When to Select Four-Wheel Drive
Pictures by Nick Taylor and Graham Jackson
It seems like a simple question. Actually, it is a simple question, but as with many other simple questions, the answer can be quite complicated. Let’s start with context. What I’m talking about is engaging four-wheel drive on overland trips which usually involve some form of dirt and off-road component. Overland trips are about getting from point A to point B safely and with as little impact and trouble as possible and often include long sections of improved dirt. To this end all driving should be done in a pre-emptive manner, and this applies to gear (and mode, in newer vehicles) selection.
As a rule of thumb, whenever you leave asphalt for dirt, switch the vehicle into 4WD (for part-time systems), lock the center differential (for full-time systems) and select cross-country or the equivalent for systems with mode selection. Many people hesitate to engage 4WD on improved dirt, thinking there is no need for it, but as Audi proved in the 80s with the Audi Quattro rally car, there really is no downside. Stability is improved, handling is improved, traction is improved and with all of those, confidence and safety are also improved. If you have any doubts, try it; drive the same section of improved dirt in both modes. Using 4WD will settle the vehicle and make it feel more stable. When improved dirt switches to two-track, or any situation where sustained speeds are well below 30mph, switch into low range. Gearing is improved for low speed work, stress on the driveline is reduced (especially on the torque converter in automatics) and the vehicle is primed for any difficult sections encountered. It also makes the driving more relaxed, though this is subjective.
So what about fuel consumption?
The main argument I always get on the recommendations given above is that both 4WD and low range increase fuel consumption, so it is better to stay in 2WD high for as long as you can. That argument, while fully mitigated by knowing your vehicle range and planning ahead, is also not actually true. In July of 2016, Jonathan Hanson and I conducted an experiment to see what the fuel consumption difference would be. We ran the Madigan line in Australia’s Simpson Desert, a 930 kilometer (580 mile) section of two-track that crosses almost 1000 sand dunes in pretty much identical 75 series Land Cruisers with 1HZ engines. Jonathan chose to run in 2WD high range for most of the track only switching to 4WD when he thought he needed it for traction and low range when he needed it for climbing (only on three dunes). Obviously, Jonathan was doing this for science; best practice is to do what I did. I stayed in 4WD low range the entire time until we left two-track at the QAA line for the short run into Birdsville (less than 40 miles) on improved dirt where I used 4WD high range. We had filled both trucks in Alice Springs and filled again in Birdsville. In Birdsville Jonathan added 35.71 gallons and I added 36.13, a difference of 0.4 gallons. His milage was 16.2 MPG and mine was 16.01 MPG. The one thing that might have made a bigger difference was if Jonathan had unlocked his hubs in 2WD, but it’s just not realistic to keep locking and unlocking hubs on a long overland trip.
So while our experiment might not be a definitive test of all conditions and all vehicles, it is a great case study for the actual differences between gear selection while driving very similar rigs at very similar speeds in the same terrain. The results surprised both of us, although Jonathan takes great glee in lauding that 0.4 of a gallon over my ‘heavy’ right foot.
While the journey is what overlanding is all about, making that journey as painless as possible just makes it better for everyone. Switch into 4WD when you hit dirt; drop to low range on two-track. It’s a rule of thumb that serves well.