[Coggeshall]

Prepping to change all my fluids before hauling a trailer up & over the CO Rockies, but the instructions for the rear diff have me stumped. While the manual is very clear that oil should come up to the level of the filler opening for the Tcase & front final drive, all it gives for the M226 is this picture that suggests the oil should be an unspecified level below the filler plug. I'd rather not fill based just on what I replace because I have no idea if it's right to begin with.
What is a good rule of thumb to follow, or is there some sort of palpable/tactile fill line inside? I haven't put my finger into the greasy abyss myself, yet!

 

[Jard]

Fill it till it dribbles out the fill hole. It should be at the bottom of the fill hole, roughly, but a little over will not damage it.
It is just like filling an old ford, chevy, dodge, toyota, honda, mitsubishi, subaru, landrover, ac, bmw, mercedes, ect......

 

[prodragon4x]

Make sure you're on level ground, and make sure you remove the fill plug first before draining the old oil. Refill until oil starts to drip out the fill hole.