BigRed922

On my 2500hd my oil gauge would normally be at about 60, sometimes more if i was accelerating. Idling, it would be just under 60. Now its hanging around 35-45. Typically at 40. Just checked and its got oil. I did notice a small amount on the oil plug. And i just replaced thr starter. Is it possible i didnt put the starter close enough to the flywheel and the small gap is causing the issue?? Do i have a vaccumm leak?? Need help guys