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Old 02-22-2001, 01:38 PM   #1
garface
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I believe that 1st and 2nd are 50/50 splits, then 3rd and drive go to regular 90/10 which really isn't 90/10 supposedly, but that's another topic.
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Old 02-22-2001, 01:53 PM   #2
Keiho
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Understeer in the snow? Maybe you're driving too fast into the corner? Or you can always use the ebrake. That'll get your tail out in a jiffy. I always just lay on (gently) the throttle and the tail will will come around in the snow.

Oh yea, I have a MY00 with LSD and a Whiteline rear sway bar set at 20mm..even in the snow.
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Old 02-22-2001, 02:24 PM   #3
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Angry

christ, did everyone's brain fall out of their heads overnight or what? I can't count the errors in the "other" AWD discussion started by dcrawford and now this.

until the 2001 LL Bean and VDC Outbacks the 4EAT was 90/10, essentially the 10% just DRAG on the clutch pack. these H6 Outbacks brought to North America the new viscous torque distribution (VTD) 4EAT automatic, which has a default torque split of 45/55-- considerably less FWD.

the new WRX automatic has VTD as well, but it has not been publicly released yet if any of the other models besides the Outback H6s will get it. the WRX automatic's split is 45/55 just the same though.

*ALL* modern Subaru manual tranny vehicles sold in NAmerica have a 50/50 default torque split and it is a standard limited slip differential, incapable of biasing power to a driveshaft with more grip. It simply tries to lock them together-- it really will be near 50/50 all the stinking time.

Some Japanese MT models have a totally different type of center differential-- a planetary gearset-- instead of a viscous coupler. They can offer driver-adjustable split from 35/65 to 50/50 locked.

Are we done yet???
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Old 02-22-2001, 02:26 PM   #4
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Actually, it is a 90/10 split on the pre-WRX automatic Imprezas...with the new WRX VTD auto tranny, it is now 45/55...

Check this out for more info...
http://www.i-club.com/ubb-files/Foru...ML/001624.html

D. Neil Crawford
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Old 02-22-2001, 02:40 PM   #5
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Wait a minute here...the info I got was wrong? What in the world is going on here? I posted my question in order to learn what the differences are...got a ton of answers that explained a lot...and was happy with it. But now I am hearing that what was posted was incorrect?

This is insane! How in hell am I supposed to get a straight answer here???

ColinL...I PMed you...I am curious to hear your opinion on this matter.

D. Neil Crawford
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Old 02-22-2001, 03:14 PM   #6
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ColinL

I too would be interested in what factual errors you thought were made on the other thread...I don't know about you but I like coming here to discuss and learn about topics such as this. Please share your thoughts!
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Old 02-22-2001, 04:02 PM   #7
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Excuse me, dcrawford's topic is actually fine and full of useful info. I must have been thinking of another recent discussion. Sorry all... I either spend too much time here or I am imagining that suddenly many folks don't understand the Subaru AWD systems. (The only incorrect reply there is the 1st one from 10th warrior... and he no doubt knows a lot more about it now too.)

Nebscoob, your correction of the FAQ about the MT is particulary good.

Brucelee's reply here is incorrect, but obviously I got more than a bit carried away. I could edit it but I'll leave it as a humility reminder.
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Old 02-22-2001, 04:44 PM   #8
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Phew! I was about to go insane there... after finally getting the facts straight on the FHI vs STi ver. V struts...I thought I would tackle the whole AWD system stuff. And now...that "appears" to be taken care of as well!

D. Neil "done with the questions for today" Crawford
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Old 02-22-2001, 04:45 PM   #9
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Quote:
I must have been thinking of another recent discussion.
There were several of them...some of the myths:

1) Automatics do not start at a 90/10 bias. They start at a 45/55 bias. (Addressed above.)
2) The 4EAT can transfer 90% of the power upon launch to the rear wheels for a RWD setup. (Yeah, if you have that much power to need all that grip! With 165 horses I doubt it.)
3) The 4EAT is capable of better turn-in due to a higher level of adjustability. (Very debatable, and only applicable if you're on the gas anyway.)

Some of these stem from the misunderstanding that really, AWD doesn't help you that much unless you're pressing the gas. It's not a magic system to keep you from spinning out whenever you get in the car, unfortunately.

