###You should check the rules on Dragging.
While you could still grapple such a creature, you would also have the option of dragging it.  Your choice depending on which rule you want to use.  I would use dragging myself.

As per the ***PHB p176***:

> ###Push, Drag, or Lift.
> You can push, drag, or lift a ***weight*** in pounds up to twice your carrying capacity (or 30 times your Strength score). While pushing or dragging weight in excess o f your carrying capacity, your speed drops to 5 feet.

*emphasis added to the word **weight** to show that you can drag creatures (who are not resisting) or objects*