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Old 10-23-2002, 01:25 PM   #1
key master
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Question Can the rear LSD diff from 03 WRX be used on a 03 RS 2.5?

The subject pretty much says it all. I can't believe the LSD isn't an option for Impreza RS 2.5 buyers... I would have paid extra for it. Well, I'm now wondering if it can be bolted in using the WRX part? I have an automatic by the way.

In other words, what's the best way to get a LSD (limited slip differential) into the rear of my car? I'm more interested in the rain/snow perspective and not really autocross performance.

Thanks,
-Jim
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Last edited by key master; 10-23-2002 at 01:36 PM.
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Old 10-23-2002, 03:08 PM   #2
DDMan
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Nope, not unless you replace the front diff too.

The ratios are different.

4.11 (RS)
3.9 (WRX)

Now a LSD out of a 98-99 MIGHT be possible, but that is a whole different story and body.
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Old 10-23-2002, 03:41 PM   #3
key master
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Gotcha.

Well, on my other car (a Chevy), you can bolt up a different ring to the differential and make it any ratio you want. Is that not the case with Subaru differentials? If it is possible, I would think one could unbolt the RS 4.11 ring from the old diff and bolt it onto the WRX diff with the old WRX 3.9 ring unbolted and discarded.

Possible? The only way I see that not being possible is if they are different sizes...?

Thanks for the response,
-Jim

Last edited by key master; 10-23-2002 at 03:47 PM.
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Old 10-24-2002, 03:44 AM   #4
kaos200
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Quote:
Originally posted by key master
Gotcha.

Well, on my other car (a Chevy), you can bolt up a different ring to the differential and make it any ratio you want. Is that not the case with Subaru differentials? If it is possible, I would think one could unbolt the RS 4.11 ring from the old diff and bolt it onto the WRX diff with the old WRX 3.9 ring unbolted and discarded.

Possible? The only way I see that not being possible is if they are different sizes...?

Thanks for the response,
-Jim
your right, the Ring/pinion CAN be swapped, BUT I dont know if axles are different. As sometimes they were between the 2.5s that had/didnt have LSDs
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Old 10-24-2002, 10:59 AM   #5
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You'll need the driveshafts too. They're different on the LSD and open diff.

-IggDawg
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Old 10-24-2002, 11:47 AM   #6
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Quote:
Now a LSD out of a 98-99 MIGHT be possible, but that is a whole different story and body
Only the MY00-01 RS came with an LSD.

IT should bolt right up.
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Old 10-24-2002, 12:00 PM   #7
IggDawg
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Quote:
Originally posted by Impreza Rider


Only the MY00-01 RS came with an LSD.

IT should bolt right up.
just remember, need the driveshafts too. not just the diff.

-IggDawg
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Old 10-24-2002, 04:09 PM   #8
oem
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Default WRX rear diff

The rear diff of a WRX is actually a 3.5 the transfer gears in the transmission are 1.1 to 1 making it compatable with the front 3.9
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Old 10-24-2002, 06:56 PM   #9
RebelINS
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He also said that he has an auto RS so his ratio is 4.44:1

-Wes
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Old 10-25-2002, 07:46 PM   #10
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He needs a rear LSD out of an older STi v4 or v5. It should bolt right in... though he may need new rear axles due to the spline difference.
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Old 10-25-2002, 09:54 PM   #11
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Also he can use one out of an auto Forester S 01. They have the 4.44 LSD.
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Old 10-29-2002, 12:32 PM   #12
key master
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Thanks for the GREAT information all!!

-Jim
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Old 10-29-2002, 03:36 PM   #13
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Ya, the rear LSD out of a 2000-2001 auto 2.5RS, auto Forester, or manual STi v4 or v5 will ALL work.
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