The AT4 is the Sierra that looks like it belongs off the pavement: the factory 2" lift, the red recovery hooks, the skid plate, and the Rancho monotube shocks. It's still a premium truck underneath, tuned to be quiet on the highway, and the first time you take it down a rutted forest road with some speed on, the front end may be disappointing. The factory shocks end up fading under constant ruts, and quickly fade during washboard or any sort of consistent heavy use. The 6112 gives the AT4 front suspension that matches the badge. Bilstein's AT4-specific springs hold the factory lift or level it by up to 1.2", and a 2.6-inch monotube with a 60mm digressive piston keeps the truck composed when the road turns to dirt.

We take it one step further. The 6112 normally shows up as a box of loose parts: dampers, springs, spring seats, and circlips, with a note that says "spring compressor required." Bilstein's kit also reuses your factory upper mounts. We build them for you, at the height you choose, with new OE-spec upper mounts, so what shows up at your door is two finished coilovers ready to bolt in to your AT4, or save you a couple hours of labor at a shop.

How We Build Them

We build every pair to order once you choose your ride height above. On our bench:

• Set the circlips. The 6112 body has a row of numbered grooves, and where the circlip sits decides your ride height. On the AT4, Bilstein uses the same groove on both sides. We set each coilover to the setting you ordered.
• Seat the billet spring perch. The anodized aluminum spring seat sits on the circlip and carries the spring.
• Compress and install the Bilstein spring. We use a mounted, shop-grade strut compressor. This is the step that makes DIYers nervous, for good reason: a coil spring under load stores a lot of energy.
• Install a new OE-spec upper mount. The rubber in your factory mounts has been soaking up every pothole since the AT4 was delivered. Reusing tired mounts on fresh coilovers is like putting new tires on bent wheels. New mounts come on every build.
• Torque, check, label. The top nut gets torqued to spec, each coilover is checked and marked driver or passenger, and the pair is boxed together.

Why Buy Them Assembled?

• No spring compressor. Rental "clamshell" compressors are the most dangerous tool most people will ever use in a driveway. You skip that part entirely.
• No mismatched sides. A common 6112 mistake is setting the two sides one groove apart by accident, which leaves the truck leaning. Ours are set and checked as a pair.
• New mounts included. The loose Bilstein kit reuses your factory upper mounts. Ours come with new ones.
• Faster install. Assembly is the slowest part of a coilover job. With that done, the job is removing two struts and bolting in two.

Bilstein approves three settings for the AT4 V8, and we build only those: stock AT4 height, 0.6" and 1.2". Every one is measured over a stock AT4, on top of the roughly 2" front lift GMC already gave it.

How to choose: Most AT4 owners want the rake gone. Park on level ground and measure from each wheel center to the fender lip, front and rear. The difference is your rake; pick the setting closest to it. Planning a steel bumper or a winch? Go up one. If your shop has the numbers, have them call us and we'll confirm the pick: (213) 433-3616.

Matching the Rear: Bilstein 5100 or 5160?

The AT4 rear also sits higher from the factory, about an inch over a regular Sierra, so it takes its own rear shocks. The axle rides on leaf springs, which set the height; the shock just needs the right length for it. Bilstein builds a 5100 and a 5160 for this truck.

For most AT4s, the Bilstein 5100 (24-309516). Built for the AT4 and Trail Boss rear at stock height up to 1" over (27.61" extended, 17.4" compressed, 10.21" of travel), with a 46mm digressive piston in a zinc-plated monotube. On our listing it's the 1-3" option. Skip the 0-1" option (24-293471); that one is sized for a regular Sierra that sits an inch lower in back.

For an AT4 that travels far on dirt or tows, the Bilstein 5160 (25-316964). The same AT4 rear fitment with a remote reservoir that adds oil capacity, so it runs cooler and holds its damping through long washboard stretches and with weight in the bed.

Run the 5100 if:

• The rear is at factory AT4 height, or up to 1" higher
• The truck is a daily driver that sees trailheads on weekends
• You want a matched Bilstein ride front and rear

Run the 5160 if:

• You drive long desert or forest roads at speed
• You tow, or carry camping gear and a rooftop tent

When you need something else: If you've lifted the rear more than 1" over a stock AT4, call us and we'll size a shock to the setup: (213) 433-3616.

Shop the Bilstein 5100 AT4 Rear Pair (24-309516)

Shop the Bilstein 5160 AT4 Rear Pair (25-316964)

On the Road

On pavement your AT4 feels tighter: less dive when you brake, less lean through a highway ramp, and the bigger factory tires stop bouncing the nose over expansion joints. It's firmer than the factory setup. If you bought the AT4 for its highway hush and want to keep it that way, this is a trade, and we'd rather you know before the install.

Off the Road

This is the reason to buy it. The 2.6-inch body carries more oil than the factory shock and sheds heat better, so damping holds on through bigger bumps and rougher trails. The digressive valving stays firm over small, fast ripples and opens up on bigger hits, so the front tracks instead of skipping. Match the rear (see above) so the back of the truck keeps up.

The Honest Trade-Offs

• 1.2" more, at most. The AT4 already carries a factory front lift. Going further takes different control arms and a different kit; call us.
• V8 trucks only, per Bilstein's chart. Duramax and 2.7L owners: call us first.
• Your height is set when we build it. Changing it later means taking the coilover apart with a strut compressor. Measure before you order.
• Firmer than stock. See "On the Road" above.
• Built to order. Every pair is assembled for your truck, so it takes longer to ship than a box pulled off a shelf.
• Watch camber at #3. On top of the factory lift, the top setting angles the factory upper control arms further. If your shop can't bring camber into spec, aftermarket upper control arms fix it.

Install Notes

• Fits 2019-2026 GMC Sierra 1500 AT4, 4WD, 5.3L or 6.2L V8, Crew Cab or Double Cab.
• 3.0L Duramax or 2.7L turbo: call us before ordering. Bilstein's chart for this kit is written for the V8.
• Not for the AT4X. It uses Multimatic DSSV dampers and a different front suspension.
• Not for other Sierra 1500 trims. Non-AT4 Sierras use 47-293557: see our 2019-2026 Sierra 1500 assembled 6112 listing.
• Silverado Trail Boss owners: same kit, see our Silverado Trail Boss assembled 6112 listing.
• Any suspension shop can install these in the time it takes to swap two struts. The spring compressor work is already done.
• Get an alignment right after install. Any lift changes camber and toe.
• Recheck the front height after the springs settle in over the first few hundred miles.

Who Should Buy These

AT4 owners who want the front suspension to back up the look: level stance, damping that holds on dirt, and the confidence to take the long way to camp. It suits daily-driven AT4s that see trailheads, light overland builds, and owners who'd rather hand their shop two finished coilovers.