Does the WRX have a limited slip differential?
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This is a discussion on Does the WRX have a limited slip differential? within the Transmission & AWD forums, part of the Tech & Modifying & General Repairs category; What is the differential setup on the WRX please? Limited slip in the rear? Thanks....

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    Does the WRX have a limited slip differential?

    What is the differential setup on the WRX please? Limited slip in the rear? Thanks.

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    He simply abides. SD_GR's Avatar
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    If it is a WRX and not an STi variant it has open front and middle diffs. It will have a limited slip rear if it is an earlier WRX, but not if it a later WRX.
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    I should have clarified WRX only. When did Subaru stop putting in limited slip for the rear year wise?

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    ^^correct.
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    Re: Does the WRX have a limited slip differential?

    Quote Originally Posted by SD_GR View Post
    If it is a WRX and not an STi variant it has open front and middle diffs. It will have a limited slip rear if it is an earlier WRX, but not if it a later WRX.
    Interesting. I would classify the viscous center coupling as "limited slip."

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    Quote Originally Posted by zax View Post
    Interesting. I would classify the viscous center coupling as "limited slip."

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    I think you are right, because if it were anywhere else I'd not have considered it open. You're right.
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    Not entirely true.... The 4EAT (auto transmissions) use a torsen (torque sensing) planetary gear center differential, which apparently can also be locked by a solenoid from the transmission controller
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    Does the WRX have a limited slip differential?

    I think those can be opened by pulling a fuse?
    Last edited by Sinister; 09-11-2012 at 08:54 PM.
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    It sounds like it... and open it's a 45/55 tq split apparently

    (sorry... edited your post instead of replying)
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    Quote Originally Posted by Sinister View Post
    Not entirely true.... The 4EAT (auto transmissions) use a torsen (torque sensing) planetary gear center differential, which apparently can also be locked by a solenoid from the transmission controller
    FALSE!

    Not really, just wanted to contradict you
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    Re: Does the WRX have a limited slip differential?

    Quote Originally Posted by SD_GR View Post
    I think those can be opened by pulling a fuse?
    Quote Originally Posted by Sinister View Post
    It sounds like it... and open it's a 45/55 tq split apparently

    (sorry... edited your post instead of replying)
    I'm confused here gents. To me, an "open" diff insinuates a simple pin and ring mechanism that distributes torque to either of two output shafts from a single input shaft. To add a limited slip mechanism to a differential suggests the addition of any device that disallows (or resists) a large torque bias between either output shaft (keeps torque evenly distributed). This can be accomplished with a viscous coupling, Torsen or any other torque sensing mechanical mechanism, clutch-type, Detroit locker, or any other exotic mechanism. Kevin you suggested the center diff on the 4EAT is a Torsen type. This is a mechanical locking mechanism that can evenly distribute torque in accordance to the torque bias ratio. If SD is indeed correct and the center LSD can be disabled with the pull of a fuse, I would suggest that the center LSD is a clutch type LSD similar to the DCCD. The planetary gearset is simply to achieve the uneven torque distribution under normal driving. FWIW the 5mt doesn't have a planetary gearset since the bias is 50/50 during normal operation.

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    Quote Originally Posted by zax View Post
    I'm confused here gents. To me, an "open" diff insinuates a simple pin and ring mechanism that distributes torque to either of two output shafts from a single input shaft. To add a limited slip mechanism to a differential suggests the addition of any device that disallows (or resists) a large torque bias between either output shaft (keeps torque evenly distributed). This can be accomplished with a viscous coupling, Torsen or any other torque sensing mechanical mechanism, clutch-type, Detroit locker, or any other exotic mechanism. Kevin you suggested the center diff on the 4EAT is a Torsen type. This is a mechanical locking mechanism that can evenly distribute torque in accordance to the torque bias ratio. If SD is indeed correct and the center LSD can be disabled with the pull of a fuse, I would suggest that the center LSD is a clutch type LSD similar to the DCCD. The planetary gearset is simply to achieve the uneven torque distribution under normal driving. FWIW the 5mt doesn't have a planetary gearset since the bias is 50/50 during normal operation.

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    Quote Originally Posted by zax View Post
    I'm confused here gents. To me, an "open" diff insinuates a simple pin and ring mechanism that distributes torque to either of two output shafts from a single input shaft. To add a limited slip mechanism to a differential suggests the addition of any device that disallows (or resists) a large torque bias between either output shaft (keeps torque evenly distributed). This can be accomplished with a viscous coupling, Torsen or any other torque sensing mechanical mechanism, clutch-type, Detroit locker, or any other exotic mechanism. Kevin you suggested the center diff on the 4EAT is a Torsen type. This is a mechanical locking mechanism that can evenly distribute torque in accordance to the torque bias ratio. If SD is indeed correct and the center LSD can be disabled with the pull of a fuse, I would suggest that the center LSD is a clutch type LSD similar to the DCCD. The planetary gearset is simply to achieve the uneven torque distribution under normal driving. FWIW the 5mt doesn't have a planetary gearset since the bias is 50/50 during normal operation.

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    I'll have to look into it again, but I believe the 4EAT uses a MPT (multi plate transfer) clutch as well as the planetary torsen center, and the vlsd in the rear. But I believe that the front is open. I cannot remember off the top of my noggin though
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    Just looked it up. Apparently the 4EAT is an Active AWD which uses an open front, planetary center at a 45/55 split, and a MPT in the tailshaft with a VLSD in the rear.

    Something else cool I found out... the 4EAT automatically shifts to 3rd gear during hard stops (ie ABS engagement) to prevent engine braking which causes unpredictability
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