When you `shovel something down’, you take a huge bite of something and gulp it down very quickly. It is an expression that is mostly used in informal contexts.
Listen, you don’t have to shovel your sandwich down. We have plenty of time.
When you `shovel something into something’, you make use of a shovel to put something into something else.
The old gardener spent a lot of time shovelling gravel into the wheelbarrow.