I have a large scale 4-6-0.  The gear on the drive axle (last axle) turns freely.  When the power is on, the motor runs and all the gears in the gear train turn; however, the power axle and drivers do not move.  When the power it turned off, the engine rolls freely with all six drivers, siderods, pistons etc. working perfectly. 

My question, how does a person go about fixing this problem?  Can this repair be performed at home successfully with limited tools, equipment, etc.?  or is this the type of problem better resolved by sending the locomotive back to the factory where it can be repair correctly the first time?

If it can be done easily at home, what parts need to be ordered?  how does one extract the rear driver  from the siderods and from the frame?  how is the existing gear reattached securely, etc.?

If locomotive needs to be returned tot he factory, should the tender accompany the locomotive, etc?