2019-2024 GM 1500 Trail Boss / AT4 6" Big Lift Kit w/ Falcon 2.1 Shocks (44-39621)

Description

ReadyLIFT's reengineered 6" Big Lift Kit for the 2019-2024 Chevy Silverado 1500 Trail Boss and GMC Sierra 1500 AT4 adds 6" on top of the factory 2" lift. Heavy-duty angled and offset top mount strut extensions realign the struts, and a lower mount pre-load spacer slightly raises spring rate for larger wheels and tires. The engineering updates developed for the 2025 trucks carry over, with redesigned steering knuckles, retained factory Auto 4WD and revised geometry to help prevent driveline vibration. Fabricated rear blocks and an add-a-leaf lift the rear, paired with new Falcon 2.1 Monotube rear shocks.

Part Number: 44-39621 (supersedes 44-39620)

Features

• Proprietary lower strut clamshell design maintains factory geometry and retains the factory strut
• Tube steel upper control arms with maintenance-free pivot bushings and 1-ton ball joints
• 3/16" thick steel plate cross members and full-width skid plate
• Anti-torsion boxed and gusseted plate steel differential drop brackets
• Fabricated steel 5" rear lift blocks with integrated bump stop landings and offset pin for proper pinion angle
• Rear add-a-leaf for an additional 1.5" of lift
• Falcon 2.1 Monotube extended-length rear shocks (2.3" aluminum body, 3/4" shaft)
• Redesigned steering knuckles for an improved turning radius
• Retains factory Auto 4WD functionality
• Revised suspension geometry helps prevent driveline vibration
• Includes ReadyGuard Powertrain Warranty

Tire Fitment:

• Recommended max tire with no trimming: 20x9 0 offset - 37x12.50 tire
• *Max with trimming: 20x10 -18 offset - 37x12.50

Notes

• Use of Auto 4 Hi feature not recommended
• Not compatible with rear mono-leaf springs
• Single Cab configuration has not been validated for fitment & drivability by ReadyLIFT
• Not for use on diesel applications (no oil line relocation bracket included)
• Late 2024 trucks with round rear U-bolts require U-bolt kit 67-35150UB