ReadyLIFT 2.0" SST Lift Kit | +2.0" Front (~4" Total w/ Factory Lift) / 1.0" Rear | Billet Aluminum Strut & Preload Spacers | Tubular UCAs w/ 1-Ton Ball Joints & TCT Bushings | 2019–2023 GMC Sierra AT4 & Chevy Silverado Trail Boss | SKU: 69-3920

Verified Fitment

Does NOT fit:

• GMC Sierra AT4X — different factory suspension.
• Chevrolet Silverado ZR2 — different factory suspension.
• Vehicles with rear composite mono-leaf springs — this kit requires traditional square-U-bolt steel leaf springs (mono-leaf is identifiable by a round/circular U-bolt around the top of the leaf spring).
• Late-model 2024/2025 trucks with round U-bolts as-is — require U-bolt kit 67-35120UB for 2025 compatibility.

Additional cautions:

• Use of the Auto 4 Hi (4Auto) feature is not recommended with this kit.
• Not intended for off-road use or abuse.

Purpose-built for factory-lifted trucks: The AT4 and Trail Boss already carry a factory 2" front lift with longer strut assemblies. A generic leveling kit on these trucks binds the factory ball joint and contacts the lower strut/CV axle. This kit is engineered to work with that factory lift — not against it. Confirm your rear spring type (square vs. round U-bolt) before ordering; text (469) 407-7538 with a photo if unsure.

Component Specifications

Works with the factory lift — engineering distinction: Rather than stacking a leveling spacer onto trucks that are already lifted (which binds the factory ball joint and risks lower strut/CV contact), the 69-3920 uses a top-mount billet strut spacer plus a preload spacer to add 2" on top of the factory 2" — netting ~4" of front lift while keeping the factory strut architecture intact. It's the same concept as ReadyLIFT's TRD Pro "Plus 2" approach for factory-lifted trucks.

Tubular UCAs with 1-ton ball joints — engineering distinction: The added front lift moves the ball joint past the factory arm's range. The tubular UCAs with heavy-duty 1-ton ball joints and maintenance-free TCT bushings restore correct pivot geometry at the new height — the same premium arms found in ReadyLIFT's 66-3921 leveling kit.

Rear rake by design: The 3" cast iron rear blocks against the ~4" front leave a subtle factory-style rake that holds under towing or payload and suits the AT4/Trail Boss body lines.

What Is and Is NOT Included

Critical Compatibility

AT4 and Trail Boss only. This kit is purpose-built for the factory-lifted 2019–2023 Sierra AT4 and Silverado Trail Boss. It is not for standard 1500 trims (those use different kits), nor for the AT4X or ZR2.

Requires square-U-bolt leaf springs. Compatible only with traditional steel leaf springs identified by square U-bolts. Composite mono-leaf springs (round/circular U-bolts) are not compatible.

Round-U-bolt 2024/2025 gate. Late-model round-U-bolt trucks require the 67-35120UB U-bolt kit to fit.

4Auto not recommended. ReadyLIFT does not recommend using the Auto 4 Hi feature with this kit.

ADAS recalibration required. GM Safety Alert Seat, Lane Keep Assist, and Forward Collision Alert must be recalibrated after install.

Wheel & Tire Fitment

Max tire size differs between the two trucks. Figures are based on Wheel Pros wheels and Nitto tires; dimensions vary by manufacturer, so every tire-and-wheel combination must be test fit before final installation.

Ride quality note: Stepping up to heavier all-terrain or mud-terrain tires changes the ride. Most larger aftermarket AT/MT tires are 10-ply (Load Range E) versus a typical OEM 6-ply (Load Range C). The stiffer sidewall increases the perception of suspension stiffness often described as ride harshness, and ride, handling, traction, noise, fuel economy, and wear differ meaningfully between All-Season, All-Terrain, Mud-Terrain, and Trail-Terrain tires. Tire and wheel choice will have a real impact on how the lifted truck drives — factor it in.

Installation Notes

Skill level: Advanced — a complete bolt-on system (billet strut and preload spacers, UCAs, rear cast blocks, bump stop cups). No cutting or welding, but the alignment-critical UCA work makes professional installation the recommended route. Estimated install time ~4.5 hours (±0.5 hr), excluding alignment and wheel/tire assembly.

Tools required: Standard hand and socket tools, torque wrench, spring compressor as needed for the strut assembly, ball joint separator. Alignment shop access required after installation.

Confirm rear spring / U-bolt type first. Verify square-U-bolt steel leaf springs before ordering — mono-leaf (round U-bolts) is not compatible, and round-U-bolt 2024/2025 trucks need 67-35120UB.

Post-installation alignment is mandatory. A professional 4-wheel alignment is required to verify torque specs, confirm ride height, and lock in the corrected UCA geometry.

ADAS and headlamp recalibration. GM Safety Alert Seat, Lane Keep Assist, Forward Collision Alert, and headlamp aim must be checked and recalibrated after installation.

