Hiya chotus- Is yours a Plunger/bolt-on semi unit, or Swing Arm ?
Either way there 'should' be a cutaway on bottom-est screw boss in the inside of the outer case, however; having said that, I have a spare Plunger outer case that doesn't have that (as per photo), but has a level screw cutaway just up to the left of the inspection/filler hole. (not sure which on a S/A model).
I added some oil to mine the other day and used some hydraulic oil, but only because I have it on hand and figured maybe no harm to see how it goes, given that ATF as normally used by many, and can also used as a hydraulic (jack) oil
- (but which grade of ATF ? ?
)
Rather than pull the level screw out, I added in 25ml increments, and had a look with an endoscope to see how high the tide was- but a small mirror with a bright light should work too...