Anyone have any ideas on how to transfer w/out burning bridges?   May still want to be in good graces in case promotions comes around.

If you have legitimate and valid reasons for wanting to transfer then it shouldn't burn any bridges.  I left our S.W.A.T. team a couple of years ago due to a health problem and because I couldn't devote 100% to the team and 100% to my narcotics section.  It wasn't fair to either side if they needed me and I was doing the other.  I explained my reasons to the team and was asked to reconsider but I left.  No bridges burned and I have been reminded several times since of a standing invitation to return to the S.W.A.T. team whenever I am ready.

If you've got a good reason, I would recommend honesty.  Even if some don't agree with your reason, at least they can respect you for being honest.

Good luck

If you're looking at going back to patrol, one way to consider framing it is to tell them that you came to the specialized unit to gain experience and training to make yourself a better patrol officer, now you'd like to go back and spread the wealth and make the rest of patrol better.  That's what I did during my first trip in investigations - I had no intention of staying more than six months, and when my time was up, I asked out.  I went back to patrol, did almost three years, used the training and education, then came back to invstigations.

Be honest and don't make up excuses