Hello ! (I hope this is right category for my thread)

Can somebody give me an advice on following situation?

We have SEO optimized and well-ranked site. We want to separate one part of this site as new one.
It will have its own domain name, structure and pages.

Do you know any ways how to transfer rankings and PR? (I mean how to save positions and PR for the same content pages after separating domain)
Or we should start SEO again from the beginning?

Any answers and ideas will be greatly appreciated...

Thank you.

That's a dangerous move. To 301 a page to an other page of the same site is usually not a problem, it goes smooth usually. To redirect 301 a portion of a site to an other URL is not really the same. It might inherit the backlinks to those moved pages, but the main site cannot crosslink too much with the new site, like it was possible when the pages were part of the main site. It could also be affected by the sandbox if the new domain is fresh.

I would say the serps and all will be affected big time by this. But this is only my opinion.