Combines Engine vibration on 72

I'd check behind PTO flex coupling to see it hasn't built up uneven with dirt. Clutch pulley on mainshaft can also do this. I think vibration dampners can be checked somewhere but I've always just replaced. Bad viscous dampners on the old Allis would cause air conditioner belts to fly off all the time. Haven't replaced any Cummins dampners. Might be getting time for a tune up.

When you say behind the pto flex coupling, do you mean take it off and check behind it or can I check elsewhere on it. I did have it tuned up about 500hrs ago but maybe it needs it again. I think the book says every 1500 hrs.

we have lost a couple of pto shafts, later productions beefed up the output shafts. Started with vibration.

Yes I believe you would have to pull PTO and coupling to blow it out. Not to hard to do to check it out. Good luck