Am I right in thinking that the hole in the rear of the primary chain case is just for filling and the smaller 5/16” hole in the bottom of the chain case is the oil level? On the Hitchcocks online parts book the larger plug at the rear is described as Drain/Filler plug. How can it be both? There are only two plugs in my 1955 chain case, the larger one at the rear and the smaller one at the bottom. Logic would suggest that the lower one is the drain plug but in the Hitchcocks parts book it is described as the level plug? I can’t find anything in the workshop manual
that describes how to fill the primary chain case to the correct level, or how much oil to put in there. Hitchcocks also state that they use and recommend ATF in the primary chain case. Does anyone have any advice on this please?