H1b transfer while on Cap-Gap Extension

Hi,

My Current status is OPT, but it will expire in July 2014. My h1b petition is approved in 2014 and I have also received my i797 and I have also informed the DSO and they have sent me the new Cap-Gap i20 as well.

Now my question is, can I change the employer before 1st Oct 2014, if the new employer is willing to transfer my h1b?

I am aware that I do not need to inform them when I ask the new employer to transfer. But can the old employer create any problem for transfer or withdraw my approved h1b by any chance?

Thanks in advance!