Using an electronic speedo with TBI and 700R4?

[ChevyTech]

It is a DRAC.

Open it, and take a photo of the jumpers, and I can tell you the divide ratio which will determine if you need to recalibrate it or not. Or maybe you are just going to get a speedo working before you worry about if it reads the correct speed or not.

A 1991 DRAC should only have 7 jumpers.

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This is the wiring for a 1993 DRAC which has an electronic shifted transmission but it may help you with wiring your in.
DRAC wiring

From 1993 C/K Schematic

C15 - Speedometer output - Light Blue with black tracer
C14 – Blank - used on M & G vans
C13 – Trns output speed to ECM/PCM – Brown
C12 - Vehicle speed sensor input – purple with white tracer
C11 - Vehicle speed to ECM/PCM (M30) – (Dark Blue M/L,C/K, G)
C10 - Vehicle speed to RWAL – White
C9 - 12 volt ignition – (Brown C/K) (pink & black M/L,G,S/T)
C8 - Ground – Black with white tracer
C7 - Vehicle speed sensor input – light green with black tracer

Small connector:
Blank
Blank
Blank
Speed signal to Cruise control – Red with white tracer


M30 - TRANSMISSION AUTO 4 SPD, HMD, 4L60-E, ELECTRONIC
C11 is brown & white on S/T trucks