What is the difference between bottom, Center and top shank couplers. The couplers I have on the passenger car keep hitting the switch tracks. What should I do
It is where the knuckle is in relation to the coupler shank: below, above, centered.
Is it the coupler or the little metal "hose" that hangs from it that is hitting the track?
Your problem is likely not the coupler height but the trip pin height which is too low. You can bend the trip pin up slightly. Check the coupler heights with a kadee coupler gauge.