Formula to find divide ratio when using General Motors  DRAC speed sensor and changing gear
ratios, tire sizes, and etc.


Input Ratio=63360/RC*XR*P/128000


63360= #of inches in a mile
RC= tire circumference in inches
XR= axle ratio
P= # of speed sensor output pulses per output shaft revolution.  The 700R4 with VSS 
(not speedo cable) is 40 pulse/rev.

128,000 pulses per mile is DRAC output to RWAL module in fullsize pickup application.

Rolling circumference is preferred method of obtaining tire circumference.  Mark line on tire
and corresponding line on floor.  Roll vehicle back until tire makes complete revolution.  Mark
2nd line on floor and measure distance between 2 lines.  This is actual rolling tire
circumference.

(Circumference=(Pi)(Diameter) for estimating purposes.)

Look up input ratio on chart to find proper jumper settings.

Notes: 
DRAC is designed to use AC input signal.
73.8" rolling circunference and 3.73 axle ratio yeild 1.00 divide ratio.
747 ECM recieves 1.11hz/mph signal