Thanks to Bill for starting this thread it has been extreamly valuable.

Thanks to James for a detailed description

Regarding annular vs homokenetic ;

I ordered axles form a local parts house (Inaba in Riverside Ca. $59.95)
I got 2 different axles
One looked like the original
One had a collar with allen screws. It looked beefier. He said it looked like ones used in VW's and BMW's
Both had the same part number but were quite different. He asked if wanted one of each, since both should work the same. I replied "No thank you, it would look strange." I chose the beefy looking one instead of the OE looking one. I thought it looked more like a modern FWD. He had a replacement in a few hours.

Prior to the replacement, I had a loud clunk that I thought that I had traced to the U joint in the driveshaft. After the axle halves were replaced the clunk was gone. The play in the rear end is gone. I also replaced the center driveshaft carrier bearing and the two flex joints.

Prior to the axle and driveshaft service the transmission shifted poorly. It shifted OK if I was slow and carefull but unless I went slow, the gears would grind. I had changed the transmission lube to Redline MT90 a few weeks before. That had not made any change.

After the service, the trans shifts smoothly and perfectly. Go figure?

Posts on this site suggest Mobil One gear lube for the rear end. Racing shop near California Speedway where I got the Redline endorsed Mobile One, so I went for it.

BTW, the axles were shot. The boots were rotten. The flex disks were cracked, but the oil in the rear end was almost clear and smelled like steak and lobster with baked potato. OK not exactly like steak and lobster, but it did not smell bad like the stuff I would expect to find in a 25 year old rear end. It looked like it had been put in yesterday. There was no evidence that the rear end had been touched in years, if ever. Go figure?

BTW the drain plug is 14mm on my 1980 240D, and could not be found at Auto Zone.

__________________
69 220D not running
79 240D parts car
80 240D Beater runs everyday
81 300TD temp disabled cooling problem
82 300SD sweet