Zone Offroad ZONC6159 Rear Add-A-Leaf Kit for 1999-2018 Silverado/Sierra 1500

Vehicle Fitment

• 1999-2018 Chevrolet Silverado 1500 (2WD/4WD, All Engines)
• 1999-2018 GMC Sierra 1500 (2WD/4WD, All Engines)
• 1999 Chevrolet K1500 (2WD/4WD, All Engines)
• 1999 GMC K1500 (2WD/4WD, All Engines)

Fitment Notes

• Fits both 2WD and 4WD configurations across all supported model years
• Designed for single rear wheel (SRW) models only - not applicable to dually configurations
• Does NOT fit 2019 and newer Silverado 1500 or Sierra 1500 models - the center pin diameter on these trucks (7/16") is larger than the kit's center pin hole (3/8"), making this kit incompatible without modification
• Actual rear lift height will vary between approximately 1.5 and 2 inches depending on the condition and sag level of the factory rear spring pack
• Long, thin add-a-leaf design must be inserted into the factory spring pack in the correct position by length - refer to included installation instructions for correct placement
• Compatible with all engine variants across supported model years

Features

• Long, thin leaf spring design distributes load and lift across a greater span of the spring pack, providing a smoother, more compliant rear ride compared to shorter add-a-leaf designs that cause a harsher step in spring rate
• Adds approximately 1.5 inches of rear lift height to help level the stance of trucks equipped with front leveling or lift kits, or to restore sagged factory rear springs to their original or improved ride height
• Increases rear load capacity and reduces rear sag under load - ideal for trucks that regularly haul cargo, tow trailers, or carry heavy equipment
• Neoprene tip pads on the ends of each leaf reduce leaf-to-leaf contact noise and friction within the spring pack, maintaining a quiet ride after installation
• Steel construction with black powder coat finish for corrosion resistance and long-term durability against road salt and moisture
• Engineered and manufactured in the USA by Zone Offroad, a division of Sport Truck USA / FOX Factory
• Backed by Zone Offroad's 3-year / 36,000-mile warranty and limited lifetime warranty against defects in materials and workmanship

Specifications

• Rear Lift Height: Approximately 1.5-2 inches (varies with factory spring condition)
• Position: Rear
• Style: Long add-a-leaf
• Leaf Width: 2-1/2 inches
• Leaf Length: 38-3/8 inches
• Pin Size: 9/16 inch
• Center Pin Size: 3/8 inch (0.375 inch)
• Free Height: 6.75 inches
• Material: Steel
• Finish: Black powder coat
• UPC: 711745597518
• Quantity: 2 add-a-leafs (sold as a pair)

Included Components

• 2x Long Add-A-Leaf Springs (one per side, left and right)
• 2x Center Pins
• 2x Alignment Clamps
• 1x Installation Instructions

Product Description

The Zone Offroad ZONC6159 is a rear long add-a-leaf kit designed for 1999-2018 Chevrolet Silverado 1500 and GMC Sierra 1500 trucks in both 2WD and 4WD configurations. It adds a pair of long, thin steel leaves into the existing factory rear leaf spring pack to increase spring rate, raise rear ride height by approximately 1.5 to 2 inches, and improve the truck's ability to carry heavier loads without sagging. Unlike shorter add-a-leaf designs that create a harsh, abrupt step in spring stiffness, Zone Offroad's long thin design spreads the rate change across more of the leaf pack length - resulting in a progressive feel that better preserves ride quality under normal driving conditions while still providing meaningful support under load. Neoprene tip pads at each end of the leaves prevent metal-to-metal contact and eliminate the squeaking or tapping that shorter leaves can introduce when they shift within the pack.

This kit is particularly well suited for Silverado and Sierra 1500 owners who have installed a front leveling or lift kit and want to raise the rear to match, for trucks used regularly for towing or hauling that experience excessive rear squat under load, or for older trucks where the factory rear springs have sagged over time and partially lost their original ride height. The actual lift achieved will vary between 1.5 and 2 inches depending on how much the factory spring pack has already settled - trucks with fresh or minimally sagged springs will see closer to 1.5 inches, while trucks with well-worn packs may see closer to 2 inches as the add-a-leaf restores more height. An important compatibility note: 2019 and newer Silverado/Sierra 1500 trucks changed to a larger 7/16-inch center pin, which is incompatible with this kit's 3/8-inch center pin hole without drilling out the leaves - the confirmed fitment range is 1999-2018 only.

The ZONC6159 is sold as a complete kit for both sides - two long add-a-leaf springs, center pins, and alignment clamps - along with easy-to-follow installation instructions. Installation requires disassembling the rear axle U-bolt plates and spreading the factory leaf pack to insert the add-a-leaf in its correct position by length. Most owners complete this install with basic tools and a floor jack, though professional installation is an option for those without experience working on rear suspension. As with all Zone Offroad products, the ZONC6159 is backed by a 3-year / 36,000-mile warranty and a limited lifetime warranty against defects in materials and workmanship.