7 Things you should never do in an automatic transmission vehicle

1. Don’t shift from drive to reverse before the car stops moving--When you do this, you will damage the transmission and components because you are technically using the transmission itself, not the brakes.Consistently doing this will run you the risk of expensive damage.
2. Never put the car in park before stops completely-- If you put the car in park while it is still rolling, either the locking pin or the output shaft may break or become eroded.
3. Don’t put the car in neutral at stop lights--When in neutral, you don’t have much control over the vehicle. This means, if you must perform emergency action and you may not have time to execute the maneuver. If the light turns green and you forget you are in neutral, you will rev the engine, burning more fuel. We reccomend keeping your ignition on, the car in “drive”, and your foot on the brake whenever you’re stopped at a light.
4. Don’t coast in neutral--Contrary to popular belief, this does not save you gas. Again, being in neutral leaves you with less control over the vehicle—all you can do is slow down, you won’t be able to speed up if the need arises. Your car’s engine runs at its lowest RPM and the oil pump works the slowest when you are in neutral, therefore, the engine doesn’t cool down as well as it should and may fail due to friction and heat.
5. Never launch your car from a stand still--Launching your car is basically revving car while still in neutral and switching to drive to accelerate very fast from the stop position. This will cause serious harm to bands and clutches of the  transmission. If you continue to launch this way, these parts will not be able to hold friction anymore and the transmission will begin to slip when in gear.
6. Don’t keep the gas tank on low--Ignoring the gas light will cost you more than filling your tank up. To run properly, components of your car need proper fluid pressure. Keeping your gas tank at a reasonable level keeps different parts of the car lubricated. If you keep your car running on low fuel the lack of fluid will cause the parts to wear out faster than normal.
7. Don’t let water get in the transmission--When water infiltrates the transmission, it gets absorbed by the friction lining of the clutches.This causes the glue that connects the material and the clutch plates to dissolve. The water will cause rust to form on the metal parts of the transmission.

The most common course of action is to overhaul the transmission.