When it's time to change the transmission and rear differential fluid, our drivetrain fluid kit makes it easy. You get enough Subaru Extra-S transmission fluid (3 one-quart bottles) for your gearbox, and a new drain plug gasket. The owner's manual specs out 4 litters of fluid but that is only if you are rebuilding the trans and its totally empty. We have found three to be the perfect number for regular service intervals.