This isn't always true either. 4WD can mean that you send equal amounts of power to each axle, but at that point there are things that can change the amount of power going to each wheel within the center differential casing. If you have a limited slip differential (why some 4WD vehicles can drive perfectly fine on pavement) it'll basically send a 50/50 split (lock the axles together when going straight) but allow the axles to turn at different rates when making turns (otherwise bad things would happen). Some cheaper 4WD vehicles (and many 2WD vehicles) have open differentials. Open differentials send the power to the path of least resistance (bad for traction, and also why if you're in gravel the loose wheel usually just spins while the other one doesn't). There's also a fully locking differential that literally locks the axles no matter what. These cannot be used on pavement for obvious reasons (well, think about turning a corner, the outside wheel will have to turn faster than the inside wheel). AWD vehicles have a center diff typically and also often employ limited slip differentials (but sometimes again, they have open and/or auto-locking diffs...ARB made air locking diffs at one point, not sure if they still do) at each axle as well which enables a mechanical distribution of power. Some newer vehicles have replaced the axle differential gears with anti-lock breaking systems that provide resistance to open diffs to regulate wheel spin (artificially add resistance to the spinning wheel).....sorry, before I became a computer geek I built motors and off-roaded in my 81 CJ-5, after that I drag raced for fun on the weekends at the local track. I had a limited slip in the mustang I raced and a fully locking one in my Jeep. Jeeps (and older 4WD) are interesting b/c many come with what are called locking hubs ( https://en.wikipedia.org/wiki/Locking_hubs ) which are not all that common today. Even if you do find them, they're usually auto-engaging vs. the ones you have to get out an manually turn to engage the front drive shaft.