A friend has a 51 Ford V8 non OD and today about a block from home he said it broke. I went by there thinking it was probably linkage related and what I found is that it will shift into all gears normally and shifts feel right but while in first or reverse it will clunk loudly and jump out of gear, if you put it back into gear it will move about 1 foot and do it again. It seems like perhaps its one revolution of the gear inside and it knocks it out of gear again. 2nd and 3rd gear works normally. I suspect maybe a broken tooth on the cluster? Any ideas Thanks.