Just one pinion drives the axis (the "master") although the second pinion is "preloaded" to remove the backlash (the "slave"). The preload is developed electronically having a Specific motor controller; these programs can also be put in place to drive jointly through cycle situations when backlash will not be important. https://gearbox-cvt64296.verybigblog.com/32006599/how-much-you-need-to-expect-you-ll-pay-for-a-good-gearbox-cvt