yeah it could the a motor mount or trans mount.  if you cant visually see that the rubber is torn or separtated then get under there with a pry bar and pry up on the trans and see how much movement you get.  sometimes you cant see the rubber has separted from the metal untill it is pried up, same thing on the motor mounts.  that main HUGE nut on the transmount doesn't actually hold the mount to the crossmember that is just the solid connection for when the rubber does go out the mount isn't completely separated it will still have that big nut that keeps the tranny attached to the botton piece of the mount,  its a safety thing.