What is the difference between a grav belt and chute?
Both are on the table in Suns of Fortune. But Grav belts are not described.

Also how would you put repulsors on a Droid Character?

The main difference is that the grav belt doesn't exist. It was removed from the book, but FFG forgot to delete the entry from the equipment list.

I'd give the droid repulsors, but limit its flight ceiling so it wouldn't be able to fly unrestricted. Or if it did, it would be something along the lines of having a jet pack permanently built in. Otherwise you're giving players a free run around the terrain rules, making talents like Swift worthless.

Grav belts aren't supposed to be in there, but if you wanted to incorporate them, just leave them the same as Grav Chute in terms of function, and treat it as a belt instead of a backpack.

I assume you mean repulsors for droids like ones without legs or wheels and get around by floating. In that case, I'd treat it like how Toydarians are with their Hoverer racial ability: "... hover slightly off the ground. When hovering, Toydarians do not have to spend additional maneuvers when navigating difficult terrain. Otherwise, their wings allow them no extra capabilities beyond those of a normal, walking character."

3 letters mostly.

Back in the old D6 days it was the Iyra gravity belt, basically the same kind of device as a grav-chute.

Pretty important for anyone who has a habit of being clumsy or falls off things