A transmission mount is a device that connects the metal housing of your vehicle’s transmission to the vehicle’s frame, subframe, or engine cradle. Not only does the mount hold the transmission in place, but it also isolates the rest of your vehicle from engine and drivetrain vibrations.
This is done by incorporating a thick layer of rubber (sometimes including a fluid-filled chamber) between metal brackets on either end. One bracket is bolted to the transmission; the other is bolted to the body or frame. The rubber section is sandwiched in the middle. Such an arrangement allows the transmission to move slightly when responding to various driving conditions without transferring vibrations to the occupants inside the passenger compartment. This makes for a smoother and quieter ride experience. Some transmissions will have multiple mounts.
Replacing a transmission mount generally requires that your vehicle be safely lifted and supported for access. The transmission must also be supported with a transmission service jack or special brace in order to relieve weight from the mount.
With the transmission’s weight off of the bad component, the mount is unbolted, removed from its location, and replaced with a new part. The bolts are torqued to specifications, the jack is removed, and the vehicle is lowered to the ground. Finally, the technician will likely test drive your vehicle to verify the repair.