GMCnewbie

They are pricey for sure. I think i got them for $100 off from ShockSurplus.com a few months ago. Not a great deal, but it covered the Texas sales tax. I pulled the trigger simply because I was so fed up with how rough my ride was that I was willing to do just about anything to improve it. My wife hated the ride as well and urged me many times to simply trade it in for something else. I was very tempted to do it right up until I started taking the front end apart. Carvana was offering me $70k for my truck in March which was $2k more than I paid for the truck a year ago. The thing that kept me from selling was that Ford F250s are grossly overpriced and all of the local Ram stealerships around Houston have the worst service departments. So I decided to tear into this truck in hopes of improving ride quality. I'm very pleased with the initial results. Fortunately I don't have a need to max out my towing or payload capacities allowing me to run the Cognito torsion bars and leafs. They still offer enough capacity for my needs.

That is correct. But we haven't quite gotten to the always hot/humid days yet. That usually kicks in around late May. We're still in the rainy season right now. As for my stock Rancho shocks being blown, who knows. They were crap from day one and replaced at only 5k miles with the Fox HTO shocks. I saw the same video you mentioned regarding the 5100 review. It was an impressive change for sure.

I completed the front swap (control arms, knuckles, differential carrier bars, torsion bars, and shocks). I haven't completed the rear swap, yet, as I've been traveling so much for work over the last 2 months. That combined with me being an idiot and failing to order enough LCA bolts and U-bolts to complete the jobs. I was only able to complete one side of the rear last weekend as I mistakenly only order 2 U-bolts initially. I've been in NYC all week for work. I'm hoping to complete the rear-end on Sunday. New wheels and tires are in my garage waiting for me to complete the full suspension swap. I didn't want to swap wheels until I finished everything so I could get a sense of how ride felt versus stock. I drove the truck for about a month with just the front suspension swapped and loved it. The rear had the new shocks but nothing else. The truck handled large dips and bumps with ease. No more jarring rebounds or excessive bouncing. I can now ride over decent sized speed bumps without coming to a stop first. In short, I absolutely love the new ride. I'm hoping the rear swap (including the Cognito leafs) will further enhance the ride quality. I will swap the wheels once I get the rear completed and ride height dialed in. Fingers crossed that happens this Sunday. I haven't checked the weather in Houston lately.

I went with the new Fox 2.5 HTO shocks along with the Cognito torsion bars on my gasser. The ride is so much better now when hitting speed bumps or anything else in the roads. I've never used the Bilstein 5100's. I've heard their fairly stiff which is why I didn't go with them this time around. I had the 4600's on a pair of Rams from the factory and hated them on both trucks. I wasn't a fan of the Fox 2.0 shocks, but they greatly improved ride quality over the 4600's on my old Power Wagon.

I'm not saying they aren't GM bars, but the markings on the bars are not the same between the stock 4800 bars and the Cognito bars that I installed on my truck. Im also interested in finding out the actual ratings on these bars. My front end has noticeably smoother ride now.

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.

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.

I've heard 1.5" as well. I honestly never asked the question as to suspension vs tire size. What I can say is the AT4X/ZR2 components combined with Cognito torsion bars, stock keys, and stock AT4 wheels/tires gave me a 1" lift in the front.

I set them to the same point as stock. That gave me roughly 1" lift with stock wheels and tires. I haven't gone back to adjust because I'm too lazy to lift the truck again right now. I think the Cognito keys would've settled lower than the 4" had i tried driving around with it to get the suspension to settle. I may try that down the road depending on how things shake out with the new wheels/tires.

I finally wrapped up the front end and took the truck out for a ride. For reference, I replaced UCAs, LCAs, knuckles, differential carrier brackets, torsion bars, and shocks. I'm still waiting on a part for the rear-end. That said, the ride feels good. It's a much more controlled ride over speed bumps, dips, and humps in the road. The ride feels much nicer. Is it worth the price paid? Time will tell. Still waiting for my new wheels and tires as the wheels are backordered. Hoping they'll arrive in the next few weeks. I still need to dial-in the lift in the front, but i think I'm gonna wait until the wheels and tires get here before I try to make any final adjustments. On that note, I initially installed Cognito torsion keys with the new bars (per the Cognito rep), but the front height was about 4" higher than stock. So I swapped them out for the stock keys and that was about 1" lift over stock. I'll play around more with the height when the wheels/tires get here.

I'm assuming you're referencing bolts and nuts. For that, the only bolts/nuts that I'm aware of that need to be replaced are the LCA bolts and the axle nut. Both are expensive. I strongly suggest ordering online to save money.

I would guess so. I don't believe the diff carrier brackets give much of a drop from what I could tell holding the bars next to each other. Someone else here might have better details on the true differences between the two brackets as I was exhausted by the time I got to the carrier brackets.

The other thing I'll add quickly to this is that I did all the work by myself. My son helped for a few hours one day grabbing tools and drinks for me, but I did all the heavy lifting. I wish I had an extra set of hands and another set of eyes on this. That would've helped make this job a lot easier as the parts are not light at all. And I struggled with removing a few pieces because I wasn't looking at something in the right light. I eventually got to the right place, but I had to step away and reset to get there.

