I just bought a rear wiper motor as it is missing on my TD5 It came in our favourite blue marked box. Oh joy. Needless to say it came without the nut that goes over the shaft to secure it to the door. Can anyone tell me the correct nut size for this? Using some pretty rough means of measurement it looks like it is a 5/8-18UNF but I want to make sure before I spend to much time chasing imperial nuts in this land where metric is king.