Hello to everyone i signed up yesterday so im new to any car forum's. Always loved subaru's espically that noise from the boxer engine cant beat it. Anyway i posted a new topic as i required info from members regarding a rear diff that i need to replace asap, iv had no replies why i dont know isnt car forum's ment for these things???

Welcome along. I'm pretty sure someone will pop in and answer the question. We don't all sit monitoring the forum 24/7 :D it can take a while to get a response.

Hi, and welcome.

Chances are, people haven't replied about the diff because they don't normally go wrong, so folk normally don't touch them

Welcome to the club
 
Regarding rear diff a quick search on google came up with this

'There are many rear diff options, and any of them can be used as long as the final drive matches the final drive of the rear diff of the donor car the transmission came from. Front axles should be interchangeable, but newer axles are thicker. CV strength has remained the same and are not a weak point. Rear open diffs can be found on most Subaru models. Rear LSD s came on some Legacy Turbos, Some SVXs, 2000-2001 2.5RSs, and 2002+ WRXs. While final drive ratios vary, the axle splines do not. Your diff choice governs which rear axles are to be used. You will either need rear axles from an open diff Legacy or GC/GF/GM Impreza for an open diff or rear LSD axles from a 2000-2001 Impreza 2.5RS (ask for axles from 05/2000+ to be safe) for a rear LSD.'

At the bottom of the post here: http://www.subaru-impreza.org/forum/modifications-tips-tricks/29706-info-subaru-engines-conversion-principles.html

And a tiny bit of info here: http://www.rs25.com/forums/f4/t40400-noob-rear-diff-question.html

 

So seems like most are interchangeable, just check for ratios of final drive