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SpeedO not working.

Robert Rabe

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Me and my dad built a 94 chevy short wide. Put a crate 383 carb motor and a HPbuilt 700r4 trans. Using gauge and wiring that came in truck. Using speed censor out 94 and changed ring in tail shaft for it.. I cant get speedo to work what do I check or do i need something more...
 
Hello RR, welcome to the forum.
Are You sure that this is a 700R4 transmission ? In 93 most all the transmissions went to the 4L60E which is a 700R4 but instead of a cable to determine shift pressures it used electronics. if it is a 700R4 then it will need the throttle body from the previous years to 93 and also tha cable and bracket to control the transmission. Without the cable, it will destroy the transmission n a very short distance.
 
Did you keep the VSSB hooked up? There should be a 40 tooth reluctor that passes past a magnetic pickup speed sensor, it sends a low AC voltage pulse to the vssb(vehicle speed sensor buffer) module in turn converts the AC signal from the speed sensor into a 4K ppm 5 volt square wave DC signal for the ECM and cluster as well as a 40 pulse per shaft revolution square wave DC signal for the ECM to shift the trans, and a 128k ppm signal for the abs. The 94 speedo does not work directly off of any speed sensor, but instead a square wave 5 volt dc signal of 4k ppm.
 
That's the white square piece behind glove box?? I'm checking that next. Should the be voltage on any wire at speed senser??
 
The speed sensor produces a low AC voltage when the reluctor passes passed the sensor, that signal goes to the vssb.
 
Ok so no voltage on any where when still ...vssb is probably issue..but from there it goes to instrument panel right..
 
My wires r way different and 8 wire s
7 one plug 1 wire in other..I'm not running motor with ECM or the Trans..
Is ther any way to wire around and get speedo working. ??
 
The vssb is a stand alone box. You either use a vssb or buy a dakota digital box to run your speedo. There is no way to directly run the speedo off of a speed sensor as the speedo only works off of a 5 volt square wace DC signal of 4k pulses per mile. The vssb is a pretty easy setup to use, power, ground, the 2 speed sensor wires, and a output wire to the speedo.
 
Ok I need to check wires better..I guess..need to get a power probe ..or run new wires from speed sensor to VSSB then back of instrument panel..
 
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