Whats the difference between 4WD and AWD?

[npoe1]

Originally posted by: Demon-Xanth

Originally posted by: JulesMaximus
Clearly they aren't the same thing. Contrary to popular belief, it is possible to wreck a 4WD vehicle by skidding off the road.

They were called trees. Didn't matter how many wheels were being used to drive it, the car always lost.

A sequoia forest?

 

[marvdmartian]

Originally posted by: JulesMaximus

Originally posted by: marvdmartian
AWD good for pavement, and other improved surfaces. FWD good for on or off road (and for pulling everyone else out of the ditch when the roads get icy! LOL)

Funny, the vehicles I always saw in the ditch first when it snowed were the 4WD ones because their idiot drivers seem to think they're immune to the laws of physics.

Where I live, the last time it snowed (it's pretty infrequent), it was the front wheel drive types that ended up in the ditch......for exactly the same reason! :laugh:

 

[JulesMaximus]

Originally posted by: marvdmartian

Originally posted by: JulesMaximus

Originally posted by: marvdmartian
AWD good for pavement, and other improved surfaces. FWD good for on or off road (and for pulling everyone else out of the ditch when the roads get icy! LOL)

Funny, the vehicles I always saw in the ditch first when it snowed were the 4WD ones because their idiot drivers seem to think they're immune to the laws of physics.

Where I live, the last time it snowed (it's pretty infrequent), it was the front wheel drive types that ended up in the ditch......for exactly the same reason! :laugh:

This just in: It doesn't really matter what kind of car you own, if you have good tires (or snow tires), keep it in good operating condition and slow the fuck down when driving in adverse conditions you can drive through most anything mother nature throws at you.

No, brainwashed fucktards, you don't need a 4wd vehicle to get to the grocery store with 3" of snow covering the roads.

<--Captain Obvious at yer disposal.

 

[Throckmorton]

Originally posted by: Jumpem
AWD can be driven on dry pavement. this is useful in the winter when the roads go back and forth between snow covered, light snow, ice, slush, and dry pavement.

With a 4WD truck you are constantly putting it in and out of 4WD. With AWD you don't have to worry about it.

A lot of 4wd vehicles have a transfer case with a differential in the center. The NV242, which is used in some Cherokees and Humvees, has that feature. The NV231 in my Cherokee doesn't.

 

[Throckmorton]

Originally posted by: Vic
AWD originally stood for All-the-time 4-Wheel-Drive.

Usual agreement is that the biggest differences are that 4WD can be disengaged and has a transfer case or locking center differential (and vice versa, AWD cannot be disengaged and has a unlocked center diff). And it's because of the locked center diff that 4WD needs to be disengaged on dry pavement or having the front and rear wheels spin at always the same speed can cause wheel hop on turns. While AWD has a center diff allowing varying wheel speeds and torque distribution front and rear.

4x4 originally stood for 4 speeds to 4 wheels.

You sure 4x4 didn't originally stand for 4 wheels, 4 powered? My dad said a long time ago it stood for 4 doors, 4 wheels driven.

 

[Bignate603]

Originally posted by: Throckmorton

Originally posted by: Vic
AWD originally stood for All-the-time 4-Wheel-Drive.

Usual agreement is that the biggest differences are that 4WD can be disengaged and has a transfer case or locking center differential (and vice versa, AWD cannot be disengaged and has a unlocked center diff). And it's because of the locked center diff that 4WD needs to be disengaged on dry pavement or having the front and rear wheels spin at always the same speed can cause wheel hop on turns. While AWD has a center diff allowing varying wheel speeds and torque distribution front and rear.

4x4 originally stood for 4 speeds to 4 wheels.

Then real jeeps would have never been 4x4s
You sure 4x4 didn't originally stand for 4 wheels, 4 powered? My dad said a long time ago it stood for 4 doors, 4 wheels driven.

 

[Pacfanweb]

4wd splits power 50/50 to the front and rear.

AWD usually has most of the power to the rears, and a little to the front, but is capable of kicking more to the front if the rears start spinning.

In other words, it's worthless in any real slick situation compared to a real 4x4.

But good to have in rainy conditions.

