The Eibach Pro-Kit 6399.140 is a four-spring coil lowering set built on Eibach's progressive-rate spring design for the 2007-2008 Infiniti G35 X sedan with all-wheel drive. It is meant to lower the center of gravity and reduce body roll and nose-dive in everyday driving without the stiff ride of a track-oriented setup. Compared with a generic drop spring, it comes from a manufacturer that markets the kit as engineered and tested for street performance, and its progressive rate is intended to keep ride quality comfortable while improving cornering control. Buyers searching for 07-08 G35x AWD sedan lowering springs, progressive rate coil springs, or Eibach 6399.140 are looking for this exact application.
The manufacturer lists this kit only for the 2007-2008 G35 X sedan AWD, so it is not a fit for other body styles or drivetrains. Because it is a spring-only swap, the job centers on the front struts and rear coil assemblies rather than the whole suspension. Owners on user forums generally recommend a professional wheel alignment afterward, and some report that camber adjustment was not needed at a drop of this size. Check your wheel and tire clearance before ordering, especially if you run larger aftermarket wheels.
The manufacturer lists this kit for the 2007-2008 Infiniti G35 X sedan with AWD. It is not listed for other G35 body styles or rear-wheel-drive models, so confirm your exact trim and drivetrain before ordering.
Owners on user forums generally recommend a wheel alignment after installation. Some report that camber adjustment was not needed at this drop height, while others noted the settling that can occur over time.
The manufacturer publishes an installation instruction sheet for this part number, which is worth reviewing before you begin the job.
This is a moderate-difficulty job for an experienced home mechanic. Owners on user forums describe it as a floor-jack and socket-set job that requires a spring compressor and patience, since the strut and spring assembly is awkward to unbolt, lower, and realign. Work one corner at a time, use the jack to line up mounting holes, and keep the factory jack and stands handy. Expect the front to take the longest. Once everything is reassembled, torque all fasteners to the manufacturer's specification and schedule a wheel alignment.
