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4WD v.s. AWD [question]

Discussion in 'Drivetrain' started by Jamezzy, Mar 27, 2011.

  1. Jamezzy

    Jamezzy Well-Known Member Donated!

    For the longest time I thought 4WD & AWD were the same. Just now am I realizing their differences.

    Okay so my parents have a BMW X5. Amazing vehicle. Would look great and be great for offroad use. I thought all 4wheels move so why is everyone bashing and saying it isn't for offroad use, like Jeeps and Hiluxes are. They've got X5's driving in the snow. They're all the same aren't they? 4 moving wheels? All got traction? Not exactly.

    So a BMW X5 with Xdrive is basically AWD with braking applied to the slipping tire to regain traction. People don't like to take it on the dirt and go 4 wheeling. Takes corners differently, suitable for on road use performance wise.
    A Jeep, Hilux, etc on the other hand is 4WD. Meaning that all 4 wheels are spinning continuously regardless of the when taking a corner all tires spin at the same speed. Correct?

    But then there's locking differentials. Now I know this is great use for Rock Crawlers and basically any Truck you want to take into unforgiving terrain because if your rear has got one tire in a ditch and one spinning in the air, you can lock the diff and will force both rear tires to spin and you get yourself out of that tight spot. And I guess this is a great upgrade to your 4WD system. But wait...I thought a 4WD system already had all 4 tires spinning continuously? What the hell? :banghead

    So a 4WD system has all 4 tires spinning and it still needs a locking diff? And this system is a part-time 4WD right?

    Or does this only apply to the AWD system in which you've got a diff splitting power to the tires that need it the most and the tires that don't, in which in the locking diff in slippery conditions you need power to all wheels?


    http://www.youtube.com/watch?v=nxx6D-Eg ... re=related :eek5
    I'm just confused. If you still need diff locks in a part-time 4WD system then what the hell, it's the same as a AWD configuration?

    You know its just that these car companies just abuse the names 4WD, AWD, 4x4, and its just confusing to know exactly what drivetrain setup it actually has. :colbert

    Also in rallying, especially our ST165 Celica, its partime 4WD right? No need for a locking diff since there are no deep ruts? Handles well in dirt.

    Also one last thing drive-train experts, is it possible to configure a vehicle with a 4WD system still being suitable to the dirt like beloved our ST165s, that, at a flip of a switch, lever, button etc that it can send power to the rear wheels only, basically into RWD mode? Consider money not a factor here. Surely something like this has been done before?

    All this while also having the option of toggling the locking diff manually.

    Thanks in advance.

    -Jamezzy
     
  2. Klue

    Klue Well-Known Member Donated!

    you have got most of it right.
    4wd- is full time power to every wheel, no out side control
    awd- is usually vehicles that are FWD then apply power to the rear as the front looses traction, IE toyota matrix xr
    awd + traction control - is like whats in your x5 where it applies brakes to lower wheel spin.

    differentials are used in both 4wd and awd. there are locking types and limited slip types.
    Locking types will lock the two wheels(ie rear) so they both get the same power, same wheel speed. Limited slip will allow a LIMITED slip of one wheel before sending power to the wheel with traction(slower one)
    Both these types of DIFFS can be used on 4wd or awd, some can be controlled inside the cabin, and adjusted
     
  3. Jamezzy

    Jamezzy Well-Known Member Donated!

    Interesting. So what if, you would need to have a car perform well on dirt and on-road (kinda like an all around car, that can adapt to the terrain, ie from dirt rally racing to asphalt grip racing) what would be the best option?
     
  4. jwagner162

    jwagner162 Well-Known Member Donated!

    ---hmmm.

    -4wd and awd are the same. its marketing.
    -the difference is full or part time. full time means all 4 wheels are powered all the time. part time means that the driver can switch into 4wd mode. the car will be rwd and then switched into 4wd for off road use (on these vehicles you cant just drive around all the time in 4wd, youll destroy it).

    -as far as diff's. wikipedia it as they may have a nice diagram.
    ill try a quick expl. as a car takes a turn the outside wheels are spinning faster than the inside ones (they travel a longer distance). so your driveline has to have a way to compensate...a diff. the issue that arises is that because of the design power naturally travels to the wheel with the least traction (e.g. the 1 wheel burn out). introduce the "locker". they are a bunch of different types, but they all serve the same function. to evenly disrubute power to both wheels when slipage is detected.
    -awd you need to have 3 diffs. front, rear, and center. the center will compensate for speed differences between the front and rear axles, and is generally housed in the transfer case. your choice of locker is generally based on type of use or personal preference.

    -my land cruiser has no locking diffs. but does have both tracion control and stability control. so the computer can either brake a specific wheel or add power to it. my truck wont allow me to do donughts but it can paw up damn near anything. i get better tracion like this than fully locked jeeps. basically if your fully locked you can burn all 4 tires at the same time (on dirt).
    -so an x5 is likely the same, 4wd with traction control. the "not really for offroad" bit comes from the fact that it has a "lighter" drive train. its 4wd so you get great traction in snow, light off road, ect. but if you go do something nutty with it youll likley break an axle or other driveline component.

