AWD Chatter on hard turns 2002 Explorer

When turning hard right and accelerating there is a chatter similar to turning when in 4 wheel drive. The selector is in Auto when this occurs. It is intermitment and occurs more ofter when the car is warm but never severe only a slight chatter.

Is this likely an issue in the transfer gears/clutch or is it a sensor issue so that the AWD is being activated? Had a service shop check it today and they couldn't find an issue although they did notice the failure when test driving.

2002 Explorer Limited 94000 miles V8 4.6?