Subframe/Diff Lockdown Kit 2002-2007 WRX and 2004-2007 STIPSP SUS 525 OVERVIEW Add drivetrain rigidity and precision to throttle input to your Subaru with our PERRIN Diff Lock Down System. PERRIN SUBFRAME LOCKDOWN The PERRIN Subframe Lockdown kit includes 2 urethane bushings, two metal sleeve washers and 2 bolts. They work together to solidify and lock the rear subframe in place, eliminating all driveline slop and that annoying thud from first to second gear. PERRIN DIFF LOCKDOWN The PERRIN Rear Diff