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Old 12-09-2002, 02:02 PM   #1
Hurrikain
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Member#: 25351
Join Date: Sep 2002
Location: Aberdeen WA
Vehicle:
2002 WRX
WR Blue Pearl

Default 4EAT "center diff" Question

I know that the 2001/2002 4EAT doesnt have a center diff like the 5MT, but rather a clutch plate setup to steadily increase power to the rear diff. The 2003 model year is supposed to have a true center diff that runs 45.5% front 54.5% rear and vary more like the manuals center diff. Now I havent blown up my 5MT and hope that I dont, but if push comes to shove I am going to swap to a 4EAT(sponsors willing) and would rather have this capability. Now I dont know anything about the 4EAT, is that clutch pack "center diff" removable like the 5MT's? I am wondering if I could find a 4EAT and then upgrade that and send the whole deal to level 10. What are the other neccessary upgrades? prop shaft and rear diff correct? TIA

Aaron
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Old 12-09-2002, 02:23 PM   #2
ciper
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Its not based on year. All of the 4eat since 90 center diff function the same except for the WRX and the VDC. Ill refer to this new one as VTD.

The old design can run the center diff at 100% duty cycle and all the power is at the front wheels. The wear surfaces in the diff still touch slightly, so you cant put the FWD fuse in and use a 2wd dyno. If you cut the wire from the TCU to the diff the clutches would lock and you would get a constant 50-50. So basically the extremes are 50front and 50 rear to 100 front 0 Rear

In the VTD the extremes are more like 15frnt 85 rear and 85front 15 rear.

If you plan to get an auto the first mods I suggest are the modified TC and slightly increasing the value of the dropping resistor.
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Old 12-09-2002, 02:47 PM   #3
Foxbat
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'08 Tribeca, Brown

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Since the VTD system in Auto WRX is controled by TCU in 4EAT, it's not that easy to just drop in the VTD into your MT WRX without singnificant changes because for the TCU to operate the VTD correctly, it needs sensors from wheels, steering and other places to make correct judgement to throttle the VTD.
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Old 12-09-2002, 04:32 PM   #4
akoshy
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Wink Re: 4EAT "center diff" Question

Quote:
Originally posted by Hurrikain
I know that the 2001/2002 4EAT doesnt have a center diff like the 5MT, but rather a clutch plate setup to steadily increase power to the rear diff. The 2003 model year is supposed to have a true center diff that runs 45.5% front 54.5% rear and vary more like the manuals center diff
If you talking of the WRX 4EAT (2002+), then the center diff is an Electronically controlled true Dual planetary gear setup that operates hand-in-hand with hydraulic transfer clutches and the torque bias is 45% to the front and 55% to the rear in non-slip conditions. It can vary the amount of torque bias based on conditions/throttle position. Subaru calls this AWD system as VTD (Variable Torque distribution).

If you were talking of the non-WRX 4EAT, then it has hydraulic transfer clutches that transfers upto 50% of the power rearward when conditions demand that. The non-slip torque split is 90/10 Front/Rear.
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Old 12-09-2002, 05:35 PM   #5
Paisan
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1996-02 4EAT Non-VTD is 80/20 initial tourque split.

Here is a thread where I describe the various systems and what years they are in.

http://forums.nasioc.com/forums/show...hreadid=196455

-mike
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Old 12-09-2002, 09:33 PM   #6
Hurrikain
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Thank you alot for the info. The one that I was thinking of was the VTD. I didnt realise it was already in the 2002, I thought it was only a newer thing. SO IF I was to do an ESXesque swap there is alot more than just the auto ECU and the tranny. Hmmm choices choices.
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Old 12-10-2002, 01:36 AM   #7
RebelINS
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2005 Impreza WRX STi

Default

Are you sure that the default split is 20/80, I am almost positive that it is 10/90 like my mullet.

-Wes
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Old 12-10-2002, 09:30 AM   #8
Foxbat
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Quote:
Originally posted by RebelINS
Are you sure that the default split is 20/80, I am almost positive that it is 10/90 like my mullet.

-Wes
In the earlier days of 97 when I first got my 97 OBS, the word on the street was that Legacies have 90/10 split while Imprezas have 80/20 split. There was never any official confirmation about this. Now I hear 2001 or later is 60/40 split, at least that's how it listed in Subaru web sites outside US. Add to confusion, Subaru tends to give US cars special treatment. VTD equipped cars in JDM and Australia is 36/65 f/r while we get 45/55. Sounds like SOA thinks US drivers can not handle more power toward rear axle.
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Old 12-10-2002, 01:42 PM   #9
ciper
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AWD 946 Rio Red Jpn built

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Realize this talk of split amount is based on the coding of the TCU, hardware wise very few changes have been made to the transmission.
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Old 12-11-2002, 11:28 AM   #10
pdlindor
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2002 Impreza RS
2009 Forester Limited

Default 60/40 split?

I got this email from SOA a few months ago when I inquired about the auto torque split for the 2002's:

Quote:
Dear Mr. Lindorff:

Thank you for your inquiry. Yes, the numbers you state in your message are correct. But, these figures are only used as a starting point. They adjust continually based on the where the power is needed. For all of the available information on our various AWD systems, please visit the 'All-Wheel Drive System' section of Subaru.com.

Thanks for the opportunity to be of assistance. Best wishes!!

John J. Mergen
Subaru of America, Inc.
-----------------------------------------------------------
YOUR ORIGINAL MAIL:

Hello! I am curious as to what the Front/Rear power split is for
the 2002 Impreza line. I have heard that the AT RS is 60/40, the AT WRX
is 45/55, and the MT RS and WRX are both 50/50. Are these numbers
correct?

Thanks,
Paul Lindorff
Is this guy BSing me? Anyone have a 2nd source to confirm/deny the 60/40 split?

Thanks,
~Paul
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