Features:

• Adds 2-1/2" front and 1/2" rear lift
• Improves ride quality by adding front suspension droop travel
• Retains the OEM Multimatic DSSV shocks
• Includes billet front shock clevis bracket
• Allows for up to 37x12.50 tire on max 10" wide wheel with 0mm to +19mm offset
• OEM AEV Edition SALTA wheels do fit with up to 37x12.5 tire. Non AEV wheel fitment TBD.

The 2500HD AT4X/ZR2 model was first introduced in 2024. GM advertises that it includes a 1.5" suspension lift. Our comparison to the standard models disagrees with the front lift claim which indicates an actual 2.5"-3" of front lift compared to the standard models and agrees with the 1.5" for the rear. Rather than calling the front end a lift, we feel it is more appropriate to call it a leveling kit in the front plus an added 1.5" lift block in the rear. 

The front is more of a leveling kit because there is no added subframe and taller knuckle. The increased ride height comes via a different lower control arm that has a different torsion bar clocking to increase the lower arm angle at ride height, different bump stop position, .2" longer arm to get the track width back to spec due to the increased control arm angle at ride height. The upper control arm is also .2" longer, and the knuckle has a different shape in the neck but the important geometry is all the same in the knuckle as the standard models. 

Unfortunately, this increase in ride height introduces a couple problems. The AT4X/ZR2 has more front suspension up travel resulting from the increased ride height, but only 2-1/8" of droop travel in stock form which is a full 1" (35%) less than the standard models resulting in front shock 'top out' that is noticeable when traveling over dips and on the back side of large speed bumps. Also, GM has inherently created an accelerated wear issue with the pitman and idler arms with the increased ride height. Cognito has a patented solution for this in the Pitman and Idler Arm Support kit which is not included in this standard package but highly recommended to add-on.

This standard lift kit package adds a subframe, taller knuckle, and diff drops to create 2.5" of additional front ride height while increasing the front suspension droop travel to 3" which is the Cognito minimum standard for droop travel. The rear is lifted 1/2" via replacing the 1.5" block with a 2" block and longer u-bolts. The differential is also dropped to keep proper CV axle angles, and the torsion bars are kept up in the frame via the Non-Torsion Drop Bracket added to the lower control arms. The OEM Multimatic DSSV shocks are maintained in this standard package, by changing the lower clevis mount on the front shocks with a billet extended version. The rear shocks are maintained as is since rear lift only increases 1/2". For those looking for more suspension performance, opt for one of the other packages that include shocks and control arms to maximize the suspension travel and shock damping