2025-2026 GM 1500 Trail Boss / AT4 4" Big Lift Kit (44-35425)

The ReadyLIFT 4-inch Big Lift Kit is a new offering engineered for the 2025 Chevy Silverado Trail Boss and GMC AT4 1500 trucks, delivering incredible ride quality and superior handling performance. This kit is built with the very best of ReadyLIFT engineering, featuring heavy-duty components such as boxed steel front and rear cross members and a full-width front skid plate constructed of thick 3/16-inch plate steel. The result of months of development and thousands of miles of road and trail testing, this 4-inch lift kit is proven to make these GM 1500 trucks ride better than stock.

Features

• Delivers 4 inches of lift.
• Maintains the factory ride and handling characteristics.
• Features heavy-duty angled and offset top mount strut extensions and rear shock extensions.
• Includes heavy-duty cast iron lift knuckles engineered to retain factory-quality geometry.
• Utilizes boxed steel front and rear cross members and a full-width front skid plate made from 3/16-inch plate steel.
• Comes with 1/4-inch boxed plate steel differential drop brackets with a double gusset and boxed center rib.
• Includes fabricated steel rear blocks with integrated bump stop landings.
• Backed by the ReadyGuard Powertrain Warranty.

Notes

• Use of the Auto 4 Hi feature is not recommended.
• Vehicle alignment and headlamp aim must be checked and adjusted after product installation.
• If the vehicle is equipped with Advanced Driver Assistance Systems (ADAS), these systems may require recalibration.
• Estimated installation time is 10 hours plus or minus 1 hour, excluding alignment and wheel/tire assembly.
• Do not recommend an 18-inch wheel with 0mm offset or higher due to fitment issues; only a -12mm offset works for an 18-inch wheel.

Compatibility Notes

• Engineered for 2025 Chevy Silverado Trail Boss and GMC AT4 1500 trucks.
• Not for use on Diesel motor applications.
• Not compatible with rear composite mono-leaf springs; only works with vehicles equipped with traditional steel leaf springs.
• Single Cab configuration fitment and drivability has not been validated.

Tire Fitment

• Recommended maximum tire with no trimming is 35x12.50 on a 20x9 wheel with 0 offset.
• With trimming, fitment is possible for up to 35x12.50 or 325/60R20 tires on a 20x10 wheel with -18 offset.
• Trimming requirements include the front valance, front felt liner edge, rear felt liner edge, and front-rear well edge mud flap.

Specs

• Lift Height: 4 inches.
  
• Cross Member Material: 3/16-inch plate steel.
  
• Differential Drop Material: 1/4-inch boxed plate steel.
  
• Kit Contents: Front/Rear Cross Members, Front Skid Plate, Lift Knuckles, Strut Extensions, Rear Shock Extensions, Differential Drop Brackets, Sway Bar Drop Brackets, Fabricated Rear Blocks, and installation hardware.