I own 51 percent of an LLC and I want to split from the partnership

Do you want to simply withdraw from the LLC and have the LLC continue to do business?  If so, you can transfer your membership interests to the other members.  If done correctly, there is no reason a new EIN would have to be issued, but you should make sure you do not remain as the responsible party for tax purposes.  If you applied for the EIN, and are the majority member, you may be the responsible party as far as the IRS is concerned.  You should pull together your operating agreement and any other relevant corporate documents and consult with an experienced business attorney to make sure the transfer and all other matters are completed properly to ensure you do not have residual liability even after you leave the company.   ***NOTE:  This response should not be deemed as legal advice as facts not presented in the question could change the answer.  Further, there is no attorney-client relationship created by this response.  To obtain dependable legal advice, you must consult with an attorney and present all relevant facts.***