    -edit. i actually do have an electrionically controled (just means i have a button to actuate) center diff lock. so if i need more traction i can lock the center diff. this is a very low speed only thing as it generates a ton of heat. not even supposed to drive on asphualt with it locked.
     
  5. Klue

    Klue Well-Known Member Donated!

    4wd and AWD are not the same. 4wd is full time, and awd is partime. thats the difference.

    You want a 4wd vehicle for off road/performance. You want awd for on road/adverse weather
     
  6. Jamezzy

    Jamezzy Well-Known Member Donated!


    Lol you and Klue are kinda saying 2 different things! hmmmmmmm

    Wikipedia although puts 4WD and AWD into 2 different categories at one point, then they mix it up saying they're the same, confusing. But from what I've read on wikipedia, is that basically part-time 4WD is the real deal and Full-Time AWD is a watered down version?

    So do our 165s have an option to switch between modes RWD>4WD? I think someone mentioned it in specific models and years.

    Regarding the land cruiser, there are some vehicles that have a front locker and rear locker for maximum climbing ability. This video helps clarify me of my questions but still the people in the comments are also talking about 4WD and AWD lol. According to wikipedia, they are wrong? Anyway here is the video

    http://www.youtube.com/watch?v=RcRBYpcc ... re=related
    Interesting stuff.

    And for a more in depth showing moving parts and a demonstration. Awesome.
    http://www.youtube.com/watch?v=6E8LBoWa ... re=related

    So the X5 isn't for heavy offroad use to due to the light drivetrain? I've seen some videos of an X5 going up hill. Looked like it was surely gonna clear the hill with how fast it was going and then one of the tires lifted up and it shows that its got no locker, Although its got some 4 wheel power confusing because a jeep can probably clear it right? This raises the question as to which drivetrain is real 4WD and which is just computer controlled and light off road. :help Confusing lol


    Here the vid of the X5. Its only 15 seconds long.
    http://www.youtube.com/watch?v=vr2LCfl52_A
     
  7. jwagner162

    jwagner162 Well-Known Member Donated!

    -negative ghost rider.
    -my l.c. is AWD. all wheel all the time. no option to switch out. 4x4 is the same. its marketing. really.

    -alot of trucks (4x4) run rwd because of the lower gearing and heavier drive train in 4wd mode. also better mpgs.
    -i will say the teminoligy between US and OZ may differ but this is the common usage in the US.
    -e.g. here a wrx is awd. all wheel all the time. no 2wd mode. an f350 is a 4x4 (optional) meaning it would run rwd unless 4x4 mode is selected then you could consider it awd. so really the same as they all have 4w drive lines.

    -regarding the cruiser and other 4x4's. a diff can be swaped out to a locking type or different ratios fairly easily. but unless your really into heavy 4 wheeling there really not neccisary. there are tons of people who have dedicated 4x4's that they trailer out to the woods and are extremly capable.

    -in regarads to the x5 ect. i have a 100 series landcruiser (00') its considered a heavy/medium off road vehicle because it has an independant front suspension and a solid rear axle. the earlier (80 series) cruisers are considered heavy duty (you can go out jump it, roll it, drive it, in the river ect. and youll be able to drive home) because they have solid front and rear axles. this means my weakest link is the front cv joints that the earlier models dont have. but i have a way better on-road ride, and cupholders, and heated seats, and wood, ect. :hehe. if you look at something like a ford escape or probably an x5 it has 4wheel independant suspension. meaning you have a cv at each wheel. this puts you into the light duty class, excellent on-road ride, light duty off-road (such as driving on dirt roads, snow, ect) these type vehicles are NOT made to go out to say an orv park and try to out climb jeeps. (youll break a cv or something else)
     
  8. Jamezzy

    Jamezzy Well-Known Member Donated!

    @jwagner162
    I see. Although some vehicles can be switched from RWD to 4WD which I think is a great idea, saves gas and you can go drifting(car) and 4 wheeling(truck) despite the optional RWD to 4WD they ARE the same correct? And a 4X4 is just as capable as a permanent 4WD? So the only difference is how solid the drivetrain and suspension set up is.

    So a BMW X5s AWD is the same as many others. So if i go out and modify my X5's axels and CV boots, give it independent suspension and solid rear axel I'm good to go, not to mention add in a locker and other features that a heavy duty use 4X4 has?
     
  9. jwagner162

    jwagner162 Well-Known Member Donated!

    yes and no. being able to switch from rwd to 4wd is really the original setup, and started on trucks. its because of the heavy driveline and gearing within the transaxle. you couldnt just drive around in 4wd beacause youd kill the transaxle at high speed. youd just drive around in rwd till you hit a place you needed it, stop, switch to 4wd, get out, lock the front hubs, and away you go. once back on pavement youd switch it back.

