Along with the rear beam mount bushings, the differential mount is the most important bushing to upgrade on the car. Unfortunately, it is also the most overlooked bushing to replace. A weak differential mount causes a whole slew of issues that aren't necessarily transparent to the driver. First of all, the ride height of the car sags as the mount ages. Basically, the chassis, which pushes down on the differential mount and ends up sitting closer to the differential case and the beam, since the differential mount lacks compressive strength. Additionally, the weak rubber of the mount allows the subframe to move around, which causes the rear end of the car to feel squishy and slow to respond. This problem isn't limited to merely ruining the experience for the driver though. A subframe that moves with respect to the chassis creates significant toe changes that tremendously decrease handling grip and straight line grip. On a standard car (especially a high powered one), you can actually see the rear wheels move back and forth in the wheel well with your naked eye while the car is accelerating when a factory differential mount is installed. Besides the loss of grip and loss of driver confidence, the motion of the subframe also allows the rear tires to contact the wheel wells in hard corners when wider-than-stock wheels are fitted. By the way, ALL originally-installed differential mounts are weak regardless of mileage! It is R&B Motorsport's opinion that even brand new Ford differential mounts are too weak to use on high powered Cosworth that isn't being restored for just showing at bufty Concours d'Elegance.