Thanks for your help Mark. Yes I will try a lock washer under the nut but the shaft turns in the motor when it starts getting tight,makes it difficult to get really tight but it also makes "positioning" or placement of the bracket not crucial because it spins around still. In other words you can position it as needed to connect the ball back in its joint on the wiper rod when reinstalling I think.The wipers are hand-clap style so the shaft turns only in one direction. Hope this makes sense =). Thanks
Nash