GMECM Digest V1 #162

[Shannen Durphey]

Peter D. Hipson wrote:
> 
> Gee, got me... <g> virtually all vehicles with electronics: a TCM/ECM needs
> to know how fast you're going. Ditto for the electronically controlled
> transmissions, too.
Early vehicles with speedometer cable driven VSS units used a speed
sensor buffer, not a DRAC.  Speedo cables are calibrated to 1k rpm @
60mph.  Early speed sensors had 2 pulse per revolution output, hence
the 2k ppm speed signal.  This signal was cleaned up and sent to ECM,
or doubled and sent to the cruise module.  Also, I haven't heard of
the DRAC used in cars.  I believe DRAC usage was tied highly to Rear
Wheel Anti-Lock brakes in the early days, because of the 128k ppm
speed signal used by the RWAL controller.  I don't know of any cars
with RWAL, so there's no need for the DRAC.  Speed signals are a bit
of a mix-n-match throughout the model years.
Shannen
> 
> At 05:06 PM 6/25/99 -0600, you wrote:
> >Which vehicle(s) used the DRAC as orginal equipment ?
> >
> >----------
> 
> Thanks,
>         Peter Hipson (founder, NEHOG)
>         1995 White NA Hummer Wagon