Seems like a silly problem to have but i'm having trouble removing may old speedometer cable from the drive unit. I'm turning the knurled nut but whatever it is attached to must be turning as well because it is not coming lose. Am i missing something here? I can actually see about a 1/16" or a finely knurled barrel inside the drive unit that is spinning with the speedo nut. No way to get any kind of purchase on this piece though. Thanks.