Noticed rear end noise while spinning rear wheels...normal?
 

I was starting a 4 wheel brake job today and jacked the rear end up. I usually don't jack both sides up at once, and I can't recall a time when I did and was able to spin the rear wheels, which is what brings me here. After banging around on the passenger side rear rotor, which was seized on, and stuck on the emergency brake shoes some how, I started spinning the wheel around the best that I could. With the E-brake shoes being stuck, it wouldn't turn much. Once the rotor broke free, and I started turning the hub, I could hear a very distinct clinking noise. It sounded a lot like mechanical gears turning, like a bicycle chain, which lead me to believe it may be a normal noise, due to the gears in the differential, but I did have a wheel lock up on me today (which is why I started the brake job, pad/rotor destroyed), and I hope that it was just related the the seized caliper and destroyed pads, and not the rear end.

Does any of this sound familiar? Is a distinct, repetitive clicking noise normal while spinning the rear wheels with the car jacked up?

I would check the fluid level, but it's probably okay. Whenever I've had a live axle off the ground with no wheels attached, you can hear and feel the teeth when you turn it. It's the nature of straight-cut gears to be noisy. The spider gears and their mates are all straight cut bevel gear, where the ring and pinion are helical and therefore quieter and smoother feeling. I would think that you are fine, but if you want to be sure, check the fluid level.