I can't find in any manual which plug is the fill level plug!
I have 3 to choose from.
2 can be removed with a 3/8 drive ratchet and one would need a, guessing, 5/8 or 7/8 wrench.
One of the 3/8 plugs has an "F" stamped on the housing.
Help please!

 

The one with the hex head should be for a temp sensor, assuming it's an Eaton rear end.
The fill level will be somewhat above the bottom of the axle tubes as the oil needs to flow out to the bearings.

 

Well that figures.... After searching all day for this info and giving up, then asking here, I found the answer!
So for anybody needing this info.
Eaton 2 speed differential 16244 series 16
Spicer housing (rectangular arm)
33 pints
Or
Vendor housing (round arm)
24 pints.

 

That must be a big diff to hold 33 pints!