I was doing a little more PM on the cruiser today and I unbolted the rear drive shaft and slid it apart. Cleaned the splines off, wiped out the female splines as much as possible and applied some Mobil 1 synthetic grease over the male and female splines. I put a shot of grease into the U joints and reassembled the rear shaft. I left the zirk fitting off as I pushed the shafts all the way together, put the zirk back in, and then extended the shaft to bolt up the rear U joint.
I also changed the rear diff oil, drained 3.5 Qt of tranny fluid and refilled and lubed the front drive shaft a little (without removing it though).
Went for a drive and the slight clunk I was becoming more aware of was gone.
I didn't really notice the clunk when I test drove the cruiser 3 weeks ago, but after a couple hundred miles I started to "sense" it. 
I was worried at first, but after reading through some old threads and doing this PM, I feel a lot better about the truck. 
Just thought I would pass on some more validation for the donk root cause....
I also changed the rear diff oil, drained 3.5 Qt of tranny fluid and refilled and lubed the front drive shaft a little (without removing it though).
Went for a drive and the slight clunk I was becoming more aware of was gone.
I didn't really notice the clunk when I test drove the cruiser 3 weeks ago, but after a couple hundred miles I started to "sense" it. I was worried at first, but after reading through some old threads and doing this PM, I feel a lot better about the truck. Just thought I would pass on some more validation for the donk root cause....
