2006 Ford Explorer drive train noise

I have my truck on 4 jacks and the wheels off. I started the truck and put it in drive. The left rear wheel was very noisy. I removed the caliper and rotor and the noise was greatly reduced. Parking brake maybe? The left rear and the right front rotate at the same speed. 4 wheel drive is off. The left front rotates in a jerky, on, off, clunky noisy motion. I was able to hold the right front rotor and the left side rotates ok. I think this is normal but it does the same in 4+4. I disconnected (electrically) the shifter solonoid and the front wheels stop turning. I"m not sure why the wheels stop.
The left rear shaft seams to have alot of play when turning it by hand. About inch and a half to two inch rotation. It clunks when it hits the end of rotation.
The oil levels and condition seams ok in the differentials.