Cal,

Do you have a manual for you 4240? There is a small trouble shooting section in the back. It does address the plow not trailing properly.
I grew up in PA and spent a great deal of time growing up on my uncle's farm. Every piece of farm equipment my uncle had was Oliver except for a New Idea sickel mower. Then again New Idea equipment was sold by Oliver dealers.
It wasn't until I moved here to Iowa about two years ago that I found out that PA and CA were big Oliver States. Then I remembered that there were two Oliver dealerships close to my uncle's farm that we frequented. So I guess I was lucky growing up. Oliver was the norm rather the exception in my part of northeast PA. I guess the PA connection was helped since Oliver had an implement plant in York, PA.