Fargo- understeer is correctable many ways. Sway bar, rear vs. front tire pressure, better suspension, pressing the brakes in the middle of the term (snap! "whoa...") I don't reccomend the last one!
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Old 02-22-2001, 05:10 PM   #10
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AARRRGGHHH!!!

Just to clarify...once again!

The NEW automatics start at 45/55...not the pre-WRX automatic Imprezas...they are 90/10.

The NEW automatics can change the power to 90 rear...but the pre-WRX automatic Impreza can only move it to 50/50

The pre-WRX automatic is a great system, but does not have the capabilities of the new WRX auto (I am just talking about Impreza's here)

D. Neil Crawford
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Old 02-22-2001, 05:59 PM   #11
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Ok, noone has even touched the actual question.
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Old 02-22-2001, 06:08 PM   #12
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Wink

Doh! Sorry about that! I just got so carried away in the definitions...

In theory...with an automatic tranny...you should be able to wire in a dial to manually adjust the split between front and rear.

I have never heard of anyone doing that...but I know an adjustable center diff is standard on the 22B (but let's not get into what IT has for AWD! ).

Anyway...I would suggest talking to Trey Cobb or Rallispec about that...I know both of them have tossed ideas about the AT tranny in the past...they may be able to give you some insight.

But what do I know? I am just an accountant.

D. Neil Crawford

PS: If you want to correct oversteer or understeer...I would suggest using other means than messing with the AWD...other means are much much cheaper! Damn, I am an accountant aren't I?
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Old 02-22-2001, 06:14 PM   #13
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Neil-

I was addressing the myths. One of those is that the current-gen auto starts at 45/55 instead of 90/10. Obviously, that's not the case.

As for the transfer of power to the rear...as I was aware it could transfer up to 90% of the power from front to rear. Of course, it would take MASSIVE power to make that happen.
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Old 02-22-2001, 06:40 PM   #14
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Quote:
Wait, how was I wrong? He drives a 2001 OBS.... So, doesn't he have VDC? That is what I was explaining.... Or do only the H6 legacys get the VDC?
Not even close! There is only one model of Subarus in US has VTD AWD system in US - Outback H-6 VDC. All others include Outback H-6 L.L.Bean only has old AWD systems. Impreza WRX will be the only other Subarus to use VTD system. Obviously, VTD system costs more and Subaru can't afford to put it into every Subaru cars.

BTW, according to Subaru, the VTD system does use planetary gear system in center diff.

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Old 02-22-2001, 10:35 PM   #15
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I have an MY00 auto without any sway bar mods, and if you practice for a little, you have no trouble getting sideways in the snow. If you go into the turn to first, obviously, unless you are on blizzaks, spikes, or other snow tire, you are just going to keep going straight. You have to go at a moderate speed into the turn, the press the throttle down 30% harder, and your back end will kick out for some nice drifts.
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Old 02-23-2001, 12:41 AM   #16
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Post 4EAT 50/50 question for Subie Techs

Has anyone modified their car with an auto tranny to use the 50/50 split in 2nd, 3rd, and OD? Like a poor man's center diff switch?

I'm really sick of the bad understeer making left turns in the snow with the 90/10 split. I use 1st a lot, but I have to shift to 2nd to soon. IMHO, after 20,000 cumulative miles in several Subaru's, 50/50 is far better than 90/10 on gravel and snow.

I don't need any get a 5spd jokes thanks

Mike

[This message has been edited by FargoRS (edited February 22, 2001).]
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Old 02-23-2001, 05:10 AM   #17
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Yikes Guys!!!!!!!

For the guys giving me the skinny on understeer, I'm up to speed...thanks I do use my parking brake sometimes when turning in snow. Also, I will get a bigger rear bar eventually, but it won't null out any understeer at low speeds, especially in snow.

And for the guys that are telling my I have 45/55 off the line....um, no! The front wheels slip until power transfers to the back wheels. Has a slip grab feeling...not really jerky, but noticable where the 50/50 mode doesn't. Just a personal observation.

So back to my question...to anyone who knows! Can you make the default split 50/50 in all gears on the 4EAT? It's not really a big deal, I'll live if I can't. But I heard someone mention this could be done.

