Mr. Rawles,
I have not seen the subject of a 2WD with a limited slip differential versus a 4WD addressed on your blog. If it has, I have missed it.
Most 4WD vehicles have “open” differentials and if one wheel on that axle spins, then the other stops. I have seen 4WD trucks spinning the driver side front wheel and the passenger side rear wheel and nothing from the other 2 wheels (dead stop). There are vehicles with limited slip front and rear but they are uncommon unless you special order them that way new or have aftermarket parts installed.
A limited slip differential will still transfer about 30% power to the non-spinning wheel thus giving you some traction. I had an old 1969 ford pickup when I was a teenager in the 1970’s and it had a limited slip rear end. Doing all the truely dumb things a teenager will do, I only got that thing stuck twice. Every other time I was able to get it unstuck on its own. Admittedly, the worst off roading I did with was cow pastures, fire break roads, and power line easements in Texas. (Gravel and dirt roads and mud.) I do not have much experience in snow, perhaps some other readers have info about it on this subject.
It is a LOT less expensive to purchase and maintain a 2wd limited slip differential than a 4WD setup and you get pretty close to the same traction capabilities in the real world unless you are seriously off roading or in snow. They also get better gas mileage.
4WD is better in extreme conditions, but day to day, pre-SHTF you are rather well served with 2WD and limited slip, depending on your climate and terrain.
Just my two cents worth, I have learned a lot here and want to contribute. – John in Texas
Mr. Rawles,
Several years ago I came across an article in a 4-wheel drive magazine (I can’t remember which one) where they tested a 2-wheel drive pickup versus a 4-wheel drive pickup. They concluded that a 2-wheel drive could go about 85% of the places that a 4-wheel drive could go if set up correctly with off roading tires, beefed up suspension and a winch. Since most 4-wheelers tend to add those features anyway, you’re still saving money because a 2-wheeler can be several thousand dollars cheaper than a 4-wheeler. Add to that the lower overall cost of operating it daily because of better mileage and no differential to wear out and a 2-wheeler is a viable option.
There were two caveats with the 85% percent number – Heavy rock crawling and serious mug bogging were definitely out. But then again they found that the person driving the 2-wheel drive truck tended to take a bit more care in picking their line because they didn’t have that feeling of invincibility that some get when driving a 4-wheel drive truck. – Matthew B.