Here’s a good take on five things you should never do to an automatic transmission. It’s important to understand both, what you shouldn’t be doing, and why. Never put the vehicle in neutral when coasting down a hill. Not only does it prevent gas from reaching the engine, but you lose some control over the vehicle when it’s in neutral. You can’t seed up, and you only have the ability to slow down.
Another huge reason is that coasting downhill in neutral is illegal in some states. There are 15 states at present where it’s illegal. Always come to a full stop when switching from drive to reverse etc. Otherwise, you could strip your transmission’s gears. You transmission isn’t designed to operate as brakes. Its purpose is to help the motorist shift gears. If you’re a budding mechanic, this could all seem technical. Take it slow. There’s a lot of good information here.