One  problem car is an Atlas. Your note has caused me to look at the car more closely and I found one set of trucks has larger  diameter wheels than the other.When I couple the larger set to the previous car ,the problem is solved. I bought the car used . Lesson learned.
I did not know there were two wheel sizes.
The second car may have the same problem. It is the old style hook coupler . I don't know the car mfg. I bought this car used because i needed that style coupling to hook up with a new engine returned to me by Bachmann ,
I will study the other suggestionsyou made for troubleshooting & follow up woith you if I gfind anything.
Thak you for your help . I really appreciate it.after I sent in an engine to be repaired. I thought I would change one coupling on this car to the knuckle type so I could pull my other cars which were Bachmanns.

Two of my cars uncouple ever time it passes over a switch or slight bump.. I have noticed their couplings are lower than the mating couplings on the other cars.Is this fixable ?If so how.? Being new top the hobby, I thought the coupling heights would be standard.

I need to change the coupler on my box car. It requires a very small Phillips Head cross head type screw driver. I cannot find such a driver. Can anyone tell me where i can get one.

I suspect you may be right. However, I am a real green horn at this, how do I do that? Thanks

The pilot truck runs up over the point rail

My  4-8-4 "Hudson" derails virtually ever time when going thru my ez track turn out when trying to divert onto the inside track. The train tries to keep going straight. There is no problem when the turnout is in the straight ahead mode. The train is coming off an incline shortly before  the turn out. Any help will be appreciated.