Can someone enlighten me on the difference(s) between four-wheel drive and all-wheel drive and give me an idea of the advantages and disadvantages of each?
Thanks.
Thanks.
4WD vs. AWD?
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His is a pretty good explanation. http://www.helium.com/items/174070-the-difference-between-all-wheel-drive-and-four-wheel-drive
I think AWD can transfer power front, back and side to side, depending on where traction is needed. 40 front and 60 rear sounds right for a Subaru.
4WD, you have to select and engage. Some have locking hubs on the outside, some are auto locking.
4WD, you have to select and engage. Some have locking hubs on the outside, some are auto locking.
My understanding (on my own vehicle, at least) is open center diff = AWD, locked center diff = 4WD. Then you get into 4H, 4L, rear locker, yadda yadda yadda.
AWD is generally safe for dry pavement. In some vehicles it can be turned off and on. Others it's always on. Always on = beat up the gas mileage.
4WD is generally not safe for dry pavement (in this context, safe in regard to vehicle health-- not risk of personal injury). Also can generally be turned off/on. turned on once again = beat up the gas mileage.
in both cases, they're also good for inducing over-confidence on icy/snow-packed roads. Either drive system may help you with driving traction on slick surfaces, but neither drive system helps you stop
AWD is generally safe for dry pavement. In some vehicles it can be turned off and on. Others it's always on. Always on = beat up the gas mileage.
4WD is generally not safe for dry pavement (in this context, safe in regard to vehicle health-- not risk of personal injury). Also can generally be turned off/on. turned on once again = beat up the gas mileage.
in both cases, they're also good for inducing over-confidence on icy/snow-packed roads. Either drive system may help you with driving traction on slick surfaces, but neither drive system helps you stop
This is the most correct explaination I could find quickly.
http://www.autotrader.com/research/article/car-advice-buying/26180/4wd-or-awd.jsp
There are better, more detailed explainations, but this covers the basics.
For me AWD is not as good of an option if you are planning to drive off-road or in deep snow. AWD is good for keeping you on the road in wet or slippery conditions, or on gravel roads. This is due to the fact that the power does not go to all 4 wheels at the same time, there is always an un-even split of power to the wheels, side to side or front to back. The other draw back to this is that more parts are moving per mile driven, with no option to dis-engage it, which can equal bigger repair bills.
4WD is better for when you are planning to go off road, driving in deep snow, or mud, due to the fact that the power is split more evenly front to rear and side to side.
4WD is usually not good for pavement, and will eventually ruin it (due to the more even power split) if run on dry pavement for a long time, which is why there is the option to turn it off. Turning it off also gives a minor (very minor) fuel savings, also resulting in less parts moving per mile, meaning possibly less repairs.
It really comes down to the types of driving you plan on doing. If you plan on staying mostly on road, and drive in un-favorable weather, then AWD may be the better option, but if you need to traverse a mountain, pull a trailer in snow, run in the mud, or on steep or more challenging (than gravel or a minor dirt road ) trails you would be better off with 4WD.
Also, I am by no means an expert, I just enjoy outdoor sports including off-roading
http://www.autotrader.com/research/article/car-advice-buying/26180/4wd-or-awd.jsp
There are better, more detailed explainations, but this covers the basics.
For me AWD is not as good of an option if you are planning to drive off-road or in deep snow. AWD is good for keeping you on the road in wet or slippery conditions, or on gravel roads. This is due to the fact that the power does not go to all 4 wheels at the same time, there is always an un-even split of power to the wheels, side to side or front to back. The other draw back to this is that more parts are moving per mile driven, with no option to dis-engage it, which can equal bigger repair bills.
4WD is better for when you are planning to go off road, driving in deep snow, or mud, due to the fact that the power is split more evenly front to rear and side to side.
4WD is usually not good for pavement, and will eventually ruin it (due to the more even power split) if run on dry pavement for a long time, which is why there is the option to turn it off. Turning it off also gives a minor (very minor) fuel savings, also resulting in less parts moving per mile, meaning possibly less repairs.
