well most new gear sets come with shims just to be safe i would get some new ones they are pretty cheap make shure you put a new crush sleeve in their as well if you bought them new that shold have been in the set with gears as well just my 2 cents didnt really answer your question just get new shims better safe then sorry
NO DONT LOOSEN IT!!! just leave it your old gears do that from so many roatations just torque it down down right and youll be ok trust me dont loosen it