Should I keep my 2014 Jeep Compass in four-wheel drive (4WD) all the time or only when needed? Would it hurt to leave it in 4WD all the time? – Mark, Owatonna, Minn.
Jeep produces, arguably, the most capable offroad vehicles in the world, using a variety of all- or four-wheel-drive systems. Generally speaking, the difference between the two is that 4WD units have a two-speed transfer case between the front and rear wheels that allow more control of power distribution for more severe off-road use.
All-wheel-drive (AWD) systems, such as that in your Compass, operate in two-wheel-drive most of the time, front-wheel driven in your case. When certain parameters are met (slippage or impending loss of grip) they send power to the other axle/wheels. These systems, called Freedom Drive (I or II) by Jeep, are lighter, less complex and easier on fuel because only two wheels are being driven most of the time.
An electronically-controlled coupling in the rear differential of your Compass, monitors wheel speed – actually the difference in wheel speed front and rear. When it detects a difference, it knows there is slippage and transfers some power to the rear wheels. It is also programmed to know when traction is plentiful, such as on the highway, and virtually no power goes to the rear wheels to minimize fuel consumption.
The shift-on-the-fly 4WD LOCK button is there to allow you to do just that, send power to all four wheels all the time. A second Freedom Drive system Freedom Drive II is paired with the Continuously Variable automatic Transmission (CVT). It uses a lower final drive ratio and the CVT to simulate the benefits of the lower gears of a transfer case.
This system is part of the Trail Rated package. In either case, there is little reason to leave the system in the 4WD LOCK position in normal conditions. You will be causing wear on more components and burning more fuel. Let the system work for you unless you encounter poor conditions and want to taka a pre-emptive step.
Airbag injuries
Why don't you hear about the injuries caused by airbags? I have heard of people losing their hearing and having their noses broken. – Donna
The answer is pretty simple, if somewhat harsh. Those injuries are preferable to the alternative – more serious injury or death.
Seatbelts also cause some injury, particularly if not worn properly. But here again, the alternate is unacceptable.
An airbag deployment is a violent event. The bag has to be fully inflated before the face and body, catapulted forward by the forces of gravity, impact the wheel or instrument panel. The latest generation bags are much more sophisticated than earlier ones. They know where the person is sitting, their approximate weight and the force of the crash, deploying at appropriate speeds.
For example they have to deploy with more force, i.e. more quickly if the occupant is very heavy or sitting close to the instrument panel or steering wheel. The heavy person will be propelled forward more quickly and the smaller one is closer to the danger area.
The potential for injury is greatly reduced if the person is wearing the belts properly because they will be partially prevented from going too far forward – into the bag as it is being deployed – sort of like running into a punch. The best way to avoid or at least minimize injuries is to ensure you are seated a safe distance from the bag – an absolute minimum 20 cm. That way you will likely survive to complain about bruises and noise.
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