I do not know of varying threads for the drive at the dynamo. I think it is the same Lucas angle gear drive on all 22 A dynamos, but I do not know what thread it is. Early tractors had an 11 A dynamo, perhaps you have one of those, and that has a different thread? There are two drive cables, but apart from the length (11 A dynamo was shorter, so the cable needed to be longer) I have not seen any thread information.the displayed tachometer distribution does not break anything. I'm embarrassed, but my next question is: I bought a tachometer cable with 7/8 "UNF and 5/8" UNF threads. unfortunately my thread does not fit the small gear at the end of the dynamo. what other thread can there be?