What’s The Diff? The Debate On 2WD Versus 4WD

Long before four-wheel-drive became the standard mark of what it meant to journey across the Earth’s most forbidding locations, the automobile was a machine that derived its motion from two spinning circles in the rear. Time, technology, and demand eventually made four-wheel-drive the trend to follow as manufacturers like Willys produced the CJ-2A in 1945, the first full-production four-wheel-drive vehicle for sale in the general marketplace.

But two-wheel-drive never went away. Instead, it became the standard operating procedure in a manufacturer’s lineup, from cars to vans to trucks to SUVs. Consumers had more options to choose from as the years went by, and when combined with increasing urban and suburban migration, consequently fewer and fewer found a good reason to have a vehicle that threw power to all four tires.

Off-roaders, however, had a lot to consider when presented with the options checklist. Four-wheel-drive offered peace of mind and security in times of duress, but two-wheel-drive cost thousands less and came with fewer concerns by virtue of fewer parts. And when equipped with a locking differential, aired-down tires, and sure-footed technique, a two-wheel-drive truck had a great deal of capability that almost put it on par with its four-wheeling brothers and sisters.

So the question becomes: just what can a two-wheel-drive vehicle accomplish? We picked the minds of enthusiasts, aftermarket figures, and racers to argue in defense of two-wheel-drive, and here’s what we found.

Popular Vote

Social news site Reddit was our primary source of gauging off-roading public opinion for the purposes of this article. We talked to three subreddits–/r/4×4, /r/2WDtrucks, and /r/trucks–to get a varied mix and see what sorts of ideas and commentary were out there. Here’s what people had to say.

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davidmichaelmalloy, /r/trucks: Beyond the improved fuel efficiency, 2WD trucks can be a lot of fun to drive! If handled properly, they can be used to navigate terrain that would make a 4WD truck struggle.

deerhurst, /r/4×4: I look at it this way. I use 2WD until I’m stuck and then lock it in 4WD and figure it’s probably time to go back.

I_Know_KungFu, /r/trucks: I think where you live plays a big factor…I’ve personally found that a good set of A/Ts or M/Ts can make a world of difference. 4WD is nice but it’s not a necessity for me, personally. Sure, there’s times when I’ve needed it and didn’t have it, but I couldn’t justify the extra $3,500 when I bought my last truck. Experience in adverse driving conditions are a big factor too, I think. I also think 4WD gives a lot of novice drivers a false sense of security. Having said all that, my next truck will be 4WD mainly because I’ll be able to afford it and it is a part of the truck that doesn’t depreciate as much as everything else.

mynameisalso, /r/trucks: It is a real [pain] to own a 2WD in a place where you get snow. I’d never own another.

4x4AZ, /r/trucks: 4WD is inherently better off road. 2WD can get you pretty far, but I wouldn’t ever want one for hard off-road stuff. The only advantage I can think of for 2WD is slightly better fuel economy and less weight. Not worth it [in my opinion].

MrCance, /r/2WDtrucks: My truck looks like a 4×4, but it’s 2WD…Whenever I’ve gone off-road, the truck does a fine job. It had some mechanical issues, but that was just because it’s old. As far as keeping up with the 4x4s, I think it stands up pretty well. I love my truck and I’ve considered doing a conversion, but I don’t have a big enough wallet for that. I’m constantly ridiculed by 4×4 people but this truck was my only option. Some day I will have a 4×4 something (preferably a Dodge Cummins), but for now, my 2WD Dodge Ram gets me from A to B.

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layer4andbelow, /r/trucks: I think the need for 4×4 is often blown out of proportion. A little skill and some light use of the pedal can get yourself out of most problems in 2WD. Almost every time someone is ‘stuck’ with a 2WD truck, it is because of two things: 1. lack of weight in the bed. 2. They mash the go pedal and expect it to not spin.

sn44, /r/4×4: As with anything automotive, it boils down to the driver and their skill set. I’ve wheeled with guys in 2WD that are great and blew my mind with that they could do. I’ve also wheeled with idiots in $50,000 custom 4x4s who still managed to get stuck on a tree stump. A lot can be said for preparation…when 2WD sucks is when time is a factor. Personally, I hate waiting around all day while some guy in 2WD has to winch himself through something easy that I just walked my rig though.

