Hi I'm building a 3100 , putting a t 5 trans. Out of a 91 s10 the trans has a vehicle speed sensor on it has any one worked on trying to take the output of one of these and used its output to drive a non traditional speedo . I'm thinking since my old speedo doesn't work I'd like to try and gut the gears and place a small motor behind the needle to indicate the vehicle speed in the cab . To get started I need to know what type of signal this is coming out of the vehicle speed sensor . Since it's not in the 91 s10 any more I cant simply go for a ride with a volt meter hooked up to it I suspect it will be an ac voltage but need to know the approximate voltage to expect at about 55 mph . Can't seem to find any documentation ?
Output of vehicle speed sensors do not vary voltage directly with speed. What they do is send a fixed voltage pulse up the wire X number of times per revolution of the output shaft of the transmission. The faster you go, the more pulses per second.
I just remove the sensor from the trans and there are no moving parts and I can see a cog on the output shaft . Probably there are pulses like you had said and the frequency of pulses goes up as speed increases . A frequency counter of some sort would be needed to figure vehicle speed . What is the common solution out here for this issue ? Do people seek out older transmissions to not have to get rid of there speedometer cable or is there any aftermarket product that can read the pulses available and drive a aftermarket speedometer .
VSS needs an electric speedo, or... A box to convert the pulsed output signal to a rotation. Such as this: http://www.abbott-tach.com/cablex.htm Good luck!
We have used both the converter and the gps speedometer. Converter works well but gps has several advantages and one disadvantage. It is dead accurate no matter what gears you use and tire size change has no effect. It hasn't happened to me yet but there are some dead spots with no reception in remote areas. You can get a gps with all the whistles and bells that shows all the stuff a regular Garmin shows but I figure having that distraction would be as bad as texting.
I used Classic Instruments gauges on my truck and the speedo has a pulse generator used with it. I don't know if the T5 trans pulse gen would be compatible, but I'll bet a phone call to Classic Instruments will yield an answer?
My electronic gauges were manufactured by New Vintage. I have their electronic sending unit instead of a mechanical speedometer cable in my '52 GMC, but the following information about vehicle speed sensors comes from their web site. ELECTRONIC SPEEDOMETER NVU programmable speedometers, like all speedos that are electronic, require a pulsed signal. Typically a square wave or AC sine wave is needed so that the unit can count the pulses. To program, the speedometer counts the number of pulses in a mile and self calibrates. Once set-up the unit counts the pulses per second and points the pointer to the appropriate angle and the odometer is alerted to maintain mileage. Its only math. The signal can come from a variety of sources, the only limitation is the input needs to be between 4000-150,000 per mile and have a strength of 5V. Voltage is the strength, the wave is the frequency.
