Oliver Wheelset

[Super]

I can't remember exactly what Olivers gear looks like but like Thara has said Oliver has a black flat drive then I think what you have is a clutched gear. Now if it is and the gear isn't slipping but the clutch is, then a fix could be as easy as opening the clutch, a dab of super glue and closing the clutch could prevent the worn clutch from slipping. There is also the option to rob another trackmaster flat drive axle from a junked train to fix it. Have a picture, it may help.