What is wrong with the old Gospels that made Jefferson want to compile a new one? He didn’t talk about this in public, but in his private correspondence he was very frank:

The whole history of these books [the Gospels] is so defective and doubtful that it seems vain to attempt minute enquiry into it: and such tricks have been played with their text, and with the texts of other books relating to them, that we have a right, from that cause, to entertain much doubt what parts of them are genuine. In the New Testament there is internal evidence that parts of it have proceeded from an extraordinary man; and that other parts are of the fabric of very inferior minds. It is as easy to separate those parts, as to pick out diamonds from dunghills. (To John Adams, January 24, 1814)

We must reduce our volume to the simple Evangelists; select, even from them, the very words only of Jesus, paring off the amphibologisms into which they have been led by forgetting often, or not understanding, what had fallen from him, by giving their own misconceptions as his dicta, and expressing unintelligibly for others what they had not understood themselves. There will be found remaining the most sublime and benevolent code of morals which has ever been offered to man. (To John Adams, October 12, 1813)