Swival pin housing

Hi all
Was going to change the oil in the swival pin housing I have a 1995 300tdi, according to the Haynes manual u fill up with 80-90 gear oil untill it comes out of the oil level hole after first draining the old oil. But on inspection there's only a filler plug and no drain plug or oil level plug so I guess it must be a one shot grease that goes in there , and if that's the case it must never need new grease unless u would have had to strip repair the housing??? Any help input would be gratefully appreciated

yes grease and it will need some more in time,it drifts into the diff oil and does leak out slowly ,if you remove filler and grease is obvious its ok if it isnt add half a oneshot sachet