Professional: Industry Types

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Not all 4x4s and 2x4s are equipped point-for-point, but there are similarities in what each can be upgraded with to better their off-road performance. Chiefly, these options include locking differentials and tires. We asked a number of aftermarket specialists to weigh in on the topic, from Eaton Performance to Toyo Tires. Below are the questions we asked each of these companies.

The Eaton E-Locker.

The Eaton E-Locker.

Off Road Xtreme: How are lockers beneficial to 2WD folks?

Eaton, Michael Mulholland: A guy with a 4WD and no locker has less capability than a guy with a 2WD and locker. Three of our top choices for off-roaders are the E-Locker, Detroit Locker, and TrueTrac.

First is the E-Locker. It’s a selectable locker, being push-button, 12-volt, and electronically activated. It’s essentially an open differential on the highway, and has no effect on the driving. Off-road, it’s still typically unlocked, and it’s primarily acitvated for off-camber situations. Users can engage it and it locks the axle up. Push the button, and it unlocks. Great for the rear or front axle.

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The Eaton Detroit Locker.

Second is the Detroit Locker. Very strong, durable. It’s locked all the time and opens up in turns. It’s all mechanically activated based on wheel speed differences. Going around corners, you’ll hear clicking and clunking, but it’s unlocking to prevent wheel hop. It’s a great unit.

Then there’s the TrueTrac. It’s a helical gear. It adds some stability to the vehicle like a limited slip, but it has a 3.5:1 bias; if it has one tire in the air, it doesn’t work. But it does work to give positive feedback for when driving in the rain or snow. Off road, it’ll do the same thing and push the torque back and forth, or split it 50/50. On the road, it will be enhancing the vehicle’s traction. It’d be the option I go for on a vehicle like you’re describing. It also works great for towing.

The Eaton TrueTrac.

The Eaton TrueTrac.

ORX: How far could a guy with a locking differential get using something like a Detroit Locker or E-Locker?

Eaton, Michael Mullholland: Yeah, I don’t think anyone should be going off-road without a locker. Even a 4×4 with open diffs is really pushing its luck. It kind of depends on the right tool for the right job. In terms of off-road capability, the Detroit Locker and ELocker will be more capable, but you’ll have to live with it. The TrueTrac will work for a daily driver a lot better. At some point, going off-road is not the differential’s issue, but becomes an issue of suspension or tires. There’s probably not one thing you can do to change a vehicle’s capability quite like adding a locking differential; it will definitely enhance the performance of a vehicle. For mud, snow, and dirt, lockers make the difference, and it should be among the first things that a guy should do to get ready.

The ARB Air Locker.

The ARB Air Locker.

ORX: What is a guy missing out on if all he has is a 2WD with an open differential?

ARB, Matt Glass: A lot of traction. Getting into an off-road situation, he would only have one-wheel drive. It would extremely limit that vehicle’s ability to overcome obstacles. By using an ARB locker, he would have the selectability of on-demand traction by being able to engage and disengage at will. An air locker would give him true traction at both wheels. A wheel that would have otherwise been stationary would now have traction.

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A cutaway view of the ARB Air Locker.

ORX: How does an air locker work?

ARB, Matt Glass: The air locker replaces the factory open diff. The air is delivered at the push of a button into the axle housing and into the differential and actuates a clutch gear, it slides over a spline side gear, that spline side gear can no longer spin since it’s locked, and then the other internal pinion gears can’t turn either, and it essentially removes the ability of the axle to lose traction and you gain positive power to both axle shafts.

And the internals of an air locker look like a stock open diff. We have three internal pinion gears where most have two. The clutch gear slides over and covers the teeth that are on the case and on the side gear, essentially the side gear and case gear become locked together.

It’s instantaneous since the system operates on 150 psi. It can also disengage just as quickly. It operates independent of the speed of the vehicle, so a vehicle can flick it on at high-speed, it doesn’t have to be at 5mph or less like an E-locker. It’s just like an OE differential, you won’t notice any ratcheting or growl or sideways hop on wet pavement.

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The Toyo Open Country M/T tire.

ORX: If a guy only has 2WD and an open differential on his rig, what sort of tires would you recommend for stock wheels? (i.e. 31×10.5R15, sidewall considerations, etc.)

Toyo Tires, Jay Jones: We have a couple of options that cater to the off-road market, both from the Open Country line. These tires are the A/T II and M/T.

The Toyo Open Country A/T II tire.

