partsandservice
Senior Member
Here I am working on another teir 3 6.8 748H. I need to talk theory. I have a severe mid-range vibration. This is a direct drive machine, so the drive line to transmission was removed and vibration remained. Balancer on front of engine is runnig true. Removed what Deere refers to as a dampner( flexplate of sorts) and found the rubber torn but not seperated. So it was replaced. Still there. Removed the new dampner and found the vibration gone. Reinstall vibration returned. The next conclusion is that the new dampner is ouy of balance. Next new dampner has the same result. The engine doues not have any sort of skip or abnormal engine smoke. Here is my theory, The Crankshaft is broken, adding the dampner amplifies the vibration. The Crankshaft does not have excessive end-play. Theoretically it seems possible that the crank is broken and the engine still runs. Practically is the question. I have never seen this. Soon I will have to test this theory as I am at the point it has to be internal and will have to break it down to see.