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Old 04-29-2001, 06:56 PM   #1
Fubaru
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Post What's the difference between AWD and 4WD?

I really don't know!
Clue me in please
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Old 04-29-2001, 08:04 PM   #2
ninetalesnwf
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AWD has ajustable diffrentals
4WD is just straight 50/50 split

I think
i hate spelling
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Old 04-29-2001, 08:34 PM   #3
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From what I understand, the difference is this: With AWD, power is transferred to each wheel independantly. With 4WD, power is transferred to each set of wheels (front and back).
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Old 04-29-2001, 08:40 PM   #4
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Start here: www.eskimo.com/~eliot/awd.html It's a bit out of date but still a pretty good primer.
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Old 04-29-2001, 10:47 PM   #5
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With AWD there is a center differential which allows the front and rear differentials to spin at different speeds. 4WD sends power front and rear without allowing either to spin faster than the other. There are some systems that have a center differential and can operate in AWD mode with the ability to lock the center diff and operate in 4WD mode.
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Old 04-30-2001, 12:19 AM   #6
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I belive the technical difference between AWD and 4WD is the presence of a transfer case.
Old Explorer V8, no transfer case - AWD
Jeep WJ V8, Transfer case no 2wd - Full time 4wd (same with Land Cruisers)
Other Truck, Transfer case, no center diff, must use 2wd on pavement - Part time 4wd.

This has been discussed before. I'm not sure, but the older Subarus were confusing. Some 4wd, some awd, some fwd. What gives.
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Old 04-30-2001, 06:56 PM   #7
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Yes,

Check out http://www.eskimo.com/~eliot/awd.html for sure. Also some more good stuff (in terms of handling) is at http://www.rallycars.com/Cars/4wd_turbo_cars1.html

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Old 04-30-2001, 08:21 PM   #8
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You're telling me that the Eclipse/Talon/Laser have a transfer case?
Transfer case being the item that allows you to have 2hi/4hi/N/4lo?
On some there is no 2hi, just the 4wd.

So I can go rock crawling in an Eclipse. Cool.


I think you might be confused. My jeep has a center diff and it's 4wd. The only difference between the Jeep and WRX is that transfer case. Center diff doesn't matter for 4wd/awd. Center diff only matters for permanent/part-time 4wd because w/out the diff you can't run it on high-traction surfaces.

[This message has been edited by horatio102 (edited April 30, 2001).]
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Old 04-30-2001, 09:45 PM   #9
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horatio102, in DSM's it is called a transfer case. it's not a center diff by any means and it's not a conventional transfer case either.
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Old 04-30-2001, 11:09 PM   #10
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I have a factory shop manual for the DSM right in front of me that clearly says that it has a transfer case.
Visit this link to see a picture of it.
http://www.vfaq.com/mods/transfer-print.html

Basically it breaks down like this:
2WD: power is send to either the front or the rear wheels
AWD: power is send to both the front and the rear with differentiation between the two to provide for differing speeds experienced while driving on the street.
4WD: power is sent to both the front and rear with NO differentiation between the two. Completly locked i.e. not very streetable.
Conventional 4WD truck transfer cases that don't operate in AWD mode don't have a center differential.
BTW, the early ford explorer V8 had a transfer case.
http://www.truckworld.com/Sport-Util.../Explorer.html
(Edit: typo, addition)

[This message has been edited by WeRX (edited April 30, 2001).]
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Old 05-01-2001, 12:01 AM   #11
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There is certainly a fine line with a big grey area on both sides. The DSMs (Talon/Eclipse) have a transfer case and are AWD. The WRX has no transfer case but you could weld the center diff and have 4WD.
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Old 05-01-2001, 11:05 AM   #12
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It's my understanding that All 4wd cars need to have some sort of center differential which allows for different front and rear wheel speeds. This is needed for proper turning on regular roads.

The big difference between AWD and 4WD then is how they lock the center differential. YOU HAVE TO have someway of locking the center diff for a 4WD car, otherwise it would get stuck easier than a 2WD car.

With 4WD, there is some manual way (lever, button, ect...) of locking the center diff when needed for max traction or getting unstuck. With AWD, the locking system is built in, ussually in the form of a Limited Slip differential, that acts without driver interevention.
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Old 05-01-2001, 11:14 AM   #13
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It's a marketing gimmic.

4WD = AWD. In general, AWD implies that the vehicle has power to all 4 wheels all the time, while 4WD is used more to indicate that a Truck or stupid ugle vehicle (SUV) has the capability of AWD, but only when selected.

Modern AWD and 4WD all have some type of center diff, and some type of front and rear axles, but the basic princible is the same.

