17-23 FORD F250/F350 ADD-A-PACK, REAR BUMP DROPS, & 2" BLOCK, 4.5"

Progressive Add-a-Pack Rear Springs

Our 6-leaf progressive add-a-pack rear springs are a proprietary design built for us by Deaver Spring MFG. The lower overload leaf is removed and replaced with 6 thinner gauge leaves. The O.E.M. load capacity is maintained while improved ride quality is achieved. This kit includes a lift block to achieve the proper lift to level the rear to the front of the 4.5″/5.5″ Carli Systems.

These packs are designed to eliminate the harsh rebound of the factory overload spring they replace, helping to tame medium to large bumps when paired with a Carli Suspension System. The Progressive Add-a-Pack replaces the lower overload spring on the factory pack (the 1″ thick leaf that doesn’t follow the contour of the rest of the pack). By removing this spring “wall” and replacing it with a mini progressive leaf pack, the truck’s capacity remains unchanged, while the rear spring rate progression becomes much more predictable. Engagement and disengagement of the spring are smoother, increasing ride quality and traction. As the “wall” is removed, the rear may sit lower with a heavy load but will ride better when loaded.

The rear of the Super Duty can be outfitted with either a replacement Full Progressive Spring Pack (reduces capacity to a “light” ¾-ton) or this factory leaf-pack modifying Progressive Add-a-Pack. F250 and F350 trucks differ slightly: since 2008, the F250 has a lighter rate spring pack than the F350. The F250 Add-a-Pack systems are a nice improvement over stock, while the F350 with Add-a-Pack remains very stiff and is not recommended for installation.

For optimal ride quality, we recommend Full Replacement Leaf Spring packs for both trucks, especially the F350 given the super-stiff factory springs. If capacity is a concern, an aftermarket airbag system should be installed to complement the Full Progressive Leaf Springs and restore F350 capacity. In the 4.5″/5.5″ range, we offer our Long Travel Airbags. For 2.5″/3.5″ lift heights, we recommend a system that allows the airbags to disconnect from the lower mount during suspension cycling to take full advantage of rear suspension travel.