H1B transfer from one employer to another with Approved I-140

[Teja1029]

Hi Friends,

I have completed my 6 years initial H1B quota on March 2013. My current employer is processing my green card, I-140 is approved in Feb 2013 and received H1B visa extension until March 2016. I would like to move to a new employer (permanent position) and I would like to understand what the process is and how long it will take to transfer my H1 to new employer(permanent position) to avoid any visa related troubles.

Please help me on this?

Thanks
Teja