Abstract: An anti-backlash tractor assembly for the accurate registration of bi-directionally transported endless paper to the printing mechanism of a printer. When mounted upon the printer in an operative position, a resilient biasing device will urge the printer driving gear and the tractor assembly driven gear together for dynamically eliminating backlash therebetween and for dynamically compensating for gear eccentricities and other drive train variations. Also, in the operative position, a manual adjustment lever is provided for establishing nominal paper tension.