The Toyo Open Country A/T II tire.

The Open Country A/T II is a good all-around tire. It has sidewall protection, and it’s better in the snow thanks to its built-in siping. It’s a versatile tire, good for year-round weather. That product is now OE on Ford King Ranch trucks. The new RAM Rebel will have the tire OE too, and they’re molding the center of the seats into the inserts, so sitting down in the seat will feel like sitting on the tread of the Open Country A/T II. They just unveiled it, and some reports say its like getting a back massage on top of being an aesthetic choice. Pretty unique. The A/T II is great for 90 percent highway, 10 percent off road.

The Open Country M/T is a step up in terms of aggression, so it’s a little louder, but it’s ready for dirt and sand and digging in. It has hook-shaped blocks in the center of the tread that will bite into the ground. The tread going around the lower sidewall of the tire is good for deep sand. That really helps with the traction, and it has quite a history with competition. It’s been in rock-crawling, DAKAR with Robby Gordon, desert racing, et cetera. It’s a good product in terms of durability, and that’s the stamp of a Toyo product. They’re consistent thanks to the multi-cavity mold, and use very little wheel weights to balance. The majority of our tires, including the M/T and A/T II are made here in Georgia. The A/T surpasses OE standards on radial runout.

Professional: Racers

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But it’s not just enthusiasts and company reps who have the full scope of what 2WD is all about. The realm of off-road racing also has its fair share of participants, most notably in the Lucas Oil Off Road Racing Series Pro 2 class, as well as desert racers like Class 8 competitor Dean Schlingmann (who recently took home the class win at the SNORE Battle at Primm). We took in their beliefs and arguments and compiled them below.

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Dean Schlingmann lets loose near Barstow, California.

Dean Schlingmann, Class 8 racer: The fewer moving parts, the better. Every part that moves has the potential to break. So, with 4WD, the likelihood of issues is higher than with 2WD. On the flipside, I run a full-size truck on 35-inch tires where others run on 37 or 39-inch tires. And since my truck’s weight is pretty high, I have to pick good lines wherever I can in the desert, where I’ll run into deep sand or silt.

From a fabricating standpoint, 2WD is significantly easier to plan for and modify than 4WD. If you go to a race, you will see 90-plus percent are all 2WD. We can’t break in a race, because it will kill us in terms of time; and there’s very little breathing room in that regard.

My rearend is a four-inch chromoly housing built by GMR, with a Currie 9+ third member, Sway-A-Way 40-spline axles, and the driveshaft is from a local place in Azusa. The front end is a traditional I-beam front end for a Ford F-150.

Carl Renezeder, Pro 2 racerYes, racing with 2WD did give me an edge when I decided to also race 4WD. 2WD requires a little more finesse to drive because you don’t have the front wheels to get you out of a sticky situation if needed. The biggest challenge with Pro 2 would is the truck setup for the track we are racing, and picking the right line to maintain as much momentum as possible without making contact with the other racers. Being packed in so tightly can get you in trouble real fast if you’re not on top of your game.

While I can’t get into the specifics on my truck, I can say that my team works hard to make sure that the truck setup will meet the challenges of the track that we are racing on.  We have amazing sponsors that work with the team to innovate and make sure our trucks are at their best to compete and win races.

In Conclusion

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So it seems that the debate between 2WD and 4WD rages on: 2WD carries with it the advantages of cheaper cost and lesser complexity, yet 4WD counts as a trustworthy option for scenarios where weather and terrain degradation are taken into consideration. But 2WD still has merits as a viable off-road drivetrain, and can reach near as great a length as its 4WD counterparts in the right hands.

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Across the entire spectrum of off-roading people, the consensus seems to be that all the tools and tricks can’t measure up to that innate human quality–common sense. Planning ahead, picking good lines, and always having backup are the keys to overcoming just about any obstacle that comes your way. Outside of that, a dose of good luck can’t hurt either.

So when the time comes for you to start again with a new rig, commit to due diligence and don’t let yourself down on research and reasoning. It’ll make the difference between making it home in time for dinner, or walking mile after mile in search of rescue.

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Article Sources

About the author

David Chick

David Chick comes to us ready for adventure. With passions that span clean and fast Corvettes all the way to down and dirty off-road vehicles (just ask him about his dream Jurassic Park Explorer), David's eclectic tastes lend well to his multiple automotive writing passions.
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