By Allen Penticoff
This is the fourth in a four-part series on common drivetrains. In fact, it was thinking about how pervasive all-wheel-drive (AWD) has become that prompted me to create the series. Having just sold our 1997 Subaru Outback Wagon that had AWD, I noticed just how many new cars were being offered with AWD as an option.
As I reported in the previous “Mr. Green Car” column, four-wheel-drive has been around for a long time. However, the concept of having full-time four-wheel-drive is a relatively new technology (if you consider 1979 as being fairly new), for that is when American Motors Corporation (AMC) introduced their Eagle line.
Based on the AMC Concord platform, a front differential was installed and a slipping transfer case was employed that allowed the car to be driven in four-wheel-drive all the time without binding. In comparison tests against other four-wheel-drives of the time, it had clear performance advantages and was noted as being the forerunner of a new class of vehicle. Indeed, the AMC Eagle was the progenitor of the SUV “Crossover” passenger car with 4×4 capabilities.
AMC salesmen only had to take a prospective customer out to a steep, snow-covered street, stop, then ask the customer to hit the gas. The Eagle would sprint up that street with nary a bit of wheel spin. They were sold. Rural mail delivery was by Eagle in any snowy climate. Some still drive them. Their straight-six engine was very durable. AWD had proven advantages in race cars as well — so advantageous that most race car classes were re-defined to exclude AWD cars.
Unlike part-time 4×4 systems, AWD cannot be turned off. There are no hubs that need locking. It is simple for the driver, as there is no choice. It is sold as being safer, and to some extent, it is. Even in the rain, I’ve found the Subaru would take off as though on dry pavement — leaving faster cars like Mustangs far behind, trying to get traction. In snow, it was similar. Pulling out onto a street with traffic coming, there was never any doubt that you could get out into the lane, rather than wonder if the wheels would spin. I even think the AWD handled potholes better, as the tires climbed out of the holes rather than bouncing out of them.
One thing that must be remembered about AWD vehicles is that it is really quite easy to get going too fast in snowy or wet conditions — too fast to stop safely. They do not stop any faster than a 2WD vehicle in these conditions. I’ve had many a close call because of this fact. You also tend to be less patient with others who are struggling to go in the snow and will make bold attempts at passing. Not so safe, either.
It is also entirely possible to have all four tires lose their grip in a turn; now, you can’t steer or go either, and the car will drift in the direction toward the outside of the turn. Fortunately, lifting your foot off the accelerator will usually regain control. AWD also has great handling on dry pavement, too — with all the tires doing nearly the same amount of work.
But for all these advantages, there are some downsides. AWD, like part-time 4×4, adds a lot of complexity to the drivetrain. The transfer case, the extra drive axles and extra CV joints add weight and cost. It takes more power to move all these parts all the time and, as a consequence, fuel economy is lower than a similar two-wheel-drive model. Our Subaru typically got 20 mpg city and 24 mpg highway. Most 2WD cars of its size would be attaining 25 mpg city and 30 mpg highway. Roughly a 20 percent greater fuel cost we paid all the time, although we rarely needed the AWD capabilities. There are, however, some new cars out that have minimized the weight and drag penalties of AWD and do get respectable fuel economy. Also, some new hybrid systems will use the engine to power the front wheels while the electric motor drives the rear wheels; this is a logical combination that I believe we will see more of in the future.
Another never-advertised fact about life with AWD is that all the tires must be of equal size. If one tire is substantially different than the other four, it will cause slippage in the axle it is on and in the transfer case. This slippage will wear out the clutches in these parts, and a huge repair bill will come with the eventual repair. If you get a damaged tire on an older set of tires, you probably cannot find another used one that matches the wear of the old one, and even a new one of the same brand and model will be bigger and not equal to the other three on the car — so, you end up buying four new tires because one is bad. Been there, done that. It is this kind of expense that caused us to give up on the expensive-to-maintain Subaru and go back to front-wheel-drive cars for all-season use.
And this is why I wrote this column. Highly profitable AWD is pushed by the manufacturers — and buyers fall for its touted advantages without being aware of some of the disadvantages. If you truly need four-wheel-drive on a regular basis, then you should buy this feature. Subarus are practically the official state vehicle of Colorado because they deal with snow far more often than we in the Midwest do. But if you are going on one ski trip to Colorado a year, AWD is not needed to get you there — though at times it would be nice. You have to decide if the added expense of fuel and maintenance is worth this occasional need.
I hope this series has made you more aware of the many choices available to us as consumers of the many varied transportation options. There are many factors that weigh in on a purchase. I, for one, am wrestling with justifying buying a Chevy Volt. In my mind, it has all I need in a car, and while not cheap, is in the price league with many other cars — particularly those that feature AWD. I would rather have the option to drive some pollution-free miles each day, rather than worry about getting through a handful of snowstorms each year. I’ve noticed pretty much everyone gets where they need to go without too much difficulty regardless of what the weather is and what they are driving.
From the March 20-26, 2013, issue