eating gear
When you're eating so much you're like a monster who just found a buffet and doesn't want to leave. You might even make a hand motion like you're changing gears on a car just to keep going.
I ate so much I turned into a monster and started making car noises.
That pizza was so good I did the gear shift thing and said 'I'm not done yet!'
I was eating like I was a monster and didn't want to leave the buffet.