The best explanation of a differential is from 1937

The first time I saw this video, I was hooked because I’m natively a bike guy and it starts off with motorcycle stunt riding. But the guys horsing around on those ol’ Harley VLs actually are the producer’s interesting and educational way to visually demonstrate why a differential is necessary in any two-track vehicle. Here, take a look-see.

This video sucked me in beyond the bikes, though. Being a video guy—man, this production value is through the roof. Many camera angles, beautiful cutting, on-screen graphics—this is some pretty heady stuff. Heck, the Wizard of Oz didn’t even have its famous scene in color until 1939! I mean, they are literally using horse-drawn wagons that people at that time might have been more familiar with to illustrate the theory of operation. They even built a special vehicle interior to illustrate why low-pinion driveshafts came about.

The other reason I love this video (and you will, if you turn wrenches or sell parts for your daily bread) is that it is so good. Forget about the age of the vehicle; the explanation and illustration is easy to understand and it’s still totally relevant.

Sure, nowadays we have portal axles, LSDs, (and simulated LSDs by way of four-channel ABS), but if you started at this video, all those concepts are pretty easy to understand.

Enjoy it. And maybe invite the up-and-coming C-tech or your current lube bay jockey to take a peek, too—they’re likely the ones who will benefit most.