Hi RichardVB,
I have found the 3662 Milk car to be a really good operator, much smoother than the older models. I usually test them with the body off, that way you can see where the problems exist. Please check to see that your milk cans do not have the magnets on the bottom, since the 3662 uses the cans without magnets. I have attached the operating instructions.
Keep us posted on your progress.