97 4WD 5-speed

Started noticing a repetitive ticking/clicking at very low speeds, just before I stop. Seems to be coming from the middle or aft of the middle. Jacked up the rear end and no noise when spinning the rear wheels. But when I twist the rear driveshaft I get a sound that is very much like what I hear at slow speeds. It does not seem to be the u-joints, they seem tight. There is play at both ends of the shaft when I twist it, and the sound seems to be coming from the transfer case although there is a lesser sound at the rear diff. Is the play normal? Any idea on what it could be? Everything works as it should, including 4WD. I'm not 100 sure this is the same sound I'm hearing when its moving.

Haven't had time to check the gear oils yet.

When is the last time the propeller (drive) shafts were greased?

Late spring/early summer. But it doesn't seem like the noise is coming from the shaft itself, though I could be wrong and often am.

Just thinking that since turning the shaft reproduces the sound.

If the needle bearings in the u-joint caps start to go they'll make a clicking sound. You could put all four wheels on jacks, put it in drive and listen underneath while it idles to get a better idea.
If you still have an OEM driveshaft and a u-joint is shot in the double cardan, you're gonna want a new driveshaft from a driveline builder like Tom Woods as they're next to impossible to service. If it's at the pinion then you lucked out.

Actually the sound I reproduced seemed to be coming from the transfer case and/or rear diff just as they were engaged, and I wasn't rotating the shaft I was twisting it back and forth (it was in gear)