If this is the case, I am not too concerned. JD wants customer satisfaction and with all the tractor companies competing with each other, they will either build the engines themselves or find a good reputable company. I also am not worried with having a JD with a Yanmar engine. Great engines with a company geared on customer service.
I hear ya...I've owned 3 JD tractors -670,4210 and currently 3320. Never once did I have a problem with the Yanmar engines in these tractors. At least not yet anyway....