It really comes down to the types of driving you plan on doing. If you plan on staying mostly on road, and drive in un-favorable weather, then AWD may be the better option, but if you need to traverse a mountain, pull a trailer in snow, run in the mud, or on steep or more challenging (than gravel or a minor dirt road ) trails you would be better off with 4WD.
Also, I am by no means an expert, I just enjoy outdoor sports including off-roading
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in both cases, they're also good for inducing over-confidence on icy/snow-packed roads. Either drive system may help you with driving traction on slick surfaces, but neither drive system helps you stop
That's a great point. There are a lot of people out there who seem to think that 4WD/AWD eliminates the need to drive slowly and carefully in the snow. I like having it because it's pretty hilly where I live and we can get a lot of snow, but avoiding over confidence, as you say, is very important.
Thanks for all the responses. We're trying to figure out what our next vehicle will be, and this is helpful.
Next question: I currently have a Honda Pilot that they call 4WD rather than AWD. It's not an off road vehicle, obviously. Am I correct that its "4WD" because it's a part time system that theoretically operates in FWD mode unless conditions call for 4WD? (I say "theoretically" because there is no indicator to tell the driver when 4WD is engaged.)
Thanks guys.
It depends. Does it give you the option to override the system and lock into 4WD? If it does, then I would say you have a 4WD, but if it does not then you have basically an "Intelligent 4WD" (or "Smart AWD"or what ever Honda, ford, etc, decide to call it.)
Yet again, I am not an expert.
As everyone has stated above there is a difference. I think it is important to know what vehicles you are talking about though, or if it is just a general question.
Typically with 4WD you have a vehicle that has a selectable transfer case. Most AWD vehicles I believe and could be wrong but they do not have a selectable transfer case. With that being said, my wife drives a 07 Jeep Grand Cherokee. It is technically 4WD but you can not select 2WD. So I would label it more of a AWD. But it does have the ability to select 4WD Low Range. The low range will changes the gear ratio in the transfer case and will allow you to have more torque at the wheel. It is not for high speed driving. Because of the set up in the Grand Cherokee, it is absolutely amazing in the snow. It also has traction control and skid protection. I have tried to make it slide in the snow and it won't let me. But I don't rule out that as a possibility driving on the highway, no matter the confidence I have in the vehicle. (as a side note, I grew up in a lot of snow during the winter, I learned to drive in snow because I had to. There for I am very comfortable driving in snow).
I do not believe that the newer AWD vehicles are any worse on gas than a 2WD option. Most are built to put as little wear and tear on the drive system as possible, and to be efficient. You might loose 1 or 2 miles per gallon. The vehicle does have more weight to it because of the extra parts for the AWD. It would also depend on how you drive. If you are driving where the system is constantly moving and engaging then the mileage would not be as good.
I drive a 99 Jeep Cherokee. It is a true 4WD. I can select 2WD, 4WD High Range, and 4WD Low Range. My Jeep has a mechanical transfer case. I pull a lever next to the gear selector that will put the Jeep in 4WD. The transfer case has the ability to let the 4WD High Range engage at any speed. 4Lo is different and you have to be less than 5 mph or stopped. There is an electronic 4WD system. Those would be the push button variety. I question the reliability of them and feel more comfortable with my lever. When I pull the lever I know it is engaging, and if some thing bends or breaks I can fix it, on the side of the road/trail if I have to. I hate chasing electric gremlins.
There are also some 4WD transfer cases that you can drive on dry pavement and not hurt the vehicle. My first Cherokee was an 88, and it had an option for Full Time 4WD. The low and high range are typically Part Time 4WD. If you drive with Part Time 4WD engaged on dry pavement you have potential for damage to the transfer case and the differentials. With that said, I know the reliability of the full time transfer case was not as good as the part time only ones. And I have no idea how it worked.
