Project 2006 Infiniti G35

Having significantly improved our '06 Infiniti G35 Coupe's handling, braking and power delivery, the factory viscous limited slip differential's torque transferring ability has been increasingly exposed as a weak point during track testing. For the street, this type of differential is unobtrusive and relatively effective, but at the racetrack it quickly overheats and loses its ability to transfer torque to the wheel with the most available traction. Simply put, the factory VLSD isn't up to the task of converting available horsepower into forward motion when repeatedly dropping the hammer while exiting corner after corner around a racing circuit.

To address this weakness and allow our normally aspirated RevUp VQ35 to make the most of its 260 whp, we contacted our friend Yasu Fukui at Performance Partners Inc. PPi is an authorized U.S. dealer for ATS (Active Traction Service), a highly reputable Japanese manufacturer of clutch-type limited slip differentials, clutches, final drives and transmission gearsets. Because our G35 is a daily driver, we were wary of using a clutch-type LSD because they tend to be quite noisy, especially when making slow, tight turns. The chattering noise and jerking motion that results from the aggressive cam angle and binding of the clutch plates isn't an issue for a race car given the highly responsive torque transferring ability of this type of differential, but for a street machine it can be more than a little embarrassing pulling into a parking spot with the rear end of the car chattering and hopping around.

To address the noise and smoothness issues of a clutch-type differential, ATS has developed what it calls the Super Silent LSD. This is still a metal clutch-type differential and therefore retains much of the inherent goodness of this approach to torque transfer, but by reducing the cam angle and redesigning the clutch pack for a quieter, smoother and more gradual engagement, the streetability of ATS's new Super Silent LSD is arguably on par with far less aggressive types of LSDs, including viscous and gear-type (torsen or helical). For a more detailed discussion of how ATS developed the Super Silent LSD, visit http://www.ppi-ats.com/LSD/Silent_LSD_tech.html.

To make the installation a little easier, we picked up a used pumpkin from a wrecker so that we could build it with the Super Silent LSD while still driving the G35 to/from Auto Analyser Racing, where Andrew handled the install for us. After draining the diff fluid and removing the cover, Andrew measured total preload, ring gear to drive pinion backlash and ring gear runout and then measured these again after installing the ATS LSD so that we could ensure the new diff was installed in the same position as the OE unit and within the factory tolerances and specifications. After carefully marking all fasteners, bearing caps and shims, the roller bearings were pressed off the factory diff and onto the ATS diff and the ring gear was then transferred over and torqued to spec using an SPX OTC Angle Meter. After bolting the ATS LSD into place within the diff housing, a Nismo finned differential cover-supplied by www.mynismo.com-was then sealed and bolted up before filling the freshly built pumpkin with break-in fluid. The Nismo cover not only increases fluid capacity, the fins provide increased surface area for greater cooling, both features that should allow the ATS LSD to function optimally while prolonging the life of the diff fluid and the differential itself. What we didn't expect was the clearance problem the Nismo diff cover had with the Rear Active Steering assembly on our '06 Sports Package coupe, but with some careful application of a die grinder enough material was removed from the cooling fins to allow our freshly assembled pumpkin to bolt into place.