Thanks for the reply Doneldon.
I don't believe the pilot truck (if I'm understanding the terminology right that is the pilot trucks - the lone set of 2 wheels by themselves?) are being obstructed by anything. They are tracking along just fine, in either direction. It's the first set of driver wheels that cog up (of the 4 driving wheel set). I have looked before to see if I saw anything that would be obviously an intrusion, but could not see anything. I'll take another closer look. I know all the driving rods are aligned properly and nothing on either side of the loco looks out of alignment there. And for info, when the wheels cog up, or get stuck, I have worked them back free and into place, only to have it happen again. So it is a repeating problem.
I don't believe the pilot truck (if I'm understanding the terminology right that is the pilot trucks - the lone set of 2 wheels by themselves?) are being obstructed by anything. They are tracking along just fine, in either direction. It's the first set of driver wheels that cog up (of the 4 driving wheel set). I have looked before to see if I saw anything that would be obviously an intrusion, but could not see anything. I'll take another closer look. I know all the driving rods are aligned properly and nothing on either side of the loco looks out of alignment there. And for info, when the wheels cog up, or get stuck, I have worked them back free and into place, only to have it happen again. So it is a repeating problem.