What happens when you turn a corner in you vehicle the out side wheel will have to rotate faster than the inside wheel to drive through the corner smoothly. That is the basic idea behind a differential, it allows the out side wheel to rotate faster. If 4WD is engaged, the differential will not have the same amount of "play." The front drive shaft is putting power into the differential and turning on dry pavement will cause the drive shaft to bind, that is why you might feel a skipping or choppy turn. Kind of like a bounce in the steering wheel. Enough of this will damage the vehicle, and it is expensive to fix if you do. AWD vehicles do not have this problem. And if your 4WD vehicle is in 2WD then you will not have this problem either.
Then some vehicles have locking hubs on the front axle. They are basically a way to disengage the front axle further for more 2WD. I don't know how to really explain it but there is less stuff engaged on the front axle, so there is less wear and tear on it. My Cherokee does not have this but some older Jeeps did come with it.
My wife's Grand Cherokee is more computer controlled. It will send power to the wheel that has traction. It does have a limited slip differential in both the front and rear axle. So with holding a little pressure on the brake, all 4 wheels will engage and power will go to all 4 wheels, making it a true 4WD. If my Jeep were stock and not built for off road, my wife's Jeep would be more capable than mine because of this.
So for me, off roading is a hobby, the 4WD in my Jeep Cherokee is a better option. There are situations that I want as much control as I can over the vehicle, and that is what I have.
In my opinion the AWD is more of an effortless/thoughtless option. You don't have to think if you need 4WD, the vehicle takes care of that for you. Also my experience is with Jeeps, for the most part, and not with AWD systems. I know very little about Subarus or other AWD cars.
So in summary. There are lots of differences, but depending on the vehicle and type of driving you do they will accomplish the same thing, and possibly with out you knowing the difference.
Typically with 4WD you have a vehicle that has a selectable transfer case. Most AWD vehicles I believe and could be wrong but they do not have a selectable transfer case. With that being said, my wife drives a 07 Jeep Grand Cherokee. It is technically 4WD but you can not select 2WD. So I would label it more of a AWD. But it does have the ability to select 4WD Low Range. The low range will changes the gear ratio in the transfer case and will allow you to have more torque at the wheel. It is not for high speed driving. Because of the set up in the Grand Cherokee, it is absolutely amazing in the snow. It also has traction control and skid protection. I have tried to make it slide in the snow and it won't let me. But I don't rule out that as a possibility driving on the highway, no matter the confidence I have in the vehicle. (as a side note, I grew up in a lot of snow during the winter, I learned to drive in snow because I had to. There for I am very comfortable driving in snow).
I do not believe that the newer AWD vehicles are any worse on gas than a 2WD option. Most are built to put as little wear and tear on the drive system as possible, and to be efficient. You might loose 1 or 2 miles per gallon. The vehicle does have more weight to it because of the extra parts for the AWD. It would also depend on how you drive. If you are driving where the system is constantly moving and engaging then the mileage would not be as good.
I drive a 99 Jeep Cherokee. It is a true 4WD. I can select 2WD, 4WD High Range, and 4WD Low Range. My Jeep has a mechanical transfer case. I pull a lever next to the gear selector that will put the Jeep in 4WD. The transfer case has the ability to let the 4WD High Range engage at any speed. 4Lo is different and you have to be less than 5 mph or stopped. There is an electronic 4WD system. Those would be the push button variety. I question the reliability of them and feel more comfortable with my lever. When I pull the lever I know it is engaging, and if some thing bends or breaks I can fix it, on the side of the road/trail if I have to. I hate chasing electric gremlins.
There are also some 4WD transfer cases that you can drive on dry pavement and not hurt the vehicle. My first Cherokee was an 88, and it had an option for Full Time 4WD. The low and high range are typically Part Time 4WD. If you drive with Part Time 4WD engaged on dry pavement you have potential for damage to the transfer case and the differentials. With that said, I know the reliability of the full time transfer case was not as good as the part time only ones. And I have no idea how it worked.
