything properly setup.

Are you looking at lifting an AT4X to 4" or lifting a non-AT4X truck or something else?

UTGOZER · February 11

This is about to go down, or maybe I should say UP!! Huge thank you to all that have added to this thread. Any tips, tricks or words of encouragement appreciated.

UTGOZER · February 11

On 8/22/2025 at 6:25 PM, Epsilon Plus said:

I just got my HTOs in and I'm ready to put them on.

What are your thoughts on the Fox 2.5 HTO's over the Bilstein 5100's you had previously?

GMCnewbie · February 11

4 hours ago, UTGOZER said:

Any tips, tricks or words of encouragement appreciated.

The most difficult part I had replacing was the differential carrier bracket. More specifically, the driver's side bracket. I did one side at a time and didn't realize there was no way to easily remove or install the driver's side bracket with the passenger side fully installed. Pro tip: loosen the nuts on the passenger side bracket as much as you can without removing them completely. Also remove the skid plate. That will allow everything to droop about an inch or so making it super easy to remove the driver's bracket and install the new one.

Outside of that, the rest was fairly straight forward from what I recall.

OS RR · February 17

Can a mod pin this thread? And the other one?

UTGOZER · February 26

Getting through it!!

GMCnewbie · February 26

Looking good. Let me know how well those Bilstein shocks ride after you complete the full swap. I went with the Fox 2.5 HTO's. I like the ride quality overall but I sometimes feel like a little stiffer ride might be nice. Granted, I also replaced the torsion bars and leafs with the Comfort Ride setup from Cognito. So that may leave my setup a little looser than others. But my ride quality is light years better than stock. So no complaints

Chuck FB · February 26

The cv axle nut, what deep metric socket size was that ? ( 36 mm used to be the common size for cv's but I gather now other sizes are being used as well )

Also did you run into any unique sized hardware as it seems all too often socket or wrench sets unless high end brands, almost always are missing certain sizes or the sizing doesn't go up large enough.

UTGOZER · February 26

Overall not too bad.

I broke a wheel speed sensor getting it out of the Knuckle. $21+/- so not too bad.

Thanks to @Epsilon Plus I didn't put the dust shield on backwards but I did put the o-ring on the wrong side so I had to go back and fix that.

I'd say to anyone doing this swap in the future, pay close attention to the bolt orientation on the upper control arms — including the color. Yes, the color. One bolt has a light blue coating, and the other is natural (almost white). They can be installed backwards/upside down, so make sure each one goes back in its original position.

Also, my 22' GMC does not have the holes pre drilled in the crossmember for the ZR2/AT4X transfer case skid. I will drill some and use thread taping bolts.

Alignment is in the morning!!

UTGOZER · February 26

Yep, 36mm

That and the Torsion Bar Unloader were the only tools I had to buy.

Tools listed earler in this thread were all that was needed.

UTGOZER · February 26

25 minutes ago, GMCnewbie said:

Looking good. Let me know how well those Bilstein shocks ride after you complete the full swap. I went with the Fox 2.5 HTO's. I like the ride quality overall but I sometimes feel like a little stiffer ride might be nice. Granted, I also replaced the torsion bars and leafs with the Comfort Ride setup from Cognito. So that may leave my setup a little looser than others. But my ride quality is light years better than stock. So no complaints

I will be sure to report back!! I was eyeballing the Fox 2.5 HTO's but have always been pleased Bilstein's and the $350 total cost helped.

UTGOZER · February 27

Boom! Done!!

It turned out just as I hoped.

Again, thank you to all that have contributed to this thread.

KvetL5P · February 27

6 minutes ago, UTGOZER said:

Boom! Done!!

It turned out just as I hoped.

Again, thank you to all that have contributed to this thread.

Looks great! Overall how hard would you say this was and how long did it take start to finish? Also just curious what size jack and jack stands did you use?