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STi swapped SF5, WTF?
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Discussion Starter · #1 ·
I am thinking of upgrading my front diff to an OBX LSD as they are a nice budget upgrade that seems to work quite well for Subarus. My question is whether or not the JDM Mechanical LSD would be worth the money to upgrade to and a better match for that front diff the the USDM Viscous LSD that is in my car now. I know there are better ones out there like the Cusco or Quaife rears but I am trying to stay on a budget if I can.
p.s - The car is mainly street driven with some fun backroad trips every now and then. Might look into auto-x in the future but not currently participating.
 

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05 OBP STi
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i have heard good things about OBX front diffs, but they require replacing some parts to make them reliable. right out of the box they're crap, but replacing $32 worth of parts makes them great apparently. I plan on getting one at some point. Cant go wrong for the price.

heres a link on rebuilding it and what to replace. he even sells the parts.
http://rbryant.freeshell.org/obx_washers

edit: i guess is missed your question, lol. from what ive read, the viscous rear lsd is better than the mechanical, sti's come with rear viscous lsd and mechanical front since v5. there is detailed info on here about it, but you kinda have to dig. i cant recall any specific links, sorry.
 

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99 Aspen White Coupe
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I'm not sure, but I think that's incorrect. STi has generally used mechanical rear diffs as well, and most everyone agrees that mechanical is better. Hopefully someone with more knowledge than me will jump in to confirm.
 

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overdeveloped beater
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My OBX front diff is still working just fine despite not doing anything to it besides pressing the bearings on and installing it. That doesn't mean that if a buyer is anal about improbable issues, they shouldn't worry about it.

A rear mechanical is the way to go with a front helical LSD. JDM is fine, once you get the right axles.
 

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MY99 GF4 EJ227 JDM 6spd
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If you really want the rear LSD to work well, get the REAL stuff, KAAZ.

I don't know if you're read a few of my posts..... The STOCK OEM clutch type LSD is decent. However it doesn't have the good initial lock up and sesativity that I want when I'm performing my driving. I would like the inside rear to not SPIN when I'm starting a donut with just giving it throttle. I would have to clutch KICK for the rear to come around or initiate the slide with pulling the e-brake. I wished the OEM STi rear LSD had a stronger lock-up.

I run a '04 JDM STi 6spd driveline from flywheel to the Brembos; R180 OEM 2way LSD.
 

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STi swapped SF5, WTF?
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Discussion Starter · #7 ·
I have heard all of the supposed bad things about the OBX diffs in other cars where the washers need to be replaced but I am still waiting to see one fail on a Subaru where the washers replacement would have helped.

And FujiK, I hear what you're saying about the KAAZ but that diff is a lot of money and I don't think I would ever get my money's worth out of it with my driving. The JDM MLSD is a lot cheaper but the question is whether or not it is worth the $3-400 if my car already has the VLSD.
 

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MY99 GF4 EJ227 JDM 6spd
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And FujiK, I hear what you're saying about the KAAZ but that diff is a lot of money and I don't think I would ever get my money's worth out of it with my driving. The JDM MLSD is a lot cheaper but the question is whether or not it is worth the $3-400 if my car already has the VLSD.
oh it makes a BIG difference!!! A MLSD (clutch-type) will out perform a VLSD anyday in terms of performance! I wouldn't get a VLSD ever again. The STOCK JDM LSD are fine for what they are. You could get used to them. Later you'd want a stronger one so you can really have fun. hehee

You gotta spend the $$$ if you want to have real fun! Save a little more and you'll have it! I've put paycheck after paycheck into my little wagon. It is worth it if you are really going to have fun with the car.
 

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01 STM RS EJ257, 6MT, Brembos
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edit: i guess is missed your question, lol. from what ive read, the viscous rear lsd is better than the mechanical, sti's come with rear viscous lsd and mechanical front since v5. there is detailed info on here about it, but you kinda have to dig. i cant recall any specific links, sorry.
Viscous is not better than mech, just more reliable and easier to drive on the street because it "grabs" less than mech.
Older JDM STI's had mech LSD's, USDM 04 STI had Suretrac mech LSD. Everything is viscous now and viscous sucks because it doesn't grab right away and as the fluid in the diff ages so does the diffs ability to lock up. Over time your viscous LSD can actually start to function more like an open diff.
If you want the best LSD you can get (aside from purchasing a new Quaife, etc), go with an older JDM STI mech LSD.
 

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'99 Hybrid RS Coupe
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I've got a V2 or V3 JDM WRX 4.11 mechanical rear LSD in my RS. It's great, but I can't wait until it snows to try it out in that.
 

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STi swapped SF5, WTF?
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Discussion Starter · #12 ·
I've got a V2 or V3 JDM WRX 4.11 mechanical rear LSD in my RS. It's great, but I can't wait until it snows to try it out in that.
I read you thread looking for some clues but you went from a Non LSD to a MLSD so you would have definitely seen improvement no matter what.
 

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overdeveloped beater
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Don't bother with a Quaife rear LSD unless you're doing gravel events. The rear wheel lift on the Impreza just makes the LSD act like an open anyway. The front Quaife is a different story....it's awesome, just like the OBX clone.
 

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STi swapped SF5, WTF?
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Discussion Starter · #14 ·
Don't bother with a Quaife rear LSD unless you're doing gravel events. The rear wheel lift on the Impreza just makes the LSD act like an open anyway. The front Quaife is a different story....it's awesome, just like the OBX clone.
I have seen a few of your posts regarding LSDs on Nasioc. So you think that after doing the front OBX the rear viscous is more than enough for an N/A car?
 

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overdeveloped beater
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Not really. I mean, it depends on the usage. For most things, the viscous diff is okay, but if you're really throwing the car around, you'll want more from the rear end than it can provide.
 

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STi swapped SF5, WTF?
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Discussion Starter · #16 ·
Well, I don't really do much more than backroad trips right now so maybe I will just keep it with the VLSD????????????????????
Storm, I know you have a car with a Quaife and another with the OBX fronts, what are you using for rear diffs(I know you auto-x but just out of curiosity).
 

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overdeveloped beater
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OEM Subaru clutch type LSD's. Both came from a 1989 XT turbo. Axles came from a 91-94 Legacy. The EJ25 will overpower it if the wheel stays airborne too long, but the level of torque transfer is enough to vastly increase our corner speeds. In the winter, the car just pulls through junk like a real 4x4 should.
 

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STi swapped SF5, WTF?
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Discussion Starter · #18 ·
OEM Subaru clutch type LSD's. Both came from a 1989 XT turbo. Axles came from a 91-94 Legacy. The EJ25 will overpower it if the wheel stays airborne too long, but the level of torque transfer is enough to vastly increase our corner speeds. In the winter, the car just pulls through junk like a real 4x4 should.
Is that rear diff much different than an early JDM WRX?
 

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overdeveloped beater
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It uses the same guts. PN's are the same. If there are any differences, it would be in the axle engagement. Mine have hollow stubshafts bolted into the center section of the diff, and the axles are female at the diff end. They secure with spring pins just like the fronts. I just posted a ton of pics in another LSD thread.
Is that rear diff much different than an early JDM WRX?
 

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01 STM RS EJ257, 6MT, Brembos
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^^^ Now thats very interesting! Old XT turbo diffs are pretty badass, who woulda thought.
 
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