Members of The LCMS "have voluntarily accepted the LCMS Constitution and agreed to abide by its provisions. This means, above all, that we accept 'without reservation' the Synod's confessional base, Holy Scripture and the Lutheran Confessions." (Individual members of congregations, technically speaking, are not members of The LCMS. They are members of an LCMS member congregation. Whether one is an ordained member of synod or holds baptized/communicant membership in a member congregation, many have held that the basic idea of a synod is that we would all be walking together with a common confession of faith.)
One would think that would mean a rather homogenous group. And Dr. Kieschnick, in a recent letter to the WSJ editor, has denied that the LCMS is sharply divided.
There had been a prevalent idea that the synod is merely advisory in nature. This was the trick many use to get away with doing their own thing in matters of doctrine and practice. But now, the tide seems to be turning and members of synod are going to have to tow the Kieschnick line.
At one point in its history, the LCMS attempted to tighten things up a bit with "Resolution Nine" which stated: "Every doctrinal statement of a confessional nature adopted by the Synod as a true exposition of Holy Scripture is to be regarded as public doctrine in Synod," and that "Synod's pastors, teachers and professors are held to teach and act in harmony with such statements." That lasted all of 3 years from 1959 to 1962 at which point it was determined by the CCM to be "unconstitutional."
It's pretty clear nowadays in the LCMS that members (congregational, ordained and commissioned) can pretty much believe and act as they will with impunity. President Kieschnick's Blue Ribbon Task Force report which has been adopted by synod in convention and grants immunity to the synodical and district presidents in all doctrinal matters pretty much cinches it.
You can read more details in the PDF document prepared at the request of the 2001 synodical convention entitled: Congregations and Synod: Background Material on the Advisory Nature of The LCMS.