Here's what the inside of a working differential looks like

Take a peek into the inner workings of a differential.

2y ago


I'll be honest I don't know exactly how differentials work. I understand that they distribute power between wheels and can vary that power input based on driver inputs and the general positioning of the car. Luckily today we get a peek into an actual differential working.


This video by legendary diesel truck tuner Gail Banks explores the interesting world of truck differentials. This test shows exactly what happens inside the casing by using a see-through part.

The most interesting bit of this test is how the differential lubricates itself at speed. I understand that the differential is a metal case full of gears and sometimes clutches filled with differential fluid. I assumed the gear oil arbitrarily flew around the differential case and somehow fell on the gears, but that's not the case.

In watching this video we get an incredible view of how the thick gear oil evenly distributes on the gears and forms a sort of wave around them. Hardly any of the gear oil flies around the case and instead falls exactly where it needs to. Damn those engineers are smart.

What other clear car parts would you like to see in action?

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Comments (24)

  • The result of years of trial and error, the study of fluid dynamics provides clues to the understanding of many instances of relative efficiencies. The capacity to maintain lubrication is dependant on the limitations caused by cavitation, turbulence, overheating. The heat dissipation requirement is something that is of importance in sunny Australia. I've seen many small cars cook themselves, whereas medium sized cars like the Ford Taurus and V6 Holden Commodore with larger components I guess have a better capacity to dissipate heat. It makes me think I should drive more slowly, ( road impact causes shock absorber fluids and wheel bearing grease to overheat and lose effectiveness ) and use a car with a larger grill and radiator. And remember , excessive heat has a detrimental effect on electrical flow - hot wires have higher resistance, and so spark plug leads are less efficient if your engine bay is really hot. I sometimes think that in Australia , mostly we should try to only drive at night, because of the detrimental effect of solar radiation on the cars electrical system. ( It is thought that cars use less fuel at night , partially because the cooler air is more dense, and so the engine takes in more oxygen, for no extra effort. ) For further reading on the relationship between electrical flow and temperature, I'd recommend the Oxford Dictionary of Physics. Keep cool and calm I guess ?

      2 years ago
  • Can't stop watching!!

    Shared to the D_TRB USA facebook page Chris!

      2 years ago
  • If you really want to understand how differentials work watch this video

      2 years ago
  • Peek, not peak

      2 years ago
  • Thanks for sharing this video. Learned a lot!

      2 years ago


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