Surging 38 ton shay

[tommygunner]

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?

[Curmudgeon]

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.