2025 3.0L Duramax 4” ReadyLift Big Lift Kit (44-35400)

Fits

Boost the off-road capabilities of your 2025 Duramax 1500 with ReadyLift's heavy-duty Big Lift Kit. This kit delivers serious strength with 1/4-inch boxed steel differential drop brackets. Each bracket is reinforced with double gussets and a center rib for added durability. They're built to handle the twisting forces of the front differential under real off-road pressure.

The Heavy-duty angled and offset strut extensions keep geometry in check and shocks working at peak performance, while a pre-load spacer ups the spring rate to manage the extra heft of oversized wheels and tires. In the rear, fabricated steel lift blocks with integrated bump stop landings and new rear shock extensions keep the factory shocks doing what they do best.

Part Number: 44-35400

• Adds 6” total lift (4” kit + factory 2”)

• Fits 35x12.50 tires on 9” wheels, 0 offset (no trimming)

• Keeps factory struts with clamshell design

• 3/16-inch-thick steel plate cross members and skid plate
• Anti-torsion boxed and gusseted plate steel differential drop brackets
• Includes Ready Guard Powertrain Warranty
• Passenger Knuckle
• Driver Fabricated Block
• Pass. Fabricated Block 
• Rear Brake Line Bracket
• Rear ABS Bracket
• CV Axle Spacer
• Rear Shock Extensions
• Rear Shock Extension Washers

•  Recommended max tire with no trimming: 20x9 0 offset - 35x12.50 tire
•  Recommended max tire with trimming: 20x10 -18 offset - 35x12.50 or 325/60R20
• Trimming requirements for larger than recommended wheel/tire include front valance, front felt liner edge, rear felt liner edge, and front rear well edge mud flap
• When lifting a vehicle and installing aftermarket wheels and tires, a tire manufacturer's construction and material quality can alter vehicle ride quality. When increasing a vehicle wheel and tire size, most larger aftermarket truck and SUV tires are 10-ply (or more) E tires compared to typical OEM 6-ply C tires.
• SAEJ2492 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.

Installation Instructions