Oh no, DON"T use WD40. It is not a good lubricant, more of a rust solvent and penetrant. Trot down to your local hobby shop that deals in model RR and get a tube of Label grease, plastic compatible. Or, do what I do, and use ordinary automotive wheel bearing grease, not the kind with fibres in it, just the old fashioned kind. Also, use either Label oil or ordinary 10W40 to oil the bushings and shafts.