Anyone know tricks to force slave to same speed as primary?
These are identical motors the slave has wires swapped so running opposite direction correctly but while testing I see it doing probably 3-4 revs for every rev of primary.
Mach3, TB6600, Nema 23 82mm 2.2Nm 300oz-in StepperS

Microstepping set wrong on the slave driver.

The main cause is inconsistent settings, especially Steps per Unit, between the main and slave axes in Mach3.
Ensure that the motor tuning, microstep on the TB6600, and slave axis settings are identical; reverse the motor direction in Mach3 instead of swapping wires.
After synchronizing these parameters, both motors will run at the same speed and in the correct direction.