Oh yeah, I don't have VTD, VDC, or an H6...just a good old 2.5L with a 4EAT

Thanks,

Mike


[This message has been edited by FargoRS (edited February 23, 2001).]
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Old 02-23-2001, 07:07 AM   #18
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I've never seen so much disinformation. Those who don't really know, and can't be bothered to buy a service manual should not offer their 'technical' expertise to people asking for help. I can answer your question at least about the SVX tranny, which is (other than some heavier duty stuff), is the same as the legacy and 2.5 rs transmissions up through '99. In '99 the solenoids changed. Anyway, there is a duty solenoid 'C' that controls the lockup amount. In first gear, the lockup is 50-50, AWD is engaged. At other speeds, the lockup is 90:10. The TCU uses the forward VSS (speed sensor), and the rear VSS to detect slip from front to back. When this occurs, the TCU alters a PWM signal to solenoid 'C' which introduces more lockup. This is completely electronic, and is not like a viscous (shearing force), or Torsen (torque sensing) differential. To find out more about the SVX tranny, go here:

<a href="http://my.voyager.net/tmclane/index.html" target="_blank">SVX FAQ</a>

Keep in mind that the euro/aussie/japanese spec trannies for SVX do NOT employ the electronic diff, but instead use a fixed 45:55 differential.
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Old 02-23-2001, 07:10 AM   #19
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Forgot to add, the easy answer is to unplug the wiring harness to Solenoid 'C'. Instant 50:50 lockup.
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Old 02-23-2001, 07:16 AM   #20
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Thanks svxtrem. Great info! And I agree with you on the disinformation, but I can steer around most of it

Mike
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Old 02-23-2001, 07:23 AM   #21
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Fargo - IIRC, there is someone with a 4EAT rally car (SCCA??) that has locked their split at 50/50. Maybe you could find it with a search.
Dennis
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Old 02-23-2001, 09:37 AM   #22
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Ok, now I have a couple of questions that are related...

1. How many different versions of the 4EAT are there? I was under the impression that they were all the same. If so, what are the differences?

2. Does staying in the 50-50 mode on the 4EAT cause any damage (overheating diff fluid, etc.)? I've heard that on the manual transmissions, running a non-50-50 torque split for too long will overheat the VC fluid and ruin your diff.

These questions may warrant a separate post, but I figured with all the AWD experts already here I might as well ask.
Thanks!
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Old 02-23-2001, 10:43 AM   #23
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The auto does not have a viscous center diff, instead, it is a multi-plate clutch, and it works just like the clutch in a manual transmission. When maximum pressure is applied, the clutch is 'let out' and directly couples the rear wheels to the tranny. Since the front is also coupled, the power is transmitted to both front and rear drive at the same time. This results in the 50:50 ratio. As the pressure is reduced, the clutch is allowed to 'slip' resulting in varying amounts of power to be applied to the rear, up to (according to the service manual) 95:5. At this point, the rear wheel drive is basically disengaged, the clutch is fully depressed. Note that all things being equal, no wear is occuring when the clutch is let out (FWD mode), or engaged 50:50. Therefore, it should not hurt to leave the clutch engaged. HOWEVER- when you make a turn, the front wheels and rear wheels will rotate at different speeds; with the clutch engaged, either the clutch will be forced to 'slip', or the tires will be forced to slip. If the clutch is forced to slip, you will definitely see wear and heat in the clutch pack.

svxtrem
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Old 02-23-2001, 10:45 AM   #24
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EDIT: Sorry svxtreme...didn't see your post before I posted. So I ended up making the exact same point..I'l leave it in though with this edit remark.

Look at A 4x4 truck with some kind of manual diff lock. The reason for the manual diff lock is so that it can be engaged when needed for max traction, but disabled for normal road driving. The reason it needs to be disabled is that for normal driving on pavement, while turning, the back wheels travel less of an arc than the fronts.

If the diff lock were engaged, then it makes it hard to steer, tires scrub and other nasty side effects that come from not being able to have that speed difference between the front and rears.

If the auto trans AWD system is enagaged fully at 50/50, then it would be like having a permantly locked diff, and have the same type of side effects, if it indeed is able to lock at 50/50. What I mean is, it could be that a hard turn at 50/50 on dry pavement would make the clutch slip rather than the wheels! What everhappens I think it would cause stuff to wear out faster than it should, be it tires or the AWD system.

60/40 or some other ratio might work though.

[This message has been edited by NebScoob (edited February 23, 2001).]
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Old 02-23-2001, 01:46 PM   #25
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Learn something new every day. Or somethings, in today's case. Thanks SVX.
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