4MATIC All Wheel Drive

Ten years ago, very few vehicles other than trucks and Audi Quattros put power to the pavement through all four wheels. The drivetrain landscape has since changed dramatically. Many new cars come standard with all wheel drive (AWD), and for many more AWD is optional.

Mercedes reintroduced its 4Matic all wheel drive system in 1998 with the E320. Think of the 4Matic as the baby brother of the AWD system found in the Mercedes ML-class SUV. Plagued by reliability issues, the original 4Matic system disappeared from the market in 1993. Let’s take a look at why the early 4Matic failed and why the new 4Matic is far superior.

The Early 4Matic: 1987-1993

The first generation 4Matic sold in the early ’90s is a part-time all wheel drive system. In normal driving conditions, with no wheel slippage, the system directs all power to the rear wheels. When the computer detects rear wheel spin, it activates a series of clutches that engage and lock in the front axles for more traction. When braking, the system quickly disengages the front axle to avoid interference with the anti-lock brakes.

This system does not in any way prevent wheel spin or keep the car stable once moving. It only switches on the front wheels after the rear wheels lose grip. Because this system waits for wheel slippage to occur before powering the front wheels, it is a reactive system.

The only advantage of this system is that its complete disengagement completely preserves the rear wheel drive handling dynamics in dry conditions.

The disadvantages of this reactive system are numerous. (1) When the AWD is not in use (which is most of the time), the car lugs around more than 200 lbs of extra dead weight in the all wheel drive system. This hurts gas mileage. (2) The system does not increase the car’s stability. It only gets the car unstuck after a brief lag time for engagement. (3) The complicated electrical and hydraulic parts leak and break down often.

The New 4Matic: 1998-Present

For the new 4Matic system, Mercedes tossed out the old 4Matic design and contracted German engineering firm Magna Steyr to build a new system from scratch. The new system works just like an extended version of a typical rear wheel drive car. It adds little complexity, which means that it’s unlikely to break.

Here’s how it works. All rear wheel drive cars have a rear differential that splits torque between the back left and back right wheels. To the base E-class design, the 4Matic system adds a front differential that splits torque between the front left and front right wheels. A center differential then splits torque between the front (35%) and rear (65%). This system does not involve any complicated clutches or differential locks that could wear out or cause trouble.

It is on all the time, which means that it prevents wheel slip and improves stability. Because of this, the new 4Matic system is a full-time, proactive system.

But it’s also reactive to wheel slip. On an ordinary two wheel drive car without differential locks, if one drive wheel loses traction, the car can’t move. For an all wheel drive car without locks, the situation worsens. If any of the four wheels lose grip, the car gets stuck. To solve this problem, Mercedes used the same technique as a two wheel drive car: electronic traction control. Electronic traction control gently brakes the wheel that slips, causing the differential to send power to the wheels that grip. Theoretically, the 4Matic system can move the car even if only one wheel has traction.

For more information about the 4Matic system, see Wolfgang’s 4×4 ASR ETS 4ETS 4MATIC page.

Practical Matters

Is 4Matic really necessary?

Probably not, even in snowy climates, provided that you use snow tires in the winter. Remember that all wheel drive does not help the car brake or steer any better. All cars have “all wheel brakes!” All wheel drive only accelerates you more quickly. All that traction when accelerating can make you overconfident when cornering or braking.

The all wheel drive system adds about 200 pounds. It takes longer to stop a heavier vehicle than a lighter one. In snow, the 4Matic takes about 10 feet longer to stop — which could be the difference between an accident and rear-ending someone.

Although you can make it through snow to your destination with rear wheel drive and snow tires, the 4Matic will get you there without any fuss or drama. If you have snow tires, ESP (that’s electronic stability control, not extra-sensory perception!), and 4Matic, your car will be heavy duty snow tank. Only ground clearance can stop you!

Car and Driver (unauthorized reprint?): In winter, what’s best: Two wheel drive on snow tires, or four wheel drive on all season tires?

Does the 4Matic hurt gas mileage or performance?

The impact on gas mileage is minimal — about a 1 MPG drop. 0 to 60 times increases by about a quarter second. Directional stability is improved by all wheel drive.

Should I be concerned about reliability with the 4Matic?

No. The 4Matic adds no new parts. Just two extra differentials. The traction control system is already used on the regular rear wheel drive car. The difference in reliability between 4Matic and rear wheel drive is analogous to the difference in reliability between a four cylinder and an eight cylinder. It’s a non-issue.

How does 4Matic affect resale value / purchase price?

Since all wheel drive is so popular, the 4Matic option adds about $2,000 to the purchase price of a used E-class, especially in the snow belt. 4Matic cars have held their value better than their garden variety RWD siblings. They will probably continue to comand a price premium in the future.