    -i would venture to guess that the st165 is probably one of the first awd cars that was mass produced. while trucks have had this capability for a long time (ww2 i think). and also remember our 162s are the first fwd celicas. every thing was rwd up till around that time (like since the begining of cars). its really quite an achievment to combine the transmission and transaxle and shoehorn it into a car (this system is much much "lighter"). the transaxle on my truck is as big as the tranny on one of my celicas. although my truck has alot more capability.

    -so something like an escape, pilot, rav4, ect are really just lighter awd "car" type systems. which is great for 95% of people that feel they need awd for the occasional ski trip, ect. plus people are willing to shell out the extra cash for the added security. (again with the marketing). something more like my truck or something larger is made to actually go "off-road" like i can make my own road and probably wont get stuck as long as im not stupid. though an x5 and such may have a "heavier" drivetrain, you biggest limiter will be the tires.
     
  10. Klue

    Klue Well-Known Member Donated!

    4WD is constant AWD which is not selectable.
    4wd cars: Celica gt4, Talon 4wd, Rav4(old one)
    AWD cars: G35X, NEW rav 4, is250 AWD, matrix XR

    its just confusing be cause is similar
     
  11. Thaifighter

    Thaifighter Well-Known Member

    Hm that explains why most people don't go offroad with Skyline GTR's... lol
     
  12. Jamezzy

    Jamezzy Well-Known Member Donated!

    I would. On Gran Turismo
     
  13. Mafix

    Mafix Owner Staff Member Administrator Donated!

    the difference is in whether it's a car chassis or truck chassis
    then it's whether it's mechanical or electronic

    in cars (i honestly have yet to find a difference)
    awd = all the time
    4wd = all the time

    in trucks
    awd = all the time
    4wd = selectable

    now the diffs and electronics can pattern that however it's needed and varies greatly.
     
  14. Jamezzy

    Jamezzy Well-Known Member Donated!

    Like you said whether or not it's electronic or mechanical, I think it's the biggest difference.

    For the RAV4 there is a button that can pressed and switch on the 4WD/AWD, but only at a certain speed (I believe it's 25mph?). The RAV4's system also engages when there is some slipping in the tires in snowing roads etc.
    That one is clearly electronic.

    Then there are the almighty 4 wheel mechanical systems, which I prefer!
     
  15. jwagner162

    jwagner162 Well-Known Member Donated!

    -im betting the ravs system is a type of traction control and not an engagement of the 4wd system. in general most 4wd systems need to be engaged at low or no speed, thou there are "on the fly" systems. if it randomly engaged it would quickly destroy itself.

    -iirc theres really no benifit of elect vs. mech. just interface.

    -again 4wd and Awd is REALLY marketing. all vehicles capable of of it MUST carry the same basic components. front, rear, center diff's and a transaxle. no ifs ands or buts. a vehicle that is 2wd with selectable 4wd is setup this way so your mpg's and drivability dont suffer. things like axle selection (solid vs. independant) are picked by the manufacturer based on desired suspension setup and rugedness. e.g. something like a ford escape...4 wheel independant....gets relativly good mpgs, will see the occasional snowy road on a ski trip and maybe a scenic dirt road on the way to a hike. but would quickly break with heavy of road use. were something like a big dodge or ford (solid front and rear axle) is made to hit logging roads at 60mph, pull a tractor out of a ditch in the snow, and you already knew your mileage would be sh*t when you bought one. you could call either one whatever you want, as they have the same basic systems.
     
  16. Stig

    Stig ST162 Guru Donated!

    My understanding is technical, it has nothing to do with electronics
    Traction control is being built into all boxes nowdays

    AWD - All wheels driven by a conventional 5/6 speed gearbox

    4x4 - 1) Has the ability to engage/disengage wheels,
    also has 2) a low range gearbox for situations a conventional 1st gear won't cope.

    AWD vehicles typically have better grip than 2wd but cannot compete with 4x4,
    ie towing a boat through a desert, in fact most will bog on their own,
    they also have higer fuel consumpion and maintenance costs

    When your 4x4 is stuck, who do you call?
    A) A tractor - and it's 2wd
    Food for thought? Torque + light weight, low gearing and huge tyres
     
  17. Mafix

    Mafix Owner Staff Member Administrator Donated!

    perhaps that is the key difference is the low and high gear selector found in 4wd systems. i've never seen an AWD with that ability.
     
  18. ST185GT

    ST185GT Member

    in my opinion, i believe the term AWD is the best way for marketing purposes for car manufactures. You hear it all the time in commercials. Hearing AWD has a special appeal, instead of hearing 4wd etc, you know what i mean,
     
  19. Stig

    Stig ST162 Guru Donated!

    No, I got the info from a car salesman
    It's how they differentiate between AWD and 4x4
     
  20. fernandocelica

    fernandocelica Well-Known Member Donated!

    they are different otherwise they would name them the same 4x4 or AWD for me 4x4 can handle offroad water river's etc alot higher as well and never seen 4x4 riding with it engaged on the street diff gear's won't handle it .now on AWD car's it's what we call 4wheel drive car's made for dirt and for normal road subaru is an example of one and I still say AWD is way to go
     

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