A vehicle's transmission mount secures the transmission into place, preventing it from moving or dropping while the vehicle is moving.
The transmission mount has brackets that hold the transmission to the vehicle. The brackets may appear rusted or loose. This can cause the transmission to slip out of place.
There are bolts on the mount that aid in securing the transmission. If bolts are loose or missing, the transmission is not secure.
You may hear rattling sounds from the engine whenever you shift gears or accelerate. This indicates that the transmission is rocking or moving around because it is not properly secured.
Your vehicle may vibrate or shake when it is idle. This may increase or decrease when you step on the accelerator.