VSS and aftermarket speedo
 

Hi, this is my first post so I apologize if I make any mistake. I've searched both this forum and the drivetrain forum and didn't find the answer to my question. :search:

My question is really quite simple. I have a 1st gen chevy 350 crate motor mated to a T5 from a 92 5.0 camaro. Since the motor doesn't have a computer I don't have to worry about feeding it the VSS signal and all that.

I'm a little confused on the VSS wiring itself. On the sensor there are 2 wires, yellow and purple I believe. My aftermarket speedo is asking for 1 wire. I read that the VSS wires are sent to a buffer that converts the signal to a 4K signal in a green wire and sent to the speedo. I don't have that buffer.

Any guidance on how to hook the VSS up to the aftermarket speedo? Is there a way to hook the VSS straight to a speedo without using a buffer?

I asked the vendor and they only support wiring up to the pinout on the gauge; anything after that I'm on my own.

Thanks.

Re: VSS and aftermarket speedo
 

ATM-5291 < i think thats all you will need but im not too sure. i myself am switching from a mechanical to electrical speedo on a 350 backed by a T5 and cant find to much info on the matter. that part is on summit by the way.

Re: VSS and aftermarket speedo
 

Thanks for the part number. I think right now my only option if I want to reuse the VSS is to find that buffer. Do you know where it's located on the Camaro or any other model? I saw that it's also available in other GM RWD cars as well.

I'm using a RacePak speedo.

I think my only choice is to go with a split collar attached to the driveshaft.

Re: VSS and aftermarket speedo
 

ive got no clue where to find it.. Id assume just trace the wires and grab anything that its connected to haha.. ive only dealt with mechanical speedos

Re: VSS and aftermarket speedo
 

there is the option of getting a SGI-5 box from dakota digital, that will take both your VSS wires and send one out to your speedometer. It is really more for a T-56 swap to re-calibrate the pulses going to the ECM.

I'm not a hundred percent on this, but I believe one of the wires from the VSS is a signal ground (I think the purple one), and I think you could just ground that out and run the yellow one to your speedo.

Re: VSS and aftermarket speedo
 

I saw info for the SGI-5 box as well. I'm speculating that one wire is ground and the other is signal as well, but I have no idea.

I'll try hooking one or the other up and see if I can generate a signal for the speedo.

Re: VSS and aftermarket speedo
 

Kenn, search for sgi-5 or dakota and you'll find ALOT of info. I'm pretty sure you'll find what your looking for there. There's also the search for " dakota autometer"

Re: VSS and aftermarket speedo
 

I searched the SGI-5. I don't need the converter because Racepak has its own built in converter. I just need to figure out how to hook the VSS to the Racepak.

So far the only positive response I've found was to hook the VSS to the buffer, and hook the speedo output of the buffer to the Racepak.

I'll try to hook Purple to ground and Yellow to the Racepak and see if I get any sort of signal. If I get anything it's good to go. The Racepak and do the conversion on its own.

Re: VSS and aftermarket speedo
 

i have heard one is just a ground and the other is vss signal. also heard it doesnt matter how ur hook it up

Re: VSS and aftermarket speedo
 

Yeah, like I said it is really just to convert a signal to the ECM and cruise control. I've heard the same thing that jayk2k3 said, that it doesn't matter they are both sending a signal and both can be grounded, I know that that is true for the T56 VSS but not positive for the T5 VSS, should be though since there both electric signal outputs.

Re: VSS and aftermarket speedo
 

Thanks for both of your inputs. I'll give it a shot and see what happens.

I got a peek at the Mitchell On Demand and it lists Purple as ground and Yellow as sensor signal. I'll report back if I have any problems.

Re: VSS and aftermarket speedo
 

If it is like my Autometer, you ground one wire and connect the other to the speedometer input. (Can't recall which wire you ground.) Then you put the speedo in "calibrate" mode and drive an exact known 2 mile distance. Then you stop and take the speedo out of calibrate... and you're done. The signal must come from the speedo VSS, not a computer.

