rear diff

[98outbackpdx]

can the rear diff from a 99 SUS LTD fit in my 98 OBK wagon the SUS now has a 5 speed manual and the outback has the 4EAT auto transmission? my brothers did a 5 speed swap years ago and i found the old rear diff. it would only be as a back up in case something happened to my rear diff which i doubt will happen.
should i keep it or scrap it? it has been sitting on the side of my house since probably 2008 uncovered. the dealer told me i can just put it in with their scrap parts if i don't want it, i would only have it in my car until i could get a new one.

nothing is wrong with my rear diff, it would just be a back up.

[mike-tracy]

The stock SUS diff is 4.44 FD and your outback is the same. I don't remember which year they changed to the phase II rear diff, but I do know, from having a 99 SUS, that its tranny is a phase II. What does that mean? If the SUS rear diff is a phase II, you'll need to swap the input flange with your 98's. Might need to swap the studs as well, if they are a different length. No big deal either way.

If it's chock full of rust it might be seized up. I had one outdoors for a couple of years that was rusty, but not seized. I filled full of oil and am still running it.