I'm just getting into trains again and I've been tinkering around with some old Jupiter 4-4-0s just to see how they work and come apart. The worm gear came out and doesn't seem to want to stay in place now. I thought maybe it was broke but I can't see a broken shaft or anything. What am I missing? Before I started to "work on it" the wheels would turn as long as I was turning the drive shaft. They would not turn freely by themselves. Can you replace the worm gears in these older models?

I just purchased a new, never used / old stock Bachmann 4-4-0 Confederate train set. When I first tested it before setting it up, it worked. After I set it up, it ran fine. About 8 hours later, when I turned it on again, the light came on but it would not run. After playing around with it, I found that if I push down on the back of the tender, everything works, forward and reverse. As soon as I take off pressure, the wheels stop turning but the light stays on. Has anyone encountered this problem or have any idea what is wrong? I would appreciate any help.