SuperPro 1990 Mazda Miata Base Rear Differential Mount Bushing KitThis kit replaces the forward differential mount bushings known as the pinion mount bushings. The OEM units are soft rubber and break down fairly quickly with that wear accelerated the harder they are used. The worn bushings allow more movement of the rear differential under changing loads. This can initially be felt behind the wheel as slower and sloppier responsiveness, and as the OEM bushings near the end of their life or fair it can be accompanied