What happens when you turn a corner in you vehicle the out side wheel will have to rotate faster than the inside wheel to drive through the corner smoothly. That is the basic idea behind a differential, it allows the out side wheel to rotate faster. If 4WD is engaged, the differential will not have the same amount of "play." The front drive shaft is putting power into the differential and turning on dry pavement will cause the drive shaft to bind, that is why you might feel a skipping or choppy turn. Kind of like a bounce in the steering wheel. Enough of this will damage the vehicle, and it is expensive to fix if you do. AWD vehicles do not have this problem. And if your 4WD vehicle is in 2WD then you will not have this problem either.
Then some vehicles have locking hubs on the front axle. They are basically a way to disengage the front axle further for more 2WD. I don't know how to really explain it but there is less stuff engaged on the front axle, so there is less wear and tear on it. My Cherokee does not have this but some older Jeeps did come with it.
My wife's Grand Cherokee is more computer controlled. It will send power to the wheel that has traction. It does have a limited slip differential in both the front and rear axle. So with holding a little pressure on the brake, all 4 wheels will engage and power will go to all 4 wheels, making it a true 4WD. If my Jeep were stock and not built for off road, my wife's Jeep would be more capable than mine because of this.
So for me, off roading is a hobby, the 4WD in my Jeep Cherokee is a better option. There are situations that I want as much control as I can over the vehicle, and that is what I have.
In my opinion the AWD is more of an effortless/thoughtless option. You don't have to think if you need 4WD, the vehicle takes care of that for you. Also my experience is with Jeeps, for the most part, and not with AWD systems. I know very little about Subarus or other AWD cars.
So in summary. There are lots of differences, but depending on the vehicle and type of driving you do they will accomplish the same thing, and possibly with out you knowing the difference.
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That sounds right. We can only lock into 4WD at low gear at low speed, as I mention below, but during normal use we can't override the system.
Just a general question at this point, but as I mentioned we are looking for another car/vehicle. (I've always wanted a Jeep Wrangler but they're not really practical for my current needs and get very poor mileage.
Not that my Pilot is setting any records in that regard, unfortunately.) We have a similar feature on the Pilot that allows us to lock into 4WD in low gear at low speed. It works in the two low gears on the automatic transmission, but not in drive unless I'm mistaken. It also disengages automatically at around 18 mph. It was very useful when it came to getting out of my driveway in the midst of last winter's blizzard.
I grew up driving in snow as well. My wife didn't, however.
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Sounds similar to the Grand Cherokee. I have only used 4 low once in it and I am pretty sure it will disengage at a certain speed, but I have no idea where that is. In the Grand 4 low will also turn off the traction control and skid protection. Some times you want wheel spin in an off road, or snow, or mud, or all of the above situation.
Just a general question at this point, but as I mentioned we are looking for another car/vehicle. (I've always wanted a Jeep Wrangler but they're not really practical for my current needs and get very poor mileage.
How much snow do you get? Do you plan on going off road where you need 4WD? Do you really need a 4WD? Is the vehicle for you or your wife?
4WD does not mean 4 wheel stop. Lots of people are under the impression 4WD helps in braking, over all vehicle control also. I can assure you from my many hours under my Jeep, the brakes and 4WD system are in no possible way connected. I see a lot of inexperienced drivers end up in the ditch because they think the 4WD will make them drive better in adverse conditions. It only helps you go, not stop or turn. Actually a skid with a vehicle that has 4WD engaged can be more difficult to correct than a front or rear wheel drive.
I do not necessarily need 4WD and neither does my wife. But off roading is a hobby of mine and we live in Colorado and spend a lot of time in the mountains. So the 4WD in both vehicles has saved us many times, and it gets used frequently. We hit a snow storm last year in September in the mountains, with out the 4WD we probably would have stopped for the night.
