Rusty's FSJ 3.5" - 4" Full Size Spring Pack Lift Kit


  • Brand: Rusty's Off Road Products
  • Availability: In Stock
  • Part Number: RK-350SP-FS-RX1

Some suspension companies claim nothing has improved in the manufacturing of leaf spring in 25 years. Well not at Rusty's! While other companies continue to offer a 4 inch FSJ spring that was designed back in the 70's, many things have improved in the spring industry. Rusty's has incorporated many of these improvements in our FSJ springs, which are built in North America.

The 4" lift front springs are constructed with 4 leafs that feature tapered leafs ends and anti-friction pads for a smooth ride. The leafs are shot-peened to further reduce stress and increase spring life. Only the best in rubber bushings are used, and the Rusty's front springs have a 310 lbs. spring rate. There is not a better spring pack built today.

The rear springs are a 6 leaf design with tapered leafs ends and anti-friction pads that reduce inter-leaf friction. Like the fronts, they are also shot-peened to reduce stress and increase spring life. Each spring is load-tested to ensure they meet the required specifications. The Rusty's rear springs have a 400 lbs. spring rate. Spring eye bushings and Grade 8 U-bolts round out the rear details.

To finish up kit, a complete set of Rusty's Hydro shocks are included. These shocks provide excellent on- and off-road performance along with the proper length to work with this complete system.

The saying "Often Copied, Never Duplicated" certainly applies to Rusty's FSJ kits. 3-D computer modeling and extensive development and testing were all used to create a suspension that was second to none. This suspension offers a great on road ride, extra load capacity, and great articulation. Make sure you don't accept anything less than Rusty's!


  • Best Quality Parts Built
  • Great Ride & Articulation
  • Complete Kit
  • Limited Lifetime Warranty

• 2 - 3.5-4" Front Leaf Springs
• 2 - 3.5"-4" Rear Springs
• 8 - Grade 8 U-Bolts
• Brake line Extension Brackets
• 4 - Rusty's Hydro Shocks
• Complete Instructions

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