Engine mounts insulate and prevent engine vibrations from transferring to the passenger compartment. Weak and broken motor and transmission mounts are one of the most common causes of passenger compartment noise and vibration. The vibration is even worse on smaller front-wheel drive vehicles.
Engine mounts are made of rubbers capable of withstanding engine heat while insulating engine vibrations from the vehicle's frame.
They break on older vehicles from years of heat and stress. The vibration caused by worn or faulty engine and transmission mounts is passed onto the passenger compartment dash and steering wheel.
Check these mounts if excessive vibration is a problem. It's also a good idea to check the mounts after removing an engine or transmission. When they are old, they often break or become damaged during removal/installation.