The mechanic was tightening a bearing on an S83 72"" drill leg, using a 24"" pipe wrench, when EE felt a pop in left shoulder area. EE saw a medic at the end of shift and was given an ice pack and a sling and instructed to follow up with EE's personal physician. EE was instructed by EE's physician to get an MRI to determine the damage. No report on the determination yet.