What’s the Diff?
Ask 10 people what the most important part of our sport is, and you’ll probably get 12 different answers. The answers will range from tires to trees and everything in between. But the fact of the matter is that it all relates down to gears. Yes, the lowly gear, not big engines or massive tires or shiny paint. In one form or another, without gearing our sport wouldn’t exist in the way it does today. We could do without tires, and we could do without trees, but gearing is what binds our rigs to the dirt, and to our very souls.
You may think I’m off my rocker on this, but gears are what hold it all together. From the simplest gear, which is a key (lever) turning a tumbler in the dash, to the final differential gears that transmit power out to your tires, gears rule the world. That may be why I am obsessed with gearing in 4x4s, and why we devoted a major portion of this issue to it.
While we have bypassed a major gear subject in this issue of transmissions and transfer cases, the axles are historically known as third members because they are typically the third member of a vehicle’s powertrain after the engine and transmission. Of course, in a 4x4 we screw up this nomenclature by sticking a transfer case in between the axle and tranny, as well as throwing a front axle into the equation. That should then be known as a fifth member, but as members of the Fourth Estate we’ll bypass that thought for now.
Of all the unique and interesting gearing devices on our rides, the axle differential reigns supreme. It can be used to its designed advantage, modified to an extent where it is barely recognizable to its earliest designers, and even completely eliminated in an automatic design, or a selectable version as well. But then is the differential still that? To be a differential, the machine needs to differentiate the power to the two axleshafts; a welded unit is no longer a differential because it doesn’t differentiate. Luckily for us we’ll simply call it a welded diff, a Lincoln locker, or a spool. Because really, what’s the diff?
To that end we give you a photo in this column of a unique machine. If you are the first to correctly identify and explain its function, you will receive a shiny new set of 4-Wheel & Off-Road license plates for your 4x4. Care to give it a try? Send us a note at email@example.com.