Symptoms of Bad Transmission Mountsby Quinn MarshallUpdated July 19, 2023
Transmission mounts are circular metal brackets that support the transmission and utilize rubber blocks to prevent the vehicle from vibrating and rattling while running. Most transmission mounts also come with rubber blocks or bricks, which sit between the chassis of the car and the mounting bracket to keep noise from being transmitted through the body of the vehicle.
A bad transmission mount can cause your vehicle to shake and rattle severely while accelerating. This is often caused by a broken transmission mount, but may result from worn or damaged rubber blocks. If the transmission mount breaks completely, the transmission may shift during acceleration, causing a knocking or clunking sound. If the transmission shifts and twists severely enough, it may damage other components, which cand result in additional noise and possibly damage.
When the rubber blocks between the vehicle’s chassis and the transmission mounts break free or become damaged, the vibration and noise from the transmission will be conducted through the transmission mount and into the chassis of the car. This is most often recognized as a roaring or vibrating sound that echoes throughout the vehicle during acceleration. If the sound is caused by bad rubber blocks, the transmission mounts may break, damaging the transmission.
Though rare, if a transmission mount becomes damaged and breaks, the transmission may become dislodged and fall from the vehicle. This will result in thousands of dollars in damage and is not easy to repair.
Video: How to diagnose a bad motor mount or transmission mount
Helpful comments on this video:
- Hey Chris. Thanks for all your great videos, I've learned a a ton from you and your tips are always handy! I have a slight problem with my engine. It's a 2006 Mercedes SLK 280 which are notorious for having a failing balance shaft sprocket but that part is already replaced but the engine still shakes on startup and Aldo when I pit it in drive and hold my foot on the brakes. It also had a slight shake before the balance shaft was replaced but it got worse after the replacement. Do you think that this could be due to worn out engine and transmission mounts? The whole engine was pulled for the balance shaft replacement so maybe the mounts now totally gave up on functioning properly? I would like to know what you think of it. Thanks for your time and answer and keep up the good work!
- Man, this is a great video! I just got a car (used) and when driving, I used to feel that weird shaking movement. First they told me those were caused by oil entering to the spark plugs... But then they said they were fine, it was just the motor and transmission mounts. Your video explains all. Great content!
Based in New England, Quinn Marshall began her writing career in 2004. She was a featured writer for Laptop Logic and contributes to publications such as "Smashing Magazine."