Taking any remotely interesting mechanical contraption and replacing one of its covers with a transparent one almost always yields deeply satisfying visuals. And that’s the case here with this Ford F-150's clear rear differential cover, which shows gear oil splashing around the bearings and gears.
I won’t pretend to be an expert on differentials, but what I do know is that they’re basically cases filled with bearings and bevel gears, whose torque-transfer efficiency and overall longevity is improved via splash lubrication. As the gears (particularly the ring gear) spin, they pick up the 75W-90 (or whatever weight gear oil you’ve got in there), and splash it all over the place to make sure the gear teeth don’t actually contact one another, but are instead separated by a thin film of lubricant. And also to make sure the rollers in the bearings don’t contact and chew up their races.
Of course “splash it all over the place” makes it seem like this lubrication method is arbitrary, when in reality, quite a bit of engineering goes into ensuring that oil gets deposited to the parts that need it. And seeing that strategic splashing through a differential is deeply, deeply satisfying, as you’ll find out when you watch this YouTube video by diesel performance outfit Banks Power.
Oh yes, just look at that ring gear grab that oil and precisely splash it onto the spider gears and pinion bearing. And check out how the oil level increases due to aeration (that’s not good for lubrication or for oil oxidation)—and this is with anti-foaming agents in the oil!
This is all part of a multi-part series in which Gale Banks is trying to determine whether aftermarket differential covers—common modifications among pickup truck folks—are actually worth a darn. You can check out the other videos on his YouTube channel.
Or you can just watch this video on loop, and enjoy the satisfaction of that stock-shaped diff cover precisely distributing lube in that rear end.