I get the whole washer thing. I've done the bread clip mod to a 736 Berkshire too. But based on the original post- it sounds like there are a lot of Lionel diesels made in the last 10 years with at least one set of wheels gauged too wide. Putting washers or e-clips on the axle doesn't bring the wheels back into gauge. I'm surprised these things don't bind or derail on switches.
So fans of the washer mod, you're telling me that having one axle gauged wide and the other gauged correctly doesn't affect the operation? Or am I misunderstanding the problem...?