GMCnewbie

That's smart. Didn't think to try breaking it up into separate orders.

I don't believe GM made any changes to the suspension for the '25 models, but you should absolutely verify all part numbers before purchasing anything. I ordered my parts in Oct when GM was offering 35% off all suspension parts. Not sure if they similar deals now. I looked for deals online and found prices to be similar to the 35% from GM, but the online sites charged a ton for shipping. I want to say i saved like $500 on shipping alone. Something to keep in mind as you navigate this upgrade.

I do have the parts in my garage (knuckles, control arms, etc). When I looked them up months ago, the parts for the '24 AT4X had the same part numbers as the ZR2 which makes sense as they're effectively the same trucks underneath the skin layer. Now you have me wanting to go back thru the part numbers to make sure I didn't grab a wrong part. lol

My understanding is the AT4 and AT4X share the same keys based on part numbers that I looked up a while ago. Granted, I have yet to do my conversion even though parts have been in my garage since Nov. Hoping to take a few days off next month to work on this project.

Have you swapped out your stock shocks? If so, which did you choose and how do you like them versus stock? I purchased the Fox 2.5 HTO shocks for mine, but haven't had time to install.

Just placed my parts order with GM. Saved a bunch on shipping by having the parts shipped to the stealership. Found several discount GM parts stores online that offered the parts a few dollars cheaper, but added $500 for shipping on the back end. In the end, my total price for all parts (UCA, LCA, knuckles, differential brackets, spacers, bolts, and nuts) was $989 after all the discounts (35% for suspension parts, 15% for the differential brackets, and almost $300 in GM rewards). I'm excited. Parts should show up over the next 2 weeks. On the ropes with the Cognito Comfort Ride torsion bars and leaf springs. I'll keep an eye out for any Black Friday deals for these. Also need to order new shocks. Shock Surplus recommends the Fox 2.5 Performance HTO shocks. I need to look into these to see how they compare with the Fox 2.0 shocks. I had the 2.0 shocks on my Ram and it certainly improved the ride quality, but I felt like the truck floated a bit at highway speeds. Cornering seemed to take a hit with the 2.0's. If these 2.5 HTO shocks improve on that, I'm in. Otherwise, I'll look at other options.

Thanks! That's what I was assuming. Couldn't imagine GM would go off script with the heavy duties for a single trim package. Ok... time for me to start ordering parts! Most likely won't do the install until late Feb or early March (bonus time) when I can order new wheels and tires. But I want to take advantage of the GM discount on suspension parts this month including free shipping to the local stealership.

Not sure as I don't have the other parts in hand. But I'd imagine anyone doing this change would then need to purchase new torsion bars as well. That could be the case, but I don't recall seeing that mentioned anywhere.

So... I just got the following response from Cognito: "the AT4X/Zr2 2500 doesn't share components with the the AT4/Trailboss trims. Wherein we only have a super stock package that only adds droop travel." This is incredibly disappointing to learn, but I'm left very confused. The main differences between the AT4 and AT4X (ZR2) are different knuckles, upper and lower control arms, and the rear leaf spacers. The torsion bars aren't removed or even moved as far as I know. So why wouldn't the Cognito bars work? I guess I'll look at the torsion bars for both the AT4 and AT4X to see if there are any differences there. I naturally assumed they were the same. I say that because there's a thread on another GM forum for HD trucks where several guys have made the switch to the other parts and I don't recall anyone calling out the torsion bars as an issue.

That would make sense. Guess I need to hit them up again tomorrow as I want to start ordering GM parts before the 35% discount expires at the end of the month. Appreciate the heads up.

Really? I just emailed Cognito last week asking for recommendations on shocks. Told them I was about to convert my GMC 2500 AT4 suspension to the ZR2/AT4X parts and switch to their torsion bars and leaf springs. They didn't say anything about the setup other than. To recommend their Elite 3" lift kit with the 2.5" shocks. This will be very disappointing if you're correct.

Good to hear. One last question... what shocks did you go with? I had Bilstein's on my Power Wagon and hated how rough the ride was. Switched to Fox 2.0's and thought they were a huge improvement, but also thought they were a bit softer than I'd prefer. I'm not a fan of the stock Rancho's on my AT4.

Thanks. Is the ride better now with the new setup versus simply cranking on the torsion keys?

I'm looking to make the swap on my '24 Sierra AT4 HD. I'd love to hear about ride quality from those with the 2500 trucks that made the swap. I believe Epsilon is the only one that's made a comment on this and it was to say the ride was a bit softer for him. For those that have completed the swap, has the ride quality improved over stock? Also, would you do it again? As in, was it worth it?