I bought this set brand new in November for my son for Christmas. He was delighted until the train stalled and motor whirred.
We tried adding weights, cleaning the tires and rails, but the slip would come back. After he went to bed, I took it apart and found the worm gear slips on the axle in the truck after minimal resistance is applied to a drive wheel.
I thought these gears were pressed onto the axles, and even perhaps splined. This was an expensive set that's basically dead on arrival.
I will talk to the hobby shop where I purchased it. I've read some other posts where people talk about cleaning the parts and perhaps using CA or Loctite adhesive. I haven't decided whether to try and correct it myself or have the hobby shop make it right.
What gives with the quality Lionel? If you want to attract children to the hobby you can't make them cry on Christmas.
The lesson for me, though, is: Open the box and test it first. :-O