SAE J2492 Safety Warning: By installing this product, you acknowledge that the suspension of this vehicle has been modified. As a result, this vehicle may handle differently than factory-equipped vehicles. As with any vehicle, extreme care must be used to prevent loss of control or rollover during sharp turns or abrupt maneuvers. Always wear seat belts, and drive safely, recognizing that reduced speeds and specialized driving techniques may be required. Failure to drive this vehicle safely may result in serious injury or death. Do not drive this vehicle unless you are familiar with its unique handling characteristics and are confident of your ability to maintain control under all driving conditions. Some modifications (and combinations of modifications) are not recommended and may not be permitted in your state. Consult your owner's manual, the instructions accompanying this product, and state laws before undertaking these modifications. You are responsible for the legality and safety of the vehicle you modify using these components.

Common Questions

Why do AT4 and Trail Boss need a special kit instead of a normal leveling kit?
Because they already come with a factory 2" front lift and longer strut assemblies. A generic leveling kit stacked on top binds the factory ball joint and can contact the lower strut and CV axle. The 69-3920 is engineered to work with that factory lift, adding 2" the right way for ~4" total front height.

What's the total lift I end up with?
This kit adds 2" of front lift on top of the factory 2", for roughly 4" of total front elevation, plus 1" of rear lift from the 3" cast blocks netting against the factory rear height.

Will it fit my AT4X or ZR2?
No. The AT4X and ZR2 use different factory suspension and are excluded. This kit is specific to the AT4 and Trail Boss.

How do I know if my rear springs are compatible?
Look at the U-bolt on top of the rear leaf spring. Square U-bolts = traditional steel leaf springs = compatible. Round/circular U-bolts = composite mono-leaf = not compatible. Separately, some 2024/2025 trucks use round U-bolts and need the 67-35120UB kit. Text (469) 407-7538 a photo if you're unsure.

Do I need an alignment afterward?
Yes — mandatory. The UCAs change camber and caster, so a professional 4-wheel alignment plus ADAS recalibration is required after install.

The Obsidian Take

The 69-3920 is ReadyLIFT's purpose-built "Plus 2" SST kit for the 2019–2023 Sierra AT4 and Silverado Trail Boss — the two GM 1500 trims that leave the factory already lifted 2" up front. It adds 2" more front and 1" rear on billet spacers and cast blocks, with tubular UCAs and 1-ton ball joints included.

The reason this exists as its own kit is the factory lift. The AT4 and Trail Boss ship with longer strut assemblies and a 2" front raise, and stacking a normal leveling kit onto that binds the factory ball joint and risks lower strut and CV contact. ReadyLIFT's answer is a top-mount billet strut spacer plus a preload spacer that limits droop — adding height while keeping the factory strut architecture intact. It's the same philosophy as their TRD Pro "Plus 2" kit for factory-lifted Tundras.

The UCAs are the geometry half of the equation. The extra lift takes the ball joint past the factory arm's range; the tubular arms with 1-ton ball joints and maintenance-free TCT bushings bring the pivot back into spec — the same premium arms in ReadyLIFT's 66-3921 leveling kit. Combined with the 3" rear blocks, you get a ~4"/1" stance with a factory-style rake.

The fitment trap is the rear spring. This kit needs traditional square-U-bolt steel leaf springs; composite mono-leaf (round U-bolts) won't work, and round-U-bolt 2024/2025 trucks need the 67-35120UB kit. Check the U-bolt before you buy.

This SKU is for: 2019–2023 Sierra AT4 and Silverado Trail Boss owners on square-U-bolt steel leaf springs who want ~4" of total front lift done correctly on their factory-lifted trucks — with corrected UCA geometry, 1-ton ball joints, and room for a 305/55R20 (AT4) or 295/65R20 (Trail Boss).

This SKU is NOT for: AT4X or ZR2 trucks, standard non-AT4/Trail Boss 1500s, composite mono-leaf trucks, round-U-bolt 2024/2025 trucks without the 67-35120UB kit, off-road/abuse use, or anyone planning to skip the post-install alignment and ADAS recalibration.

Closing Blocks

Manufacturer Data Disclaimer
Product specifications, fitment data, and feature details are sourced from ReadyLIFT Suspension manufacturer documentation and verified third-party technical references current at the time of publication. ReadyLIFT reserves the right to modify product specifications without notice. Confirm trim (AT4/Trail Boss vs. AT4X/ZR2), model year, and rear spring/U-bolt type (square steel leaf vs. round mono-leaf) before ordering. OFAS is not responsible for incompatibility resulting from AT4X/ZR2 misapplication, non-AT4/Trail Boss trim misidentification, mono-leaf or round-U-bolt spring configurations ordered without the required U-bolt kit, or failure to complete post-installation alignment and ADAS recalibration. Obsidian Forged Auto Supply is an authorized ReadyLIFT dealer.

Prop 65 Warning
⚠ WARNING: This product can expose you to chemicals known to the State of California to cause cancer and birth defects or other reproductive harm. For more information, go to www.p65warnings.ca.gov.

Non-Returnable Notice
This item is non-returnable once installed. Verify trim, model year, and rear spring/U-bolt type before ordering. Questions before ordering? Text (469) 407-7538.