My 38 ton shay has a surge mainly slow speed forward on 8' dia. curves, reverse runs much smoother & straight track smooth too. Track Is good Loco is lubed and broken in couple of hours. I heard that the problem might be overly long screws on truck side frames that are touching gears on inside of power trucks. Anyone have any insites on this problem?
Never, ever seen overly long screws in sideframes.
However, for 11 years I've been fighting this.
Single-lead worms and worm-lock.
Unequal motor speeds exacerbate the issue.
Try a downgrade with 20+ cars.
I have opened motors, shimmed armatures, different lubes, nothing fixes it.