Baseline 4x4 Outfitters Newsletter

Shackle Reversal System Pros and Cons

Published 11/17/07
The shackle reversal systems are designed to improve the overall driving characteristics of the Jeeps and Samurais with leaf springs on the front axle. By moving the front leaf spring shackle to the rear of the spring, will greatly improve the overall driving characteristics of these vehicles. The military version of the Jeep CJ, the M38A1, was designed with the shackle mounted to the rear. Not sure what the intentions of the engineers were but this modification is limited only to that particular military version of the Jeep family.

The theory behind the shackle reversal system is to transfer the energy of varying road conditions to the rear of the Jeep creating a smoother ride for the passengers. In order to explain this, it is critical to understand how an axle works on leaf springs.

There are essentially 2 different types of leaf springs, flat and arched. The CJ family of Jeeps uses the arched type of spring. As the vehicle is driven down the road and a bump is encountered, the axle moves forward as the spring is deflected. The larger the bump, the more the deflection of the spring and the more forward movement of the axle. This is because the rear of the spring is mounted solid to the frame. This forward movement, allows the energy from the deflection of the spring to be transferred to the front of the vehicle and therefore has to be absorbed by the entire vehicle before it can be dissipated. With a shackle reversal system, the fixed end of the spring is mounted to the front of the vehicle while the rear of the spring is flexible through the shackle. As the springs are deflected, from road conditions, the axle actually moves towards the back of the Jeep. This condition creates a much more desirable driving condition for the occupants of the vehicle.

The YJ family of Jeeps uses a spring that is relatively flat in its design. The flat spring, as it is deflected, will cause the axle to move backwards. With this condition already built into the design of the vehicle, there will be little improvement noticed with the shackle reversal system. The greatest advantages will be noticed when the flat springs are replaced with arched springs that are designed to add additional lift to the stock height of the vehicle.

The shackle reversal system will help reduce the affects of bump steering but is more susceptible to the affects of nose-diving under hard braking applications. Overall we have found that the positive conditions created by the installation of a shackle reversal system, creates a more pleasurable driving experience for the occupants of the vehicle both on and off the road.