With the remote shifter design of the 911, the engine and transmission mounts are a considerable contributor to shifting precision. Old, soft, sloppy mounts lead to the transmission moving around and completely throwing off that coupler alignment you spent so much time making perfect.
With your hand lightly on the shift knob while driving your car at low speed, say 20mph, stab the throttle then quickly let off. Does the shifter lunge in your hand? If so, that indicates your mounts are in need of replacement.
The transmission mounts have the greatest impact on shifting, but the engine mounts also play a role.
Our mounts included aluminum housings to accept symmetrical cushion inserts. The symmetrical design allows the mount to be used effectively in both the engine and transmission positions (inverted).
3 durometers of urethane inserts are included and allow you to tune the response and hardness to match your application. Yellow are stiffer than factory but are very compliant as far as urethane goes. Red are a step up in hardness but still effective at damping vibration, and the black are a stiff urethane (but not as hard as nylon or plastic) for the highest level of control but increased noise transmitted through the mounts. Mix and match the inserts to fit your needs.
Mounts are sold in pairs. 2 pair needed for a full car set for both engine and transmission.
901 transmission mounts require pressing out the old rubber from the mounting crossmember.