1927 12/4 rear axle oil level

[wallis81+[]

How much oil should go in the rear axle? The handbook does not specify the correct level, simply saying inject a gun full every 2-3000 miles. I use a 250 grade gear oil up to just below the nipple. Is this also a level plug? I notice no oil is coming out of the holes at the outer ends of the axle so worry that the wheel bearings are being starved of lubricant.

[MSMulliner]

As far as I can gather the level has to be kept below the filler level plug by about 1/2" to 1" to prevent oil getting into the drums. The gearbox similarly should be about 1" below the level tap/plug. No capacity given for diff as it was originally filled with oil/grease mix!!