Not so long ago the world of all-wheel drive (AWD) and four-wheel drive (4WD) was rather simple. Trucks and SUVs had big, beefy transfer cases that provided low range torque for towing and off-roading. And the few AWD cars mostly used center differentials that helped provide better traction and performance.
These technologies were simple and well understood, though not perfect. Now, though, the world has changed and nowhere is that more obvious than the lineup of Fiat Chrysler.
I recently had to drive the company’s full four- and all-wheel drive lineup of more than 14 vehicles on the snowy wastes of a Canadian test track. There I experienced not just extremely capable old-school setups on standouts like the Jeep Wrangler but also the latest and most innovative systems on Fiat-based vehicles like the new Jeep Renegade.
Not only was this a lot of fun ( I mean how often do you get to power-slide a cop car?), but I also had the chance to learn a lot about the advantages and disadvantages of these different systems. So instead of focusing on any one car, here is a whirlwind tour of just about everything the world of all-wheel and four-wheel drive cars and trucks have to offer.
Wrangler and Ram: If it ain’t, broke don’t fix it
At the core of these systems is a transfer case attached to the transmission. Under normal driving, this sends power to the rear wheels, but can also send power to the front by way of a prop shaft.
In the Wrangler and Ram trucks this transfer case can also be fitted with low-range gears — standard on the Wrangler — that allow the engine to supply maximum torque to the wheels. This is great for towing heavy objects like boats or small countries, though not as important when it comes to driving in snowy or other low traction conditions.
On the winter off-road course, slapping the transmission into low-range gave me the feeling that I could tackle not just the 30-degree incline and moguls but drive off into the sunset across frozen rivers and through dense forests.
The downside of these systems is that they are heavy, add friction, and therefore reduce fuel economy, as well as lack traction at high speed.
- Rugged, and durable technology
- Unmatched off-road potential
- Bad for fuel economy
Jeep Grand Cherokee: Teach an old dog new tricks
The Grand Cherokee is one of the mainstays of the entire Chrysler Group. This well appointed SUV features an excellent combination of old-school and trail-proven four-wheel drive with some modern tricks.
Like the Wrangler and Ram family, the Grand Cherokee uses a range of transfer cases, including ones with low range gearboxes (available on Quadra Track II-fitted models). But there is also impressive new technology available.
Top spec Quadra Drive II Grand Cherokees are fitted not just with a transfer case that splits power between the front and rear axles but also an electronically-controlled rear differential. This system uses an electrically powered clutch to split power between the left and right rear wheels, providing increased grip on and off road.
The amazing thing about using this system on both the ice-covered road course and the off-road track was the fact that the Grand Cherokee felt almost as capable as either the Wrangler or some of the all-wheel drive cars like the Dodge Charger. Yet, despite this capability I was cocooned in luxurious leather and wood trim.
The downside of this setup is the price; to get the impressive E-Diff customers have to choose the Grand Cherokee Summit with a starting price of $48,695.
- Off-road chops of traditional 4WD
- Improved on-road handling and traction
- High price of system
Jeep Cherokee and Renegade: Pretty rugged for an Italian
Perhaps the most technically innovative and practically impressive systems are to be found on the two newest Jeeps: the Renegade and the Cherokee. Both of these vehicles are based on platforms sourced from Jeep’s new Italian overlords at Fiat.
At first, that sounds like a marriage made in hell. Thanks to clever engineering, though, these front-wheel drive-based vehicles have some impressive all-terrain performance.
The basis of these systems is what Chrysler calls a Power Transfer Unit (PTU) located on the front axle. The engineers couldn’t use a transfer case, as the Renegade and Cherokee’s powertrain is positioned parallel to the front axle leaving no place for a bulky transfer case.
The PTU, essentially a combination of clutches, can do the same job as a transfer case, but, because it sends power via a clutch, it can also fully disconnect the rear axle, which dramatically improves fuel economy.
I was deeply impressed by the ability of these systems, especially on the snow- and ice-covered road course where the Renegade and Cherokee held traction as well or better than any of their larger cousins. Both felt a little strained on the off-road course, as the system was pushed to its limits. Still, they managed everything that the Wrangler and Grand Cherokee could — pretty damn good for cars that have the DNA of Fiat city cars.
- Cheap both in price and fuel economy
- Excellent on-road traction
- Somewhat limited off-road ability
Chrysler 300, Dodge Charger, and Charger Pursuit: Breathing new life into full-size sedans
It’s not just trucks and SUVs that Fiat Chrysler has given the AWD treatment. Both the Chrysler 300 and Dodge Charger are available with AWD when fitted with the Pentastar V6. These sedans use a fairly typical transfer case set up with a twist.
Under ordinary driving conditions, the transfer case sends no power to the front axle in order to maximize efficiency. The results are twofold. First, a class-leading 27 highway mpg, Second, it preserves the car’s rear-wheel drive character.
This is a welcome benefit for enthusiasts, especially when given the chance to play on a snow-covered track. The Charger and 300, especially with their traction control systems disabled, can produce big slides without losing control. It’s a fun trick; the only downside is that the police will be having more fun.
The law enforcement edition of the Charger, the Pursuit, is the only vehicle in the lineup available with both AWD and the 5.7-liter Hemi V8. The result is truly intoxicating, especially when you get to throw on the lights and sirens. Sadly, unless you want to wait until these vehicles show up at government auctions, you will need to wear a badge or a set of handcuffs to get a ride in one.
- Good fuel economy for AWD
- Great all weather traction
- Hemi V8 only available on police model
Few carmakers show off the beauty of modern 4WD and AWD systems as well as the Chrysler group. Each system has advantages and disadvantages, but Chrysler has done well choosing the right system for the right application. Worthy of special praise and attention is the way that Chrysler has managed to combine the added capability of AWD with impressive fuel economy.
Better still, with the wide array of technology and vehicles offered by different Chrysler brands, there is something for everyone, whether you want to hit the track, the trails, or just make it to the mall for Christmas shopping.