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Old 09-23-2009, 12:15 PM   #1
96WRX
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Default WRX and STi Diff Question

I believe I know the answer, but just wanted to check and make sure, are all WRX and STi rear diff's LSD's?
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Old 09-23-2009, 01:16 PM   #2
Chadillac4454
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diff faq-http://forums.nasioc.com/forums/showthread.php?t=533787
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Old 09-23-2009, 04:43 PM   #3
Big-E
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Wrx = Vlsd
Sti = Mlsd
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Old 09-23-2009, 06:09 PM   #4
96WRX
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Quote:
Originally Posted by Chadillac4454 View Post
diff faq-http://forums.nasioc.com/forums/showthread.php?t=533787
Sorry, I don't see where this answers my question.
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Old 09-23-2009, 06:11 PM   #5
96WRX
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Quote:
Originally Posted by Big-E View Post
Wrx = Vlsd
Sti = Mlsd
I assuming the MLSD is Mechanical Limited Slip Diff, which is what I'm looking for.

I didn't realize that Subaru was still using the VLSD, I have a 3.900 out of a Turbo Legacy.
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Old 09-23-2009, 06:18 PM   #6
Chadillac4454
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What types of differentials come stock?

Viscous: Used as the center and rear differentials in the WRX/RS (08+ WRX has an open rear diff). Varies power applied between two axles via fluid dynamics and discs. This type of unit is filled with a silicone based fluid that becomes thicker as the difference in input shaft and output shaft speed increases, thereby increasing the viscosity of the fluid and the grip between the input and output discs, which do not actually touch each other.

Suretrac: Only available on the 2004 STi. Manufactured by AP Racing, this unit comes stock in the front differential of the 2004 STi. It is a mechanical type differential that employs a set of specially shaped teeth to intelligently transfer power, unlike the bevel gears that are used in conventional LSDs. Very similar in operation to the torsen type, though through different mechanical means.

Open differential: Used as the front differential in the WRX/RS. In a nutshell, it’s one wheel drive. The wheel with the least amount of traction will have majority (if not all) of the vehicle’s power applied to it.

DCCD: Short for Driver Controlled Center Differential. Used on the STi. Planetary center differential in conjunction with an electronically managed continuously variable transfer clutch. And as the name suggests, it allows the driver to control the torque bias of the center diff by a turn of the thumbwheel.

Torsen type differential: Used as the front (2005+) and rear differentials in the STi. Short for TORque SENsing differential. It’s worth mentioning that though Torsen is a brand name, it is the most commonly used name for this type of differential. This type of unit is also known as a helical or mechanical type. It uses gears to split power between two axles. Once one wheel is off the ground or slips, it in essence, becomes an open diff or exhibits limited traction based on the torque bias of the unit. It has the added drawback of weight. The additional torque required to rotate a heavier differential will require more energy, energy is heat, heat is friction, friction and heat are wasted energy. It requires more energy to drive and this can be shown on a chassis dynamometer if same car
is measured before and after the differential change. The other downside is that if the engine is quite powerful and extra special abuse is administered (high grip launches, donuts, etc.) they will explode. These broken gears will make their way through the case and can cause considerable damage. Keep this in perspective though, as very few cars exert this kind of power and those owners tend to understand what that power is capable of breaking.

Searching can answer a lot of questions...
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Old 09-23-2009, 07:02 PM   #7
96WRX
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Join Date: Dec 2002
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1996 WRX STi Type R
555 Blue

Default

Quote:
Originally Posted by Chadillac4454 View Post
What types of differentials come stock?

Viscous: Used as the center and rear differentials in the WRX/RS (08+ WRX has an open rear diff). Varies power applied between two axles via fluid dynamics and discs. This type of unit is filled with a silicone based fluid that becomes thicker as the difference in input shaft and output shaft speed increases, thereby increasing the viscosity of the fluid and the grip between the input and output discs, which do not actually touch each other.

Suretrac: Only available on the 2004 STi. Manufactured by AP Racing, this unit comes stock in the front differential of the 2004 STi. It is a mechanical type differential that employs a set of specially shaped teeth to intelligently transfer power, unlike the bevel gears that are used in conventional LSDs. Very similar in operation to the torsen type, though through different mechanical means.

Open differential: Used as the front differential in the WRX/RS. In a nutshell, itís one wheel drive. The wheel with the least amount of traction will have majority (if not all) of the vehicleís power applied to it.

DCCD: Short for Driver Controlled Center Differential. Used on the STi. Planetary center differential in conjunction with an electronically managed continuously variable transfer clutch. And as the name suggests, it allows the driver to control the torque bias of the center diff by a turn of the thumbwheel.

Torsen type differential: Used as the front (2005+) and rear differentials in the STi. Short for TORque SENsing differential. Itís worth mentioning that though Torsen is a brand name, it is the most commonly used name for this type of differential. This type of unit is also known as a helical or mechanical type. It uses gears to split power between two axles. Once one wheel is off the ground or slips, it in essence, becomes an open diff or exhibits limited traction based on the torque bias of the unit. It has the added drawback of weight. The additional torque required to rotate a heavier differential will require more energy, energy is heat, heat is friction, friction and heat are wasted energy. It requires more energy to drive and this can be shown on a chassis dynamometer if same car
is measured before and after the differential change. The other downside is that if the engine is quite powerful and extra special abuse is administered (high grip launches, donuts, etc.) they will explode. These broken gears will make their way through the case and can cause considerable damage. Keep this in perspective though, as very few cars exert this kind of power and those owners tend to understand what that power is capable of breaking.

Searching can answer a lot of questions...
And this is not confusing to you? One second they are talking about WRX/RS's then STi's, then front diffs, then DCCD. I guess what I was looking for was something that simply stated:

2002 to current rear diffs for WRX and STi's
2002 WRX VLSD
2003 WRX VLSD
2004 WRX VLSD, 2004 STi MLSD
2005 WRX VLSD, 2005 STi MLSD
2006 WRX VLSD, 2006 STi MLSD
2007 WRX VLSD, 2007 STi MLSD
2008 WRX Open, 2008 STi MLSD
2009 WRX Open, 2009 STi MLSD
2010 WRX Open, 2010 STi MLSD

Instead of bouncing around the subject.
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