Drive train clunky noise

[Gtpdz]

I noticed a metal rattling noise coming from the front when the car is under load with very little throttle( when the exhaust shakes most). Jack the drivers front wheel up and turn the wheel by hand, it has about 10-15 degrees of play and a clunky noise before it engage the viscous coupling. After the coupling is engaged there's no noise. Just wonder is this amount of play is normal?

 

[presterone]

Post a video, so you are watching the rear driveshaft while doing this? Is that what you mean by the coupling engaging?