With some NBU 30 PTM lubricant I got on Amazon, I decided to service the final drive splines. 

Years ago the previous owner was the last to ride this bike. I'm not sure if he or the owner before him had taken it somewhere for spline lubricant.

Anyway I opened it up and found brown stuff had been used. 





I don't suppose you can tell the quality of the splines from that mess? 

Whatever the brown stuff is, it's not supposed to be used here. Some of it in the spline teeth had a tar consistency that I could scrape off in peels. It seemed to have begun to separate by density. Some liquidy amber oil dropped out of the housing when I loosened it.

Here it is after some cleaning.



I didn't use a solvent but I've heard brake cleaner works well (??) I plan to return to it for a more thorough cleaning. 

Sorry! I forgot to get a clean pic before I put some moly on. You can see residual brown stuff mixed in. I'll probably wipe it off to do a better job later  What do you reckon about the amount?

That's way more lube than you need.  Most of it will be scraped off when you put the drive shaft back on. 

How many miles?  The splines are showing some wear. 

The brown stuff could be the factory lube.  30+ years old now.

What you want to see is a nice wide flat surface on the top of the spline. 

With the wear that appears on the drive shaft splines, I would take the time to do a very thorough cleaning of both the shaft and the final drive to remove all the metal particles that have been worn off before putting any new lube on them.  Those particles will act as a grinding abrasive and speed up the wear on what remains.

Geez I hope it's not original lube. My bike has almost 38000 miles. Great tips thanks

I have a shop record for "lube rear splines" done at 16912 miles.
And another for "remove install trans lube spline" done at 34496 miles

Doesn't look like factory spline lube to me. The factory stuff looks "drier" (not as oily/reflective.) The color kind of looks like rust, only redder.

lol , what you have applied is enough to do both ends of 3 or 4 maybe more splines . you are supposed to apply thinly with a small paint brush . i guess it wont do any harm

Right, here are newer photos I forgot to post: I re-cleaned the splines and applied less lube. Does it look reasonable?

taube, that's still more than enough

your splines already show considerable wear - the brown stuff is most probably the result of tribo-corrosion (fretting corrosion)

BMW does recommend the use of Staburags
https://www.motofab.com/data/pdf/staburags_nbu_30_ptm.pdf

different owners in a German forum ('flyingbrick') recommend lubing of the splines once a year

Once a year has been my routine, and even my RT with 100K shows zero signs of spline wear.