We have discussed this topic over and over again this past year or so. What happens when you move from an established domain to a new domain name? What can you expect to see in terms of traffic drops from your Google referrals, specifically? That is the topic of discussion in this WebmasterWorld thread.
I would simply like to highlight two select member's experiences with making this type of move.
First from WebmasterWorld admin tedster:
I would strongly consider having a GWT account that ties the old domain to the new one. You don't need to submit an xml sitemap unless you like that idea, but the crawling data alone could be valuable -- an giving Google a solid reason to trust the new domain could only help. We moved a domain 20 months ago from the .org to the .com of the same "rightmost non-generic token" (in Hilltop language.) The old owners had allowed the domain to fully expire -- there was a clear break in the Whois history and the new ownership was clearly the same as the .org ownership. We did a domain wide and url-specific 301 redirect and the new domain's url structure exactly mirrored the old.
And still there was a major dip in traffic and an 8 month quarantine from the trust filters. Reports I've heard this year are that the process can be much faster, but I would still pull out all the stops and give every possible trust signal. Where possible get inbound links changed -- especially deep inbound links. Get new IBLs, both to the domai root and to deeper pages. A Press Release might help a lot.
For an earlier domain move, back at the begining of the so-clled sandbox effect, we did not use 301's, we placed dumb old "we have moved" links on every page. To my memory, that changeover actually went faster (5 months), although I'm not recommending it. I just wanted to mention it as a cautionary tale about the magnitude of what you pla on accomplishing.
Extremely helpful! Here is what member BigDave had to say:
You *will* get a drop in traffic. The absolute best case is that Google takes your current results out of the index and the new pages go into the index at the same time. Google credits your 301s within a month, and takes another month to recalculate everything else.
Since the new domain is not the old domain, it will not get any benefit of any age related factors. You also have a new domain that is suddenly appearing with 50K pages.
If you are lucky, Google will recognize that it simply a new domain name on an old domain. It isn't the sort of luck that I would want to bet a business on.
Sometimes you have to make the move, if you do, use the tools available to you to make the move as "legit" looking as possible. Document every step you make, track the results, be patient and hope for the best. Oh, and don't forget to share your experiences with the community.
Forum discussion at WebmasterWorld.