4WD Vs. AWD
Nov 29, 2005, 09:53 PM
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4WD Vs. AWD
Ok, so I was talking to my friend who owns an older early 90's Ford Ranger. It is 4wd but you have to lock the front wheels hubs and then it is a locked 4wd. I was wondering what is the difference between an AWD mechanism and a 4WD mechanism? I was lead to believe that these items work differently in that AWD can function perfectly on dry pavement while if you engauge 4WD on dry pavement it would hurt the transfercase and possibly burn it out. I thought AWD was specifally made for the street while the other 4WD systems are designed to have some slip in the system meaning snow/ice/mud/grass where there is some give and play. He tells me that they are one in the same and that he could drive in 4wd all the time but it eats more gas.
Any solid info on this subject?
Any solid info on this subject?
Nov 29, 2005, 10:14 PM
#2
4wd means all 4 wheels turn at the same speed with the same power delivered to each wheel. AWD has differentials that allow power to be distributed to the wheel that needs it. This comes into play everyday when making turns. A vehicle in 4WD mode cannot turn without the wheels hopping/chirping, because the inner wheels are traveling less distance than the outer wheels, but they are being forced to go the same speed, so it doesn't work well. On an AWD system, the inner and outer wheels are allowed to spin at different speeds. It is true that you can run 4wd on the tarmac all the time, but the speed is usually limited. That's why many trucks now have 4-high and 4-low. The 4H allows you to drive highway speeds whereas the 4L is designed to only be used at low speed for serious hauling or to get out of some deep mud/sand/etc.
Nov 29, 2005, 10:17 PM
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Nice info!
Originally Posted by Warrtalon
4wd means all 4 wheels turn at the same speed with the same power delivered to each wheel. AWD has differentials that allow power to be distributed to the wheel that needs it. This comes into play everyday when making turns. A vehicle in 4WD mode cannot turn without the wheels hopping/chirping, because the inner wheels are traveling less distance than the outer wheels, but they are being forced to go the same speed, so it doesn't work well. On an AWD system, the inner and outer wheels are allowed to spin at different speeds. It is true that you can run 4wd on the tarmac all the time, but the speed is usually limited. That's why many trucks now have 4-high and 4-low. The 4H allows you to drive highway speeds whereas the 4L is designed to only be used at low speed for serious hauling or to get out of some deep mud/sand/etc.
Nov 29, 2005, 10:18 PM
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Originally Posted by Warrtalon
4wd means all 4 wheels turn at the same speed with the same power delivered to each wheel. AWD has differentials that allow power to be distributed to the wheel that needs it. This comes into play everyday when making turns. A vehicle in 4WD mode cannot turn without the wheels hopping/chirping, because the inner wheels are traveling less distance than the outer wheels, but they are being forced to go the same speed, so it doesn't work well. On an AWD system, the inner and outer wheels are allowed to spin at different speeds. It is true that you can run 4wd on the tarmac all the time, but the speed is usually limited. That's why many trucks now have 4-high and 4-low. The 4H allows you to drive highway speeds whereas the 4L is designed to only be used at low speed for serious hauling or to get out of some deep mud/sand/etc.
wow is the a new WARRTOALON?? no flame ther....good job.
Nov 29, 2005, 10:23 PM
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Wow, case closed, I am guessing if you drove 4WD all the time you would KILL your tires huh?
In that case how did the Corvette with Positrac get around the corners, I thought that was a permanent lock of the rear wheels.
In that case how did the Corvette with Positrac get around the corners, I thought that was a permanent lock of the rear wheels.
Nov 29, 2005, 10:28 PM
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if im not mistaken Positrac is a fourm of LSD in the rear....but i might be wrong... www.google.com
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Nov 29, 2005, 11:14 PM
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Originally Posted by Warrtalon
4wd means all 4 wheels turn at the same speed with the same power delivered to each wheel. AWD has differentials that allow power to be distributed to the wheel that needs it. This comes into play everyday when making turns. A vehicle in 4WD mode cannot turn without the wheels hopping/chirping, because the inner wheels are traveling less distance than the outer wheels, but they are being forced to go the same speed, so it doesn't work well. On an AWD system, the inner and outer wheels are allowed to spin at different speeds. It is true that you can run 4wd on the tarmac all the time, but the speed is usually limited. That's why many trucks now have 4-high and 4-low. The 4H allows you to drive highway speeds whereas the 4L is designed to only be used at low speed for serious hauling or to get out of some deep mud/sand/etc.
Thanks for the explination. I've been wondering for years what the difference between 4WD and AWD was.
Nov 29, 2005, 11:24 PM
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You get both part-time and full-time 4WD. Full-time generally means that you can't do anything to make it NOT drive with 4 wheels.
There are cars out there like the Honda CR-V that drive with only the front wheels and when these begin to slip the system transfer some torque to the rear. I think the Skyline work on a vaguely similar principle but back to front and its system can shift a greater proportion of torque around. So, I think in general, marketing speak would call these AWD.
What Warrtalon said is mainly correct. But there are vehicles that claim to be 4WD and have diffs at the centre, front and rear thus not requiring all 4 wheels to go at the same speed. Range Rovers are a good example.
Older vehicles do have all 4 wheels go at the same speed or allow a very small amount of slip. These basically have a really hard time around tight corners and if you put on full steering lock while stationary and try to move off, it will either stall or moves with a horrible noise.
I might be wrong on the Ranger, but cars with hub-locks generally rotate their front axles all the time, they're just not connected to the wheels till you lock them.
In general I don't think there's a real concrete difference between the two, but from what I've seen, 4WD seems to apply to systems that are purely mechanical and AWD seems to suggest a sort of eletronic control system that can shift torque around all 4 wheels.
There are cars out there like the Honda CR-V that drive with only the front wheels and when these begin to slip the system transfer some torque to the rear. I think the Skyline work on a vaguely similar principle but back to front and its system can shift a greater proportion of torque around. So, I think in general, marketing speak would call these AWD.
What Warrtalon said is mainly correct. But there are vehicles that claim to be 4WD and have diffs at the centre, front and rear thus not requiring all 4 wheels to go at the same speed. Range Rovers are a good example.
Older vehicles do have all 4 wheels go at the same speed or allow a very small amount of slip. These basically have a really hard time around tight corners and if you put on full steering lock while stationary and try to move off, it will either stall or moves with a horrible noise.
I might be wrong on the Ranger, but cars with hub-locks generally rotate their front axles all the time, they're just not connected to the wheels till you lock them.
In general I don't think there's a real concrete difference between the two, but from what I've seen, 4WD seems to apply to systems that are purely mechanical and AWD seems to suggest a sort of eletronic control system that can shift torque around all 4 wheels.
Nov 29, 2005, 11:26 PM
#14
a 4 wheel drive system evenly distributes torque between the front and rear drive axle via a direct drive transfer case which is usually attached to the transmission of a vehicle. an all wheel drive system is similar, but all wheel drive systems usually have a center differential which allows the torque split between front and rear axles to vary depending on road conditions.
4 wheel drive systems are generally better for off roading since they have no center differential that can unload if one axle loses traction. 4 wheel drive systems are generally much tougher than all wheel drive systems which makes them better for off road use since they can withstand higher torque loads, and lower gearing can be used.
http://www.howstuffworks.com/four-wheel-drive.htm
4 wheel drive systems are generally better for off roading since they have no center differential that can unload if one axle loses traction. 4 wheel drive systems are generally much tougher than all wheel drive systems which makes them better for off road use since they can withstand higher torque loads, and lower gearing can be used.
http://www.howstuffworks.com/four-wheel-drive.htm