 

[Nyati13]

Originally posted by: Pacfanweb
4wd splits power 50/50 to the front and rear.

AWD usually has most of the power to the rears, and a little to the front, but is capable of kicking more to the front if the rears start spinning.

In other words, it's worthless in any real slick situation compared to a real 4x4.

But good to have in rainy conditions.

The sports cars with AWD are usually rear biased, but the majority of car/SUV/wagon AWD is front biased.

I'm only familiar with Subaru systems, since that's what I drive. The manual AWD is 50/50 under normal conditions and can push up to 100% of torque to the axle with the most traction. The auto AWD is 50/50 in 1st and 2nd gear, then switches to 90/10 in the upper gears, and can push as much as 100% of torque to the axle with traction.
2009 model Subs also use the brakes to stop wheels that have been lifted off the ground, preventing the torque from being wasted on the no-traction wheel. Pretty slick set-up.

 

[Pacfanweb]

Originally posted by: Nyati13

Originally posted by: Pacfanweb
4wd splits power 50/50 to the front and rear.

AWD usually has most of the power to the rears, and a little to the front, but is capable of kicking more to the front if the rears start spinning.

In other words, it's worthless in any real slick situation compared to a real 4x4.

But good to have in rainy conditions.

The sports cars with AWD are usually rear biased, but the majority of car/SUV/wagon AWD is front biased.

I'm only familiar with Subaru systems, since that's what I drive. The manual AWD is 50/50 under normal conditions and can push up to 100% of torque to the axle with the most traction. The auto AWD is 50/50 in 1st and 2nd gear, then switches to 90/10 in the upper gears, and can push as much as 100% of torque to the axle with traction.
2009 model Subs also use the brakes to stop wheels that have been lifted off the ground, preventing the torque from being wasted on the no-traction wheel. Pretty slick set-up.

Yeah, and I should have written that I was talking about trucks and not AWD cars.

 

[dug777]

Quite simply, 4WD has two open or LS diffs or less (they can both be locked to actually physically drive four wheels constantly) delivering power to four wheels, AWD is anything else that delivers power to four wheels, and in its traditional sense uses three open or LS diffs.

 

[Throckmorton]

The NP242 transfer case, used in a lot of vehicles including the Humvee and many Jeeps has a center planetary diff that can be locked. I don't know about Australia, but the vast majority of offroad vehicles in the USA aren't even available with locking diffs. AFAIK, the only ones are the Wrangler JK, Toyota FJ, and Hummer H3. I can envision them being universal in Oz because if you get stranded in the Outback you could die.

 

[Pacfanweb]

Originally posted by: dug777
Quite simply, 4WD has two open or LS diffs or less (they can both be locked to actually physically drive four wheels constantly) delivering power to four wheels, AWD is anything else that delivers power to four wheels, and in its traditional sense uses three open or LS diffs.

Open and Limited Slip are not the same thing, as you probably know. On a slick surface, like snow, a limited slip WILL drive all the wheels...but it will allow slippage in turns or if one tire has a LOT more traction.

Very few trucks (1/2 ton, not larger trucks) ever came with a LSD in the front, so for the most part, no 4x4's were ever TRULY 4 wheel drive.

And if they didn't have a LSD in the rear, they were effectively a 2wd vehicle.

Lots of manufacturers are offering selectable lockers these days. Best of both worlds....turn it on, both wheels will turn, period. Turn it off, and most revert to limited slip. The Jeep's Rubicon package has included selectable lockers front and rear since about 2003, which is a big part of why it's the most capable factory 4x4 ever built.

Other lockers.........

There are aftermarket selectable lockers like ARB and Ox, which are either open or locked.

I chose ARB's for my Jeep I'm building....you really don't want a locker much in the snow (not that we have much around here, but we are close to the mountains). An LSD or open will drive much better. (unless you temporarily need the traction to pull a stuck vehicle or something like that, then a locker would be good)

I don't think any light-duty trucks come with ratcheting lockers like the Detroit, nor did they ever for the most part.
It's a true locker that engages with input from the pinion, and unlocks when you let off the gas...but has lots of popping and banging associated with it, especially around corners. It's been popular in racing for decades, and is bulletproof.

