Torque converter chatter, I had this same problem on my 08 Limited. the fix for mine was to drain the transmission and converter. If you can let the converter drain over night. Install a new filter and refill. I did mine two months ago and it's been fine.
My name is Dave, I just bought an 02 after having owned a 96 Explorer for 8yrs. I've already used the info on the forums a few times for some minor problems, so I figured I join and say Hi and Thanks! :D