I have 2 GS4 4-8-4 War baby's and have the same problem, The drive wheels come apart  My first one looks like it was fixed before, and a poor job at that. but it has come apart and I had to purchase  the cylinder assemblies to repair it, and it again came apart is there some way to fix these issues? I love the look and style of these big engines. Any help would be much appreciated.... I also read a post from 2008 about a guy that had similar problems with the the plastic half mooned axles, but unfortunately, didn't see what his resolution was