Wilson. I do not know if this will work. I saw it on another website and copied it for reference. I wish I could give proper credit, but I can't find the original again. Perhaps it will help.
"She had a definate hitch in her get-along. At slow speeds she would hesitate badly whenever the side rods reached the same spot in their rotation. I've experienced this problem with a number of 10 wheelers in the past and have a quick cure that has once again worked and she runs as slow and smooth as I would expect.
If your loco does the same, simply remove the side rods and use a reamer to slightly enlarge the holes in the rods. The little extra slack allows things to move without a hitch and compensates for wheels that are apparently slightly out of quartering."
Author unknown!!
"She had a definate hitch in her get-along. At slow speeds she would hesitate badly whenever the side rods reached the same spot in their rotation. I've experienced this problem with a number of 10 wheelers in the past and have a quick cure that has once again worked and she runs as slow and smooth as I would expect.
If your loco does the same, simply remove the side rods and use a reamer to slightly enlarge the holes in the rods. The little extra slack allows things to move without a hitch and compensates for wheels that are apparently slightly out of quartering."
Author unknown!!