True ’wheelers believe that every OE system can be upgraded. However, some factory design quirks aren’t blatantly obvious. One example is Jeep TJ/LJ rear springs. Even die-hard TJ owners might not realize that their rear coils are mounted off-kilter.
The Slinky was designed to work on its side, but automotive coil springs aren’t meant to walk down stairs (alone or in pairs…). Coils that don’t operate vertically lose spring rate and ride height. Off-road traction suffers: during compression, the canted-forward rear springs push their axle progressively farther backward as the vehicle squats. Weight transfers rearward. This can be a problem during hillclimbs when the front end lifts as the rear axle attempts to slide out from under the Jeep.
Chrysler likely had a logical explanation for angling the TJ’s rear coil mounts — maybe it allowed the same-rate spring to be used for both hard- and soft-top vehicles. A straightforward fix is now available from Black Diamond, the suspension line that Superlift bought from Warn a few years ago. Called the TJ Coil Correction Kit, it consists of new upper frame brackets and coil seats that permit the top of the rear springs to be mounted farther back. The upgrade works with any brand of lift kit that has OE-diameter TJ rear coils.
Installation can be done by anyone who can competently weld and cut. The job is good old-fashioned R&R. For TJs that don’t have a body lift, Superlift recommends unbolting the rear body mounts and jacking the tub off the frame for an extra margin of error.
Mall-crawler TJs don’t need a rear coil correction. However, Jeepers who actually use their TJs or Unlimiteds on something other than flat ground and speed bumps will feel the advantage of better-controlled weight transfer achieved by the Black Diamond coil-correction kit.