Think about the speed of the ring gear, and how fast the spray from it can be at racing (or highway) speed. That's why a lot of differentials have a passageway cast into the carrier housing to lube the pinion bearings. Putting a 3/8" pipe threaded hole at a tangent to the ring gear allows a good bit of lube to be diverted through the cooler lines, especially at operating temperature when it thins out a bit.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!