I have a Kenworth T680, just put a clutch and suitcase kit in. Left the shop and driver came back next day with a rattle/ bearing noise coming from bellhousing area. Would only do it if you let off the clutch quick and would go away with the clutch depressed. Thought it was the input bearing got damaged so pulled it all apart and could not find any damage to bearing, input shaft, pulled top cover of trans, no issues seen. Pulled bellhousing off trans, countershaft bearings look ok. Dropped clutch and flywheel, no issues. Checked crank play and found it has a good bit of play, spec is 0.004"- 0.020". Waiting on my dial indicator to show up tomorrow to see exact amount but it was more than that. Pulled pan and #4 main bearing and thrust bearings, they have some wear but not excessive. Cant see anywhere that the crank is broken, whole thing moves back and forth when prying it. Any ideas what else to check other than dropping rest of main caps out?