The tranny is sending out magnetic pulses and the speedo needs to learn how many pulses per mile are being sent.

Here's the Autometer instructions:

"Onto the calibration procedure itself, the easy part. Current Auto Meter Speedometers use the Trip Reset Button as the calibration button, some earlier Auto Meter Speedometers use a separate calibration button. We include a pushbutton that is used for the calibration steps on models which require the separate button. Once you have everything installed and before you start the motor, follow these steps

1. Press and hold the button while starting the vehicle. Once the motor is running, you can then release the button after the pointer goes to the highest MPH reading and stays.

2. Drive to the beginning of your carefully measured 2-mile distance, and stop. Press the button again, and the pointer should then go to half of the maximum MPH reading, and the speedo is then ready to be calibrated.

3. Drive the two miles, stop, and push the button, the pointer will drop to zero and the calibration is complete and the speedo should begin indicating the speed when you start driving. "
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Correction to what I just said: The signal must come from the tranny VSS. :eek:

Re: VSS and aftermarket speedo
 

Thanks for the post. I have no problem with calibration. I'm just no familiar with the VSS on the T5 itself.

Right now Purple = ground, Yellow = VSS pinout on speedo. VSS = sine wave.

Does anybody know how many pulses the VSS generates for each revolution of the output shaft?

If I can figure this ratio out then I can figure out the wheel speed per VSS pulse and it's not a problem for me to calibrate the speedo. If not I can just shadow another car and the speedo with be in integer multiples of what the actual speed is and I can dial it back without problems.

Thanks for the help.

Re: VSS and aftermarket speedo
 

Maybe this will help...

Re: VSS and aftermarket speedo
 

I've read through that doc in my search. It doesn't provide specs but I think I'll be able to pin it down with some field testing now that I have my car back.

Thanks for everybody's help.

Re: VSS and aftermarket speedo
 

Quick update. I grounded the Purple wire and fed the Yellow wire to the Racepak speedo. It's showing a reading but I still have to calibrate it.

When I reversed the wires it didn't show anything. I pulled up the Mitchell's wiring diagram and it shows Purple = ground, Yellow = sensor signal. I'm not using a buffer or SGI. Just the VSS straight to the Racepak.

Thanks for the help.

Re: VSS and aftermarket speedo
 

Quick follow up question.

Does anybody know how many pulses the VSS generates per driveshaft revolution on a V8 T5 with digital VSS?

I know that my driveshaft turns 3520 revolutions per mile. I'm going to pace a car and set the value to integer multiples of 3520.

If somebody could put me in the ballpark that will help reduce the amount of experimenting and will help me zone in on the correct value. Thanks.

Re: VSS and aftermarket speedo
 

I think it is around 4000 ppm

Re: VSS and aftermarket speedo
 

Kennn, I'm considering the RacePak for my project and I'd like some feedback. How practical is it for every day? A picture of it with your car at idle would be really neat.

I have a VSS buffer from an '86 T/A if you need it.

Re: VSS and aftermarket speedo
 

Thanks for the offer. I don't think the VSS buffer will do me any good at this point. All the calibration can be done via the RacePak. If I get stuck I'll take you up on your offer though.

In all honesty, the Racepak Street Rod dash is good if you don't want a thousand of different gauges. Most of the stuff on it works pretty well.

My main complaint is that some of the software isn't completely accurate according to the manual. There are a few small bugs. Not anything major but enough to annoy you.

It is a little clunky to use and set up. The buttons take a lot of effort to use, and it can't display more than 5 channels at the same time unless you buy the optional software and program it yourself.

If you just need something that works I guess it's cheaper than buying individual gauges.

There are things I do like about it, like built-in fan controller, adjustable warning lights, compact size, ability to display everything you need on a street rod.