[trumpthero786]

I'm assuming you are directly driving the BAG motor with no gearbox. We've successfully used FTC axles, collars, wheels, etc. on the output shaft of a plain old BAG motor, but I'm also assuming that you want to attach a sprocket to drive the chain. In that case the best thing you could do is put a 1:1 VersaPlanetary box on the motor. It will not change the motor, except in length and it will give you a 1/2 hex shaft (or 3/8, if that's what you want to use) to put on whatever part you need to. You can then put on the sprocket or belt pulley that you want on it.