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Old 05-01-2001, 07:41 PM   #14
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I have owned 3 4WD trucks that had no center differential. If a 4WD vehicle doesn't power all four wheels onroad (AWD) there is no need for a center diff. Here's a diagram of a Dana 20 gear driven transfer case, only 2WD & 4WD hi/low modes, notice the lack of a center differential.

<IMG SRC="http://www.mailordercentral.com/broncograveyard/images/TRCTCASEDIAGRAM.JPG" border=0>
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Old 05-02-2001, 12:38 AM   #15
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Ok when I talk about a transfer case I'm talking about a multi-speed transfer case where there is driver input to select mode. The transfer case in the DSM and Explorer is nothing more than a housing for a center differential. You are correct. They do have one.

Strepto - How is it not a center diff in the DSM? Does it not allow the front and rear axles to turn at different rates?

Nebscoob - Most 4wd's don't have a locking center differential. Land Cruisers I think are one of the only equipped with one. Most 4wds don't have a center differential, at all.

WeRX - Even that article points out that the Explorer is awd. They state that the difference between awd/4wd is driver interaction with the 4wd system.


What's the difference between AWD and 4WD?
4WD has a high range, low range and possibly 2wd. The 4wd may or may not be safe to use on road. If it can be used on road, it's got a center differential. If not, it doesn't.
AWD has no low range, no 2wd mode, and can be used on pavement. It must have a center differential.
4x4 is a generic term that encompasses both 4WD and AWD.
Thank you for being picky enough to make me correct myself.


[This message has been edited by horatio102 (edited May 02, 2001).]

[This message has been edited by horatio102 (edited May 02, 2001).]
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Old 05-02-2001, 05:52 AM   #16
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My mistake, there are some 4wd which don't have a center diff, sure...

2 types of 4wd as I see it.

Those that drive all 4 wheels, using a center diff, and manually lock the diff as needed, AND.. those that function as 2wd until the 4WD system is manualy engaged, at which point the front and rear wheels are tied directly together with no center diff.

Subies are the same way, using the same methods, just with automatic 4wd lockup. (Making them AWD) The manual uses a LSD for the center diff, so it needs no manual locking, and the auto (new WRX is different, I know.) doesn't really have a diff, just an electrical lockup mechanism to tie the rear wheels to the front.

I think 4WD doesn't really mean that it has to have a low range. If I took the LSD out of my impreza and put in a manually lockable center diff, then it would be technically 4WD and not AWD, and yet it would have no low ranage, and drive all four wheels all the time. The difference is, as the artical says, driver intervention in the system.
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Old 05-02-2001, 05:51 PM   #17
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>the difference between awd/4wd is driver interaction with the 4wd system.
Not true, my GF has a new Explorer and in 2WD the tranfer case will automatically engage 4WD if it senses slip of the rear wheels. (Note: there is no center diff in this truck.)
>AWD has no low range, no 2wd mode, and can be used on pavement.
There are trucks with 2WD, AWD and 4hi/low modes available. So what's the difference between AWD and 4WD mode in these vehicles? Locking of the center diff. You can have AWD and 4WD on the same vehicle.
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Old 05-03-2001, 12:44 AM   #18
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Bah. Screw it. I'm getting bored with this conversation. You aren't going to convince me that the only difference between AWD and 4WD is a locking differential. I'm not going to convince you otherwise. There are so many variables. The Dodge and GM systems that offer 2hi\4hi\N\4lo\AWD aren't actually AWD. They're running 2wd until they need a boost from the front axle, and the GM at least uses an electric actuator to send torque to the front. If there is continuous slippage, it engages 4hi until traction is recovered. There is no center differential. It's a computer that takes over the manual engagement of 4wd for you. Back when that article was written there was either AWD or 2/4hi/4lo and that was that. One required intervention. Now there are so many variables it's impossible. In my book if it's a true 4wd, it's got a low range and some sort of manual interaction. Otherwise it's just a poser for those who will never venture off road.

I'm sick of this thread and I won't be replying anymore. It's like the debate between Coke and Pepsi. There is no right answer. I have no hard feelings towards you guys, I'm just sick of the discussion.

[This message has been edited by horatio102 (edited May 03, 2001).]
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Old 05-03-2001, 09:31 AM   #19
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AWD not having a lo-range only applies in the U.S. for now. European and Aussie 5-speed Subes (OB and Forester I think) come with a lo-range.
We might see it in the US depending what they put on the production ST-X and other future Subes.
Dennis
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Old 05-03-2001, 10:15 AM   #20
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Horatio, i agree that this thread has gotten old. Hard feelings?? Yeah right, we're all subbie friends. I think we can all agree on one thing, that we are all here to have fun and not to make enemies.
Have a good day!
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