This question has come up how do I take the thing apart and what does it look like? I have taken several apart, purchased on ebay, and repaired and it is not rocket science. There are many similarities if you are in the right years. HO seeker (google it) has parts diagrams for lots of them. This S-12 is a lot like the F-7 and F-45, and the life like GP-18 proto 2K that I have worked on. On the video I said the wheel truck sets were available but since looking I can't find them. I did replace them on the GP-18 and got those parts from Walthers. It turns out that at least one of these axels is cracked, It was not visible until I looked closer. Also, the wheels were loose on the gear and the train wanted to derail because the wheels wanted to move in and out a little and not track well. [video=youtube;d32BoqZFLH4]https://www.youtube.com/watch?v=d32BoqZFLH4[/video] This is a brief video and does not show the complete truck dissassembly, which only involves taking another clip off and the two sides separate and all the gears are fully exposed. A drop of oil on each of the bearings may be appropriate.