Same with my '07 XL Denali. I only see that kind of play on the front driveshaft because that's the shaft that's driven by the chain inside the transfer case. The rear driveshaft is direct-driven off the transmission output shaft, so any play in the rear differential isn't going to be felt by trying to turn the rear driveshaft. That's why I say it's important to get a stethoscope on that transfer case, so you can confirm that that's where the noise is coming from. Super common on higher mileage AWD GMT900 rigs, by the way.Here's my question... I do primarily hear it form the transfer case but I dont see that kind of movement from the rear driveshaft when doing the same thing, would the slack in the chain cause that?