A few days ago I was CONVINCED that chudder was a word; but looking it up in the dictionary, didn't really find anything that substantiated my idea.
Listening to Car Talk today, the Tappet brothers used the word "judder". A-ha! I thought. THAT'S what I was after.
1. to vibrate violently: an old automobile with a clutch that judders.
Love the sound of that.