I've seen that comment as well about ripping out the hitch. I was under the truck on Sat and didn't get the sense that I needed to go that far with it. You do have to remove the spare tire though to get to one of the shackle bolts. I'm hoping that's all I need to do. Regardless, I'm in for whatever's needed at this point. I just want to get it done. lol You're not wrong with that line of logic. I chose not to go with the aftermarket lift specifically because of the geometry involved with the steering and axles. I've read that just doing the UCAs with lifts has a greater potential for causing issues down the road with failures in those areas. Again, I don't have first hand experience to speak to that, but the comments I read spooked me enough to go the full swap route instead. At the end of the day it's your truck right. They're selling a ton of kits. I can't image they're terrible or anything. I honestly only wanted a minimal lift to clear larger tires. I'd love to go with a 3-4" lift, but my wife is 5' tall and struggles getting in and out as it is. lol

That's absolutely correct. I have zero experience with butt-in-seat with either the comfort ride leafs or mini-packs. I chose the comfort ride leafs as it wouldn't require me to take apart the leaf pack. I'm just replacing the entire setup. Much easier in my mind. I've spent the last 4 days under and around my truck working on the complete suspension swap. This project is not for the faint of heart for sure. I've done a suspension swap on my wife's Expedition 2 years ago and assumed this would probably be a little more difficult because of the leafs and torsion bars. Man was I wildly off the mark on that assessment. This has been a beast. That said, it's not the worst job in the world assuming you're technically capable and have all the right tools readily available. I have completed the majority of the work, but I'm waiting on Fox to ship me mounting bolts for my new shocks (they failed to include them in the boxes). So the front end is just waiting on those bolts, which should be here tomorrow, and I'll be able to wrap that up. I'm also waiting on the leaf spacer as I somehow forgot to add that to my order back in Oct. So for now I've installed the new shocks in the back and will do the leafs and other parts in the rear in another week or so when the parts arrive. I will share what I consider helpful tips and tricks in the next few days. I'm mentally beat at the moment and want to get the shocks installed and the truck running before making the list. My hope is these items will help the job go a little easier for anyone else considering this project. There's been a lot of trial and error for me on this one as I've never owned a truck with torsion bars or leafs before.

I can confirm the LCA bolts are TTY and are listed as single-use on the GM Parts sites. That said, I'm not a super smart engineer type that can explain what would happen if you reuse the bolts. I just replaced mine as part of a large suspension job. Those bolts are freaking expensive if you wait until the last minute to buy them. I think you can order them on Tasca.com and other sites for about $9 per bolt. GM lists them at $13 and change. The local dealers in Houston are price gouging for parts now and got me for $23 per bolt. Gotta love it.

This is not completely true. I spoke with someone a few weeks ago when I ordered my comfort ride torsion bars and leaf springs. They said the bars will work, but it requires you to purchase new torsion keys. It would be great if they mentioned that on their site. The SKU for the Cognito keys is 110-90771. I plan to start the install process tomorrow morning for my swap. I went with the Fox 2.5 HTO shocks for my truck. No clue how good they are. I had the Fox 2.0 shocks on my Power Wagon and liked them. The advertising claims the 2.5 HTOs offer more control for these trucks. We'll see how it goes.

Here's the other images of the Cognito sticker. Nothing really helpful to identify the spring rate.

Confirmed that my truck has the 4,800lb bars installed. I took photos of both the Cognito and stock bars. The Cognito bars only had a single sticker that was wrapped around them. I had to take 3 pics to get the whole thing. The Cognito bar is 1.02mm smaller than the stock bar.

I haven't been outside to look at my truck. My guess was 4,600lb on the stock bars, but you're probably correct with 4,800lb. My torsion bars are the lightest available from GM whatever that is. I have a digital caliper and will measure the Cognito bars tomorrow afternoon for you.

I have them in the garage now, but I'll have to check the measurements tomorrow. That said, my AT4 has the 4,600lb torsion bars. I want to say the Cognito bars are rated at 3,700lb. I could be wrong on that, but I seem to recall reading that somewhere.

They're the rear jounce spacers (85565250). Based on the parts diagrams, the AT4X doesn't used them which is confusing since all other parts are the same with the ZR2. Forgot to answer your initial question. Yes, full swap is in order here. Replacing the UCA, LCA, knuckles, shocks, leafs, leaf spacers, and torsion bars.

Finally gonna do the suspension swap on my '24 AT4. Parts have been sitting in my garage since mid-Nov. Weather should be nice next weekend. New wheels/tires are on order and should be here in the next week or so. I also went ahead and bought the Cognito Comfort Ride torsion bars and leaf springs. Not sure what to expect from all of this, but I'm excited to dig into this project. I decided to do the Cognito parts simply because I don't plan to haul super heavy loads anytime soon. A 22% loss in capacity shouldn't affect my usage much at all. That and the fact that I got a really good deal on my truck last year from the dealer that even after ordering all these parts and wheels, my out-the-door price on the truck and parts included is still less than MSRP. That's how I'm gonna justify it in my head at least. lol I'll post pics next week when it's all wrapped up. On a side note, I apparently ordered a pair of the rear suspension spacers that for the Zr2 only according to the GM parts diagrams. I clearly wasn't paying attention when I placed my order. Let me know if anyone needs/wants them. I think I paid around $100 for the pair. Not sure what GM is charging for them these days.

I looked up the new part numbers you found and came away confused as well as one GM parts site claims the parts don't fit the '24 or '25 model year Sierra HDs while other sites claim they do. I'd suggest calling your local dealer and asking the parts guys to advise which part number are correct for your truck.

I can't speak to the new part numbers you found, but I purchased the original part numbers for my truck that you have listed -- 85144996, 95144997, 85144990, and 85144991. I'll look them up again today to see what I can find. Note: just remembered you have a '25 model. I'm pretty sure no changes were made to suspension with the new model year, but they could've made slight changes to those two parts specifically. I recall one of the guys here mentioning there was a change to the knuckles between i think the '22 and '23 years or possibly the '23 and '24 years. Can't remember which.