Hello,
I have two 2006 AWD vibes.
I have heard that the 1st gen and 2nd gen rear differentials are the same except the 2nd gen has electric coupling instead of friction / hydraulic coupling.
If that is true, there is a diff for sale on Facebook marketplace for $400:
https://www.facebook.com/marketplace/it ... =undefined
Otherwise, check car-parts.com for the part you need.
After you replace it, check the rear fluid level at each oil change.