How long do you have to be in a unit before you can request to switch?

First of all you are in a low density MOS, not many of you, switching units for the sake of switching does not happen. If there are other circumstances the CSM usually reviews the situation and makes a recommendation to the CO. This is of course only if the unit is on the same installation, otherwise you are talking about a full PCS move, there would have to be extreme personal circumstance that warrants such a move. Generally you stay where you are. See your 1SG, he will know more about the current unit policies than anyone on RP

How long have you been in the unit? Also, are you Reserve, Guard or Active? For Reserves (and possibly Guard)....if you promote into the unit, you have to stay in that unit for 1 year (when promoting into a SGT or SSG slot). You will want to research AR 140-10. That will have your definitive answer.

SPC (Join to see) you can request a transfer anytime you want. The devil is in the details. CSM Darieus ZaGara and MSG (Join to see) provided good context that may cause a Commander to deny the request.

There is no single set of circumstances that would guarantee anyone here to say a request would be approved.

Talk to your chain of command.