AWD vs. 4WD - What's the Difference?

[ridged]

I know that our Ridges are classified as 4WD but, occasionally, I see people refer to them as AWD. Will someone please explain the difference, or point to a good explanation? Thanks!

[TheRidgester]

Originally Posted by ridged

I know that our Ridges are classified as 4WD but, occasionally, I see people refer to them as AWD. Will someone please explain the difference, or point to a good explanation? Thanks!

The Ridge is primarily front wheel drive.. that's why we have better economy like a mini van. Our AWD comes into play when our trucks sense slippage, and allow a percentage of our torque swing to the rear to allow traction. That is what I heard

[ridged]

Originally Posted by TheRidgester

The Ridge is primarily front wheel drive.. that's why we have better economy like a mini van. Our AWD comes into play when our trucks sense slippage, and allow a percentage of our torque swing to the rear to allow traction. That is what I heard

So are you implying that 4WD and AWD are synonymous?

[TheRidgester]

Originally Posted by ridged

So are you implying that 4WD and AWD are synonymous?

Heres something I found on the net to explain in more detail...The links go into more detail on subjects

What is the difference between
Four Wheel Drive (4WD)
and All Wheel Drive (AWD)?

see also the (incorrect) Consumer Guide definition


Full time four wheel drive (not to be confused with: part time 4WD ) is a system that powers all four wheels at all times. Each tire creates about 25% of the available torque when the ground is level with a consistant surface. Driver has a choice of a "4-high" (that's your every day setting) and "4-low".

When "4-low" is selected the wheels create substantially more torque (on a Grand Cherokee its 2.72 times more) than in "4-high" - at the same time the vehicle moves at substantially slower speeds (2.72 times slower on J GC).

Important: "4-low" does not create more traction - it creates more torque and that can be detrimental when traction is marginal. Slipping tires are more likely in "low" than in "high"!

The low setting is an advantage for drivers who need to tow and maneuver a heavy trailer etc. and for drivers who at one point or another may want to negotiate difficult off-road terrain, when more torque and/or slower speed is needed.


All wheel drive is a system that powers all four wheels of a vehicle at all times as well. Full time symmetric AWD would be the best term to be used. Difference to full time 4WD is that a "4-low" setting is not available in AWD cars. Due to the lack of "low range" AWD vehicles are much less capable in off-road settings than full time 4WD vehicles, but work perfectly well on-road.


Recently some new "automatic" AWD systems have emerged. Fancy names like "Real Time 4WD" are hiding the fact that they are essentially sophisticated 2WD systems. Automatic asymmetric AWD would be the best term for them. They are much less capable in off-road settings than full time AWD systems and inferior to full time 4WD. However, automatic asymetrical AWD is becoming more and more sophisticated and offers pretty much everything consumers expect for everyday (pavement) driving.
Here is how they work: During traction loss on the driven axle (could be front or rear) a fully automatic system (hydraulic, mechanical or electronic) routes torque to the axle with traction. This means you have to completely lose traction in 2WD on your driven axle first and then the other axle will take over and try to keep the car moving. So, for a moment you have 4WD (AWD). Doesn't mean much because only two wheels have traction. Once the primary driven axle regains traction and both axles rotate at the same speed again, the system reverts back to 2WD.



A frequent consumer complaint about some automatic AWD is, that all 4 tires need to be replaced even if only 1 or 2 are bad.

[TheRidgester]

Here's an article from tire rack... stresses how important it is for us to maintain air pressure in AWD vehicles...

The ability of four-wheel drive and all-wheel drive vehicles to divide the engine's horsepower between its four tires is especially useful on loose or slippery surfaces such as sand and dirt, as well as on wet, icy or snow-covered roads. However it's important to remember that in order to transfer this extra power, the four-wheel drive and all-wheel drive vehicle's driveline mechanically connects the tires so they work in unison.
Four-wheel drive and all-wheel drive vehicles are equipped with additional differentials and/or viscous couplings that are designed to allow momentary differences in wheel speeds when the vehicle turns a corner or temporarily spins a tire. However, if the differentials or viscous couplings are forced to operate 100% of the time because of mismatched tires, they will experience excessive heat and unwarranted wear until they fail.
This necessitates that four-wheel drive and all-wheel drive vehicles use tires that are very closely matched. This is because different diameter tires roll a different number of times each mile as a result of the variations in their circumferences. Tire diameter variations can be caused by accidentally using different sized tires, tires with different tread designs, tires made by different manufacturers, different inflation pressures or even tires worn to different tread depths.
As an example of different tire diameters resulting from tires worn to different tread depths, we'll compare two 225/45R17-sized tires, a new tire with its original tread depth of 10/32-inch and a second tire worn to 8/32-inch of remaining tread depth. The new 225/45R17-sized tire has a calculated diameter of 24.97", a circumference of 78.44" and will roll 835 times each mile. The same tire worn to 8/32-inch of remaining tread depth is calculated to be 1/8" shorter with a diameter of 24.84", have a circumference of 78.04" and will roll 839 times per mile. While the difference of 1/8" in overall diameter doesn't seem excessive, the resulting 4 revolutions per mile difference can place a continuous strain on the tires and vehicle's driveline. Obviously, the greater the difference in the tires' circumferences, the greater the resulting strain.
This makes maintaining the vehicle manufacturer's recommended tire inflation pressures and using "matched" tires on all wheel positions necessary procedures to reduce strain on the vehicle's driveline. Using "matched" tires means all four tires are the same brand, design and tread depth. Mixing tire brands, tread designs and tread depths may cause components in the vehicle's driveline to fail.
Mismatched tires or using improper inflation pressures for all-wheel drive and four-wheel drive vehicles can also result in immediate drivability problems. Some Control Trac equipped vehicles in 4Auto mode may exhibit a shutter on acceleration and/or a noise from the front driveline and transfer case while driving. Some all-wheel drive and four-wheel drive vehicles may exhibit axle windup or binding while driving. Some four-wheel drive vehicles (manual or electronic shift) with a two-wheel drive mode may refuse to shift "on the fly" into 4x4 Auto or 4x4 High at highway speeds.

[ridged]

Thanks for the info. I can now see why I was/am confused by the terminology.

[arteegee]

The Rl always launches driving all 4 and gradually moves more to the front.

[iROC]

I like to think of the Ridge's 4WD as "reality-based", i.e., it comes on when needed.

That said, the Ridge is not AWD, because it does have a low setting (VTM), and a rear locking differential. The Ridge is a 4WD system that works when needed, along with a "low" option. Just as an aside, there are many 4WD pick-ups out there, and for most the rear locking differential is an option and not standard.

[swampler]

Originally Posted by iROC

That said, the Ridge is not AWD, because it does have a low setting (VTM), and a rear locking differential.

Sorry, but the VTM lock is NOT a low range setting. It does not change the torque going to the wheels. It only locks the ratio from front to back. IMO, from reading the quotes posted previously, it is closer to AWD than 4WD.

[iROC]

Originally Posted by swampler

Sorry, but the VTM lock is NOT a low range setting. It does not change the torque going to the wheels. It only locks the ratio from front to back. IMO, from reading the quotes posted previously, it is closer to AWD than 4WD.

Thank you, Swampler, I stand corrected. I thought it was 4WD given the fact that the VTM could only be used in 1st or 2nd gears (reverse too) and that the rear differential locked. Truth be told, I may not understand the mechanics, but I'm glad it works the way it does.