Edmunds Answers

Voted Best Answer

  • avatar zaken1 06/09/11 2:41 am PST

    AWD is a system in which engine power is routed to all four wheels at all times; but the amount of power each wheel receives is automatically adjusted according to the driving conditions. AWD is designed to work on dry highways and also work in snow and ice. In each of those conditions; the power delivery is adjusted to minimize slippage (when on slippery surfaces) and maximize tire life (when on dry surfaces).

    4WD is an older system, in which power always drives the rear wheels; but power to the front wheels has to be engaged manually by getting out of the vehicle and turning knobs on the front hubs. It is also necessary to shift a lever inside the vehicle to engage 4WD. 4WD is not supposed to be used on dry pavement; it is only for use in snow, ice, and deep mud. Using 4WD reduces fuel economy and shortens tire life.

    Some recent vehicles have a modified 4WD system, called "shift on the fly." These systems can be manually shifted in and out of 4 wheel drive while the vehicle is moving; but it is still not intended for full time use.

Answers

  • zaken1 06/09/11 2:41 am PST

    AWD is a system in which engine power is routed to all four wheels at all times; but the amount of power each wheel receives is automatically adjusted according to the driving conditions. AWD is designed to work on dry highways and also work in snow and ice. In each of those conditions; the power delivery is adjusted to minimize slippage (when on slippery surfaces) and maximize tire life (when on dry surfaces).

    4WD is an older system, in which power always drives the rear wheels; but power to the front wheels has to be engaged manually by getting out of the vehicle and turning knobs on the front hubs. It is also necessary to shift a lever inside the vehicle to engage 4WD. 4WD is not supposed to be used on dry pavement; it is only for use in snow, ice, and deep mud. Using 4WD reduces fuel economy and shortens tire life.

    Some recent vehicles have a modified 4WD system, called "shift on the fly." These systems can be manually shifted in and out of 4 wheel drive while the vehicle is moving; but it is still not intended for full time use.

  • Stever@Edmunds 06/09/11 8:45 am PST

    Posters in the 4WD & AWD systems explained discussion in the Edmunds Forums go into a lot of detail about various systems from the different brands.

    Post number 2 in that discussion is good, and for a real education on the various nuances, you can read all 1400 posts. :-)

    There is one version of 4WD with a center differential that is permanent--all four wheels are engaged all the time. The definitions get fuzzy fast since every manufacturer defines their system differently.

    Source: 

  • plekto 06/09/11 12:07 pm PST

    It depends upon your application, though. In what most Americans think of AWD as being good for, which is snow and terrible conditions like mud and ice, 4WD is far superior. But it's only meant to ever be used in such conditions. It allows you to climb up hills, go through a foot of snow, and so on. But it's part-time. You have to plan ahead. Most systems also can't be driven for long periods on pavement.

    The military, the forest service, pretty much everyone who lives in Alaska, and so on, all use 4WD systems. It's for when you really are worried about getting stuck and it's hit the fan already.

    AWD comes in two main varities. Full-time systems that are mostly good for rain, gravel/dirt roads, and dry pavement only, but that do improve handling considerably. But they aren't really designed for serious off-roading or extremely bad weather. Basically it's a lighter version of 4WD that's usable on any road surface/in engaged all of the time. Since this is what 90% of people are likely to encounter, it's a good compromise. Subaru is the best known example, though other fully-engaged AWD systems do exist (Mitsubishi EVO, and Audi Quattro as examples).

    The other types are part-time AWD and are pretty much only good for getting you unstuck from snow and the like when you start your car in the morning. They react far too slowly to be of any real use on bad roads by themselves, and it's only with the addition of stability control and a lot of computing power that most of them keep from flying off the road in rain. These should, IMO, be avoided. Unfortunately, these make up 80-90% of the AWD market. People think that they are getting safety and bad-weather driving performance and in reality, they are getting pretty much nothing for their money other than maybe getting out of their driveway.

  • Stever@Edmunds 06/09/11 12:52 pm PST

    I had a manually operated 4WD CJ-5 long ago in TN. I had FWD during 20 Alaskan winters. I have an AWD Outback for ski trips and life in the UP (200" of snow last winter). But I also have a FWD and I much prefer FWD for 99.9% of my driving. In fact, I may dump the Outback and just buy mounted snow tires one of these days for winter driving.

    About the only car I don't want for snow is a RWD one, but the best snow car I had in Alaska for a RWD SuperBeetle. It would go anywhere.

    Some call the Isuzu Trooper a full-time 4WD instead of a "permanent" 4WD. Also the Toyota Sequoia and Mitsubishi Montero. All I learned when I had the Jeep was that 4WD gave you the ability to get stuck further off the pavement.

  • plekto 06/09/11 5:57 pm PST

    Heh.

    Still, part-time power transfer type systems react far too slowly to be useful except at extremely slow speeds. ie - snow and mud and the like. They do nothing for normal "bad weather" driving conditions at any reasonable speed. The system has to be on all of the time to do that.

    You unfortunately have to shop and research carefully as most manufacturers don't actually tell you which system they are using up front, or make fancy claims that don't hold up to actual testing.

    If you need bad weather performance, just get a 4Runner or similar SUV with 4WD on it. As long as you don't go too far off the road (heh) you'll be fine.

ADVERTISEMENT

Top Crossover Experts View More

Rank Leader Points
1. texases 165
2. zaken1 140
3. Stever@Edmunds 125
4. morin2 80
5. MrShift@Edmunds 80
6. igozoomzoom 70
7. karjunkie 70
ADVERTISEMENT