In my opinion, 4WD is not a necessity. If you keep it on the pavement AWD or 2WD will get you any where you need to go. But where I grew up almost every family had at least 1 4WD for the snow, we did need it there, and there are other places like that, so for some it is a necessity.
Keep in mind what you want it for.
Here in Norway, the winter is long and snowy/slippery conditions are very common. Yet I manage just fine with my fwd compact car. AWD cars can make it easier to drive in bad conditions - but it's never a replacement for driving skills. (Besides - recovering a big & heavy 4wd suv from a nasty skid is harder than a more normally sized car.)
It makes a difference when it comes to steep hills in snowy conditions. But it takes a very steep hill to make it a problem if your tires are good.
However, there's this fantastic new invention that does make up for lack of skill when driving in bad conditions - even the most skilled driver can't match it. ESP/ electronic stability control. It brakes individually on all 4 tires when it detects that the car is out of controll. It takes controll of the wheel. You can't match it - and it really improves safety, especially in suvs, since it drasticly reduces the chances of a rollover. It can't bend the laws of physics - but it's better than any human driver at recovering a skid.
A demonstration: http://www.youtube.com/watch?v=m5Ug-udF4V0 especially the side-by-side view near the end is good. Audio is swedish, but the results speak for themselves. (It's basicly just a quick talk about what it is, and some governement official that mentions that it would lots of lives if every swedish car had esp.)
If there's cars with esp in your pricerange it would be foolish not to get it. It's one of the more noticeable safety improvements in modern automobiles for bad conditions. In regions with long & nasty winters it saves lives, and reduces stupid accidents.
Here in Norway, the winter is long and snowy/slippery conditions are very common. Yet I manage just fine with my fwd compact car. AWD cars can make it easier to drive in bad conditions - but it's never a replacement for driving skills. (Besides - recovering a big & heavy 4wd suv from a nasty skid is harder than a more normally sized car.)
It makes a difference when it comes to steep hills in snowy conditions. But it takes a very steep hill to make it a problem if your tires are good.
However, there's this fantastic new invention that does make up for lack of skill when driving in bad conditions - even the most skilled driver can't match it. ESP/ electronic stability control. It brakes individually on all 4 tires when it detects that the car is out of controll. It takes controll of the wheel. You can't match it - and it really improves safety, especially in suvs, since it drasticly reduces the chances of a rollover. It can't bend the laws of physics - but it's better than any human driver at recovering a skid.
A demonstration: http://www.youtube.com/watch?v=m5Ug-udF4V0 especially the side-by-side view near the end is good. Audio is swedish, but the results speak for themselves. (It's basicly just a quick talk about what it is, and some governement official that mentions that it would lots of lives if every swedish car had esp.)
If there's cars with esp in your pricerange it would be foolish not to get it. It's one of the more noticeable safety improvements in modern automobiles for bad conditions. In regions with long & nasty winters it saves lives, and reduces stupid accidents.
I like Four Wheel and off Road's definition. 4 wheel drive has a two speed transfer case. That's when you see 2H, 4H, and 4Lo on the selector switch or handle, depending on the year of the vehicle. AWD is just that, a trasfer of power to all 4 wheels. There is no 4 Low. Most of the time you have no control over it. As far as locking differentials go, most companies do not offer them, even Jeep does not offer them on most models. The Wrangler Rubicon has one in the rear I believe.
The Rubicon has a locking diff on the front and the back. There is another Wrangler that does have a rear lockable diff. Some Toyotas came with a lockable diff also but I am not sure if any of the newer models do. I do not know of any other companies that have that as an option, maybe Land Rover.
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I agree with you. Honestly, front-wheel drive would be fine for 99% of the conditions we experience, and if we really need 4WD we can use the Pilot. To answer your question, my wife and I would probably each drive both cars depending on who has the kids, etc. She grew up in the South and is understandably nervous about driving in the snow, so the 4WD/AWD provides her with more peace of mind. Fortunately, she's too smart to take a cavalier attitude toward driving in the snow even with 4WD!
