This only happens when we put it into park and when we unlock it. I'm assuming it has something to do with the locks, but I'm struggling with finding advice! Please help!!!
power lock inside tailgate/hatch-door(s)? you can test that by removing power lock relay.
also are you sure it is not the rear/in-tank fuel pump? they can be quite loud.
Answers
Have you ever had anyone sit in the back tailgate area and try to locate the noise?
It sounds like it's at the bottom of the lift gate. Does that help?
power lock inside tailgate/hatch-door(s)? you can test that by removing power lock relay.
also are you sure it is not the rear/in-tank fuel pump? they can be quite loud.