Always start with the cheap/obvious stuff.
check out your brakes to see if you have a warped rotor or severely worn pads. Make sure your parking brake is fully disengaged. Inspect your tires to look for wear. My guess is a bad tire. They can rumble like this.
The 8.8 is a good rear end. Unless you have a leak that went unattended or if the car was abused, it’s unlikely to be a rear gear or diff failure.
Without any details at all about the car, the conditions when it happens (other than driving slow), It’s really hard to say.