Honda AWD..
Real Time 4WDThe remarkable Real Time 4-wheel drive system, available on all CR-V trim levels, increases drivetrain efficiency, decreases noise and vibration, and only operates in 4WD when necessary. Here is how it works: When there is insufficient traction at the front wheels, the Real Time 4WD system automatically uses dual hydraulic pumps to transfer power to the rear wheels. There is no need for driver intervention. The greater the degree of front-wheel slippage, the more torque is directed to the rear wheels. Best of all, Real Time 4WD requires little maintenance.
Honda Grade Control..
Grade Logic ControlAutomatic transmissions use Honda's Grade Logic Control system. This system differs from other computer-controlled shift programming because it can detect vehicle driving situations and then set appropriate shift points for the car. This feature avoids gear hunting on ascents and descents, and downshifts for added engine braking.
Honda Vehicle Stability Assist..
Vehicle Stability Assist (VSA®) with Traction ControlThis sophisticated safety device aids the driver in retaining control of the vehicle if wheel slippage is detected. When the driver is cornering or must make a sudden maneuver, the system can sense oversteer and understeer and can brake individual wheels and/or reduce power to restore the driver's intended course.
Honda Pilot Variable Torque Management (4WD tagged)..
Variable Torque Management® (VTM-4®) 4-Wheel Drive SystemThe VTM-4® system operates automatically. But when you need to start off in extreme low-traction conditions, such as when stopped in mud, on ice or in loose gravel, the VTM-4Lock® feature lets you manually lock the rear differential to help get you moving. And it will stay manually locked up to 18 mph in both forward and reverse gears.
Basically the same as AWD except you can lock the rear differential to help you out of mud, snow, whatever. Above 18mph you than have AWD.
I am on my second CR-V with AWD and have never had problems in snow or two track sand roads in MI.
Real Time 4WDThe remarkable Real Time 4-wheel drive system, available on all CR-V trim levels, increases drivetrain efficiency, decreases noise and vibration, and only operates in 4WD when necessary. Here is how it works: When there is insufficient traction at the front wheels, the Real Time 4WD system automatically uses dual hydraulic pumps to transfer power to the rear wheels. There is no need for driver intervention. The greater the degree of front-wheel slippage, the more torque is directed to the rear wheels. Best of all, Real Time 4WD requires little maintenance.
Honda Grade Control..
Grade Logic ControlAutomatic transmissions use Honda's Grade Logic Control system. This system differs from other computer-controlled shift programming because it can detect vehicle driving situations and then set appropriate shift points for the car. This feature avoids gear hunting on ascents and descents, and downshifts for added engine braking.
Honda Vehicle Stability Assist..
Vehicle Stability Assist (VSA®) with Traction ControlThis sophisticated safety device aids the driver in retaining control of the vehicle if wheel slippage is detected. When the driver is cornering or must make a sudden maneuver, the system can sense oversteer and understeer and can brake individual wheels and/or reduce power to restore the driver's intended course.
Honda Pilot Variable Torque Management (4WD tagged)..
Variable Torque Management® (VTM-4®) 4-Wheel Drive SystemThe VTM-4® system operates automatically. But when you need to start off in extreme low-traction conditions, such as when stopped in mud, on ice or in loose gravel, the VTM-4Lock® feature lets you manually lock the rear differential to help get you moving. And it will stay manually locked up to 18 mph in both forward and reverse gears.
Basically the same as AWD except you can lock the rear differential to help you out of mud, snow, whatever. Above 18mph you than have AWD.
I am on my second CR-V with AWD and have never had problems in snow or two track sand roads in MI.
X2. When I spent a couple of years out in central Oregon, there was plenty of snow and ice, but I made it around with FWD and a 5 speed. Since there wasn't much going on out there, I used to drive it all over the dirt fire service roads, too.
