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Guest Message by DevFuse
 

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need 100% on how awd works on auto legacy


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7 replies to this topic

#1 machine

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Posted 10 November 2005 - 01:47 PM

as some of you know i have a broken front axel .
the back drive it fine (i had to drive it 5 min to the shop ) and once i hit about 40 to 50 mph the rears would shut of and the front axel of course just spins and the speedo goes up


thisis not how i though subaru did there systems . if it shuts of completly after that speed its kinda useless for me as a awd system . unless theres somthign missing


and im putting the new axel in tonight


so do we know exactly how the awd system work in a 95 2.2 auto awd

thanks guys

#2 friendly_jacek

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Posted 10 November 2005 - 02:00 PM

I'm not entirely sure but what is probably happening that over that speed there is enough road and wind resistance that the AWD cluches start to slip and spin increasing your engine (and front diff) rotations. At most, the clutches can only transfer 50% of torque and not 100%.
Nobody claimes that AWD is superior to 4x4 in extreme conditions! It is better in avarage driving conditions and yours is not.

#3 machine

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Posted 10 November 2005 - 02:14 PM

yes i understand that and i can tell by driving it it only has limitied power to the rear . but it completly shuts off . much like the crv . over 80kmh the rears are of no use .

#4 zyewdall

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Posted 10 November 2005 - 04:35 PM

yes i understand that and i can tell by driving it it only has limitied power to the rear . but it completly shuts off . much like the crv . over 80kmh the rears are of no use .


That does sound odd that it shuts completely off. But, why do you need AWD at that speed anyway? (after you get the axle fixed, that is). If the road surface is so slippery that you need awd to get to faster than 50mph, you probalby don't want to be going over 50mph anyway, do you?

#5 nipper

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Posted 10 November 2005 - 04:41 PM

as some of you know i have a broken front axel .
the back drive it fine (i had to drive it 5 min to the shop ) and once i hit about 40 to 50 mph the rears would shut of and the front axel of course just spins and the speedo goes up


thisis not how i though subaru did there systems . if it shuts of completly after that speed its kinda useless for me as a awd system . unless theres somthign missing


and im putting the new axel in tonight


so do we know exactly how the awd system work in a 95 2.2 auto awd

thanks guys


you need to know how differentials work.:banghead: a differntial is a mechnaical computer. It divieds power between two wheels at a 2:1 ratio. This allows cars to turn and have the wjeels rotating at differnt speeds. You have two differentials. There is a center clutch pack that is not a differential in the pure form. but acts like one. A computer cycles a solemoid to apply up to a 50/50 torque split frt and rear. You are abusing the car by driving at 50mph with a broken axle. THe car is sensing too great a differnce between front and rear axle speeds at 30mph. The clucth pack is in full luckup trying to make the car go, and sensing it is still having a dramatic miss match in forces, is reducing the rear to 10% ro protect itself and the driver.
In old fasbioned manual 4wd they advize NOT to go over 50mp on dry pavement for the same reason. Subaru i imagine ahs this written in the puter for the same reason.
When you have one wheel (one since the axle is broken) spinning at 50mph the inside of the differentila is spinniung at 25mph. The rear differnetial is spinning at 40mph so thats a HUGE differnce of 25mph netween frnt and rear of the car inside the transmission. This is speed getting fed back INTO the transmission, not the way it should normally flow. To save the car from destroying itself it shuts off the rwd untill numbers make the computer happy.
The cars is operating as it should. Lets hope you didnt fry the transmission.

#6 jamal

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Posted 10 November 2005 - 04:49 PM

There are four or five endwrech articles that explain it pretty well, so check out that site, in the meantime I'll give a little summary: There isn't "on" or "off." The system is always splitting power front to back at a ratio between 90-10 and 50-50. As the front and rear differentials are both open, on a slippery surface you would only be able to spin one front and one rear wheels. Without another front axle there is no way for the front differential to transfer power to the ground.

The center differential on Subarus is a strange device seemingly filled with magic (especially those in autos). MT uses some sort of a limited slip differential and a viscous coupling and is purely mechanical (aside from DCCD), whereas the autos use a set of computer controlled clutch packs.

When you start out is that the center diff sends enough power to the rear wheels to get you moving. As the speed increases, I'm going to assume that the amount of power transferred to the rear decreases and the system gets a little less sensitive. This would make the car a little more efficient, and prevent any binding between the front and rear at higher speeds. In addition to that, you might be overheating the center diff, and it's refusing to transfer power in order to save itself.

Hopefully I'm not talking out of my rump roast completely.

#7 machine

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Posted 10 November 2005 - 05:22 PM

thanks guys it all makes sence . i just was under the impression that it was a 60 40 split all the time ( as the local dealer explained to me lol the dink )

and you right that over 50mph i don ttecnically need it bu what if i hit a big snow drift while on the hiway . but ive been fine in fwd so the awd will be a bonus .



i know how differentials work , im just new on the way subaru does there systems as there is many different ways to do it .

thanks for the replies ,

#8 machine

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Posted 11 November 2005 - 11:58 PM

well just a quick update , axel swap went good and took about an hour to do .

car runs great and im very suprised how smooth these cars are .noe it just needs to be a bit faster lol

thanks for all the help




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