The driver's car seat of my Mazda Demio vibrates when my foot in on the brake. 18$ h paid through paypal and still no answer
Hello and welcome to JustAnswer!
Based on your description I'm not sure that you need a transmission.
Does it vibrate only when pressing the brake coming to a stop? If it happens at any speed but only when pressing the brake then you have warped brake rotors.
Does it vibrate only when stopped and the transmission is in gear? Vibration from the powertrain will transmit through the body when you have a loose or broken motor mount.
Is it shuddering just at the end of the stop and dragging the engine down, much like a manual transmission if you forgot to push in the clutch? THis would be transmission related. If the torque converter clutch stuck on due to a solenoid or converter issue then it would cause this.