Here is alittle tidbit that might help you start your research.
There was a John Udell living in Artemesia Township, Grey County, Ontario in the 1860's. He resided on Lot 32, Concession 5, North of the Durham Road, in Artemesia Township. This would have been near the village of Portlaw which was situated southeast of Flesherton, Ontario.
According to the history book, 'Split Rail Country', John Udell had obtained the above section of land from the Crown. In 1864, it states that he sold the land to Charles Stafford. No further references are made to his name.
I might add that his name does not appear in the 1871 Ontario Census for Grey County. From the information that you had stated, he might have migrated to the States in 1864, after selling his farm in Artemsia Township.
Hopefully, this information will provide you with a starting point to retrieve further details.