 

[Throckmorton]

Even with open diffs, a truck is 4WD. All wheels always get the same amount of torque, so when one wheel slips, they all get that miniscule torque. If they all have traction, they are evenly driven.

 

[Pacfanweb]

Originally posted by: Throckmorton
Even with open diffs, a truck is 4WD. All wheels always get the same amount of torque, so when one wheel slips, they all get that miniscule torque. If they all have traction, they are evenly driven.

I see your point, but technically that isn't correct. All wheels do not get the same amount of torque. Both DIFFERENTIALS get the same amount.....but if one wheel has traction and one doesn't, the one with traction is only going to use the small amount it takes to get the differential action to feed power to the wheel without traction.


Now if all 4 wheels have an equal amount of traction, and the truck is going absolutely straight which would prevent any differential action, then yes, there is equal power to all 4 wheels. And you could even get really technical with that and start looking to see if all tires had the same air pressure, etc, to totally eliminate the diff. action.

 

[Throckmorton]

Originally posted by: Pacfanweb

Originally posted by: Throckmorton
Even with open diffs, a truck is 4WD. All wheels always get the same amount of torque, so when one wheel slips, they all get that miniscule torque. If they all have traction, they are evenly driven.

I see your point, but technically that isn't correct. All wheels do not get the same amount of torque. Both DIFFERENTIALS get the same amount.....but if one wheel has traction and one doesn't, the one with traction is only going to use the small amount it takes to get the differential action to feed power to the wheel without traction.


Now if all 4 wheels have an equal amount of traction, and the truck is going absolutely straight which would prevent any differential action, then yes, there is equal power to all 4 wheels. And you could even get really technical with that and start looking to see if all tires had the same air pressure, etc, to totally eliminate the diff. action.

You misunderstood what I said. All 4 wheels do get the same torque, but when one wheel is slipping, they all get that zero torque (or near zero). And nearly zero load is on the engine, which is why it will rev up so easily.
In "AWD" systems where a slipping wheel brakes, that allows the rest of the wheels to get the same torque that the brake is applying.

When you turn a corner on dry pavement, all 4 wheels still get the same torque. It makes sense when you think of the spider gears as a seesaw. It's impossible for it to send more torque to the outside or inside. Power is a different story, because power is speed * force, so the outside wheels take more power

I didn't realize or even think about this stuff until I read this post

http://www.jeepforum.com/forum/showthread.php?t=130169

 

[Pacfanweb]

Ah, so you rock the Jeepforum, too? Got a Jeep?

 

[Throckmorton]

Yeah, a 1999 XJ http://farm4.static.flickr.com...95085_e6498a1baf_o.jpg
Planning to do 3.5" lift, slip yoke eliminator, and 32" tires.

I had a WJ with a 2" lift but I gave it to my dad (who helped me buy it anyway)

 

[Bignate603]

Originally posted by: Throckmorton
Yeah, a 1999 XJ http://farm4.static.flickr.com...428_b07a26ffa5.jpg?v=0
Planning to do 3.5" lift, slip yoke eliminator, and 32" tires.

I had a WJ with a 2" lift but I gave it to my dad (who gave helped me buy it anyway)

I've got two friends that have installed the Rubicon express 4.5" kit on their XJ's, it rides amazingly well.

 

[Pacfanweb]

Originally posted by: Throckmorton
Yeah, a 1999 XJ http://farm4.static.flickr.com...95085_e6498a1baf_o.jpg
Planning to do 3.5" lift, slip yoke eliminator, and 32" tires.

I had a WJ with a 2" lift but I gave it to my dad (who helped me buy it anyway)

Cool. I have a buddy who has one of those on 35's. He put a 9" Ford rear under it last year. Got amazing use out of the stock axles with not much problem, though.

I'm restoring/modifying my 1981 CJ-7. Sort of in a slow-down on it right now...but going to get back on it shortly.
This thread has lots of pics

 

[Throckmorton]

I'm probably going to go with the Rubicon Express 3.5" and a JB Conversions SYE http://www.jbconversions.com/p.../np231j_short_sye.html