Key Features:

• Progressive Design:
  • Replaces the factory lower overload leaf with 6 thinner gauge leaves, significantly improving ride quality while maintaining OEM load capacity.
  • Designed to eliminate the harsh rebound of the factory overload spring, allowing for smoother handling of medium to large bumps when paired with a Carli Suspension System.

• Lift Block Included:
  • This kit comes with a lift block to ensure the rear is properly leveled with the front of the 4.5″/5.5″ Carli Systems.

• Enhanced Ride Quality:
  • The Progressive Add-a-Pack replaces the 1″ thick lower overload spring, which doesn’t follow the contour of the rest of the pack. This modification results in:
    • Predictable Spring Rate: The truck’s load capacity remains unchanged, leading to a smoother engagement and disengagement of the springs.
    • Improved Traction: A more predictable rear spring rate enhances both ride quality and traction, especially when loaded.

• Performance Differences:
  • While the rear may sit lower under heavy loads, it will ride better compared to stock setups.

Compatibility for F250 and F350:

• F250 Systems:
  • The F250 has a lighter rate spring pack than the F350, making the Add-a-Pack a beneficial upgrade over stock.

• F350 Systems:
  • The F350 with the Add-a-Pack may still feel quite stiff, as the main pack does not flex much unless loaded. We do NOT recommend these for F350 models due to potential stiffness issues.

Optimal Recommendations:

• For the best ride quality, we recommend the Full Replacement Leaf Spring Packs for both the F250 and F350, especially for the F350, which has very stiff factory springs.
• If Load Capacity is a Concern:
  • Consider pairing the Full Progressive Leaf Springs with an aftermarket airbag system to restore the F350’s capacity.
  • For the 4.5″/5.5″ lift, we offer Long Travel Airbags.
  • For 2.5″/3.5″ heights, choose a system that allows airbags to disconnect from the lower mount during suspension cycling, ensuring full rear suspension travel.