Differential

How Differential Gear Works

Watch Video  Source: ConceptVBS

How to Change Rear Differential Fluid (Detailed Version)

Watch Video  Source: ChrisFix

How to Replace a Front Wheel Drive Axle

Watch Video  Source: EricTheCarGuy

Symptoms of Bad or Failing Differential / Gear Oil

https://www.yourmechanic.com/article/symptoms-of-bad-or-failing-differential-gear-oil
If your car has exceeded its gear oil service interval, or if you hear the differential whining, you may need to replace the differential/gear oil.

Differential: Operation, Functions, Parts

http://www.learnengineering.org/2014/05/working-of-differential.html
Learn topics in mechanical, electrical and civil engineering through interactive video lessons!

How to Care For Your Car’s Differential

http://www.popularmechanics.com/cars/how-to/g1140/how-to-care-for-your-cars-differential/
You change your engine oil every few thousand miles, but have you ever looked at your differential?