Definitions $OD, $E6, $31, & $OE require 2000 pulses per mile input to operate a 4L60E or 4L80E. Both options, DRAC or VSSB, will convert the 40 pulses per driveshaft revolution of the 4L60E or 4L80E into 2000 pulses per mile ( with correct configuration of the DRAC / VSSB jumpers). dave w