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all wheel in reverse???


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15 replies to this topic

#1 Vfrazz

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Posted 21 June 2005 - 08:49 PM

I pulled down a rutted track with my 2002 Impreza Outback automatic to do some fishing. As I was backing out at the end of the afternoon, one wheel began to spin on a rock on the path (front passenger, I think). I waited for the other wheels to kick in and pull me along, but no-go. I stepped on the gas and the wheels spun faster--to the point of smelling rubber. At that point, I did the old two wheel thing--pulled forward, did a little run backward, and out we came. So...doesn't all wheel drive function in reverse?????

#2 thingol

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Posted 21 June 2005 - 09:38 PM

Yes, it does function in reverse, but since you have an automatic, by default 90% of the torque is up front, and it only transfers when it detects you slipping in the front. Now, you were clearly slipping, so it could have been that the other wheels were simply too stuck, and were not able to overcome the terrain, and your effectively open differentials then sent all the power to the free wheel. As much as I wish it was, AWD is not locked like a good 4WD system, so you can get it so stuck that you only spin one wheel (excepting if you have LSDs, or whatnot, and it would still theoretically be possible with LSDs as well).

#3 All_talk

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Posted 21 June 2005 - 10:59 PM

The 4EAT doesn't have a center diff, it uses a clutch pack to transfer power to the back wheels, since its electroniclly controlled it could be designed to function differently in reverse, I'm not sure about that. But if it was locked in you would have to be spinning one front and one rear wheel (open diffs), is it possible that was the case? You can check is operation in the gravel... I open the door and look at the back wheel, punch it, the front wheel should spin momentarily then the back will catch. I've never tried it in reverse but I can if you would like.

Gary

#4 EYE_WHY

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Posted 22 June 2005 - 12:05 AM

Speaking of power splits between front and rear and all that jazz, anyone know what the split is for a 94 Loyale MT SR? Just curious.

#5 All_talk

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Posted 22 June 2005 - 12:41 AM

Well I went out and ripped up the driveway a bit... mine works the same forword and back.

Speaking of power splits between front and rear and all that jazz, anyone know what the split is for a 94 Loyale MT SR? Just curious.


Locked in 50/50, no diff or clutch.

Gary

#6 Vfrazz

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Posted 22 June 2005 - 07:29 AM

Yes, it does function in reverse, but since you have an automatic, by default 90% of the torque is up front, and it only transfers when it detects you slipping in the front. Now, you were clearly slipping, so it could have been that the other wheels were simply too stuck, and were not able to overcome the terrain, and your effectively open differentials then sent all the power to the free wheel. As much as I wish it was, AWD is not locked like a good 4WD system, so you can get it so stuck that you only spin one wheel (excepting if you have LSDs, or whatnot, and it would still theoretically be possible with LSDs as well).


I think this is the answer, thanks...and now I remember the feeling of being decieved when, after I bought the car (new), I discovered that the transfer setup was only 10% for automatic, while much more for manual transmission...10% transfer, this is all wheel drive? Thanks to all who wrote in, and glad that a couple of others were able to piggyback their own questions...

#7 thingol

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Posted 22 June 2005 - 09:49 AM

I think this is the answer, thanks...and now I remember the feeling of being decieved when, after I bought the car (new), I discovered that the transfer setup was only 10% for automatic, while much more for manual transmission...10% transfer, this is all wheel drive? Thanks to all who wrote in, and glad that a couple of others were able to piggyback their own questions...



Actually, as I understand it, the clutch pack can transfer power up to 50-50, front rear, but it is normally 90-10 front rear for better gas mileage. This means you actually get up to 40% transfer. However, I am used to the manual system (which I have in all my roos), which is 50/50 front rear until slippage occures, b/c of the viscous center coupling.

#8 Andyjo

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Posted 22 June 2005 - 10:40 AM

Whenever i get stuck like that in my impreza, it's usually a very careful game of.. how much i can press the brakes and gas at the same time, and sort of alternate between them to 'fool' the AWD system.

#9 Tbird Man

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Posted 22 June 2005 - 10:06 PM

yes, the 90/10 myth has been busted, the split varies as you drive depending on demand. and in 1st on the shifter it is 50/50, this came from someone who tapped into the signel line to the diff with a sillyscope and drove around testing it. and my personal exp getting the front wheels on ice and punching it, didn't feel like 10%. as for reverse, it is possible they coped out and made it default to 90/10 in reverse.

#10 Zefy

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Posted 24 June 2005 - 01:16 AM

i have had this happen to me as well... front wheel on ice and the car didn't move at first... stopped for a moment then backed up again and it worked...

this is an MT in an 01 Legacy...

there was no problem... but i was surprised when a little patch of ice stopped me from moving...

#11 Andyjo

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Posted 24 June 2005 - 03:07 PM

Is there any way to alter the split?! that would be awesome....

#12 scoobyclimbs

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Posted 29 June 2005 - 04:32 AM

wire in a toggle switch to overide the Duty C solenoid (4eat) this will lock up the rear! I plan on doing this...It has been done successfully!

I do have a rear LSD so that helps ! Usually the only time I get stuck is highcentered in deep snow! I need more lift!

#13 LosDiosDeVerde86

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Posted 29 June 2005 - 10:02 AM

Actually, as I understand it, the clutch pack can transfer power up to 50-50, front rear, but it is normally 90-10 front rear for better gas mileage. This means you actually get up to 40% transfer. However, I am used to the manual system (which I have in all my roos), which is 50/50 front rear until slippage occures, b/c of the viscous center coupling.


that's how i understand it

#14 iluvdrt

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Posted 04 July 2005 - 12:28 PM

I thought that was only on a manual tranny you could get the 50/50 split.

The automagics use a viscous coupling limited slip system, that when under extreme situations....slips and doesnt provide any real traction.....I think.

#15 All_talk

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Posted 05 July 2005 - 02:03 AM

I thought that was only on a manual tranny you could get the 50/50 split.

The automagics use a viscous coupling limited slip system, that when under extreme situations....slips and doesnt provide any real traction.....I think.


No VC in the 4EAT, just a hyd clutch pack controlled by the TCU by varying the duty cycle to "Solenoid C". The front is driven directly, with only power transfer to the rear going through the clutch pack.

Posted Image

More pics inside the EJ 4EAT here:
http://photobucket.c...lk/Subaru/4EAT/

Yes, you can overpower the clutch pack, but you can overpower the VC in the 5MT aswell.

#16 iluvdrt

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Posted 05 July 2005 - 11:56 PM

Ohh, OK. Thanks for clearing that up, and the pics were nice too.




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