Dissertations tend to be more stringent re resubmission criteria, i.e. you'd usually need serious mitigation for it to even be considered. I have only ever seen a retake allowed once (because of seriously heavy MitCircs), every other time in my departments it has resulted in an Ordinary Degree, and an Ordinary Degree isn't worth the paper it is printed on.
Why don't you want to submit it? Do you have any serious mitigation? You really need to speak to somebody at your institution for tailored advice, and quickly.