Hi everyone totally stuck here I have an 87 model car and wanting to keep orig spedo is vdo cable driven from gear box now I’ve put a 4l60e gearbox newer and it is electronic not a cable that spins will one of thees stepper motors be able to replace the vdo part so I can retain a complete factory look d sorry I’m lost and don’t wanto go with cable X or dokoda dig any help or info would b awesome thanks heaps have a great afternoon. 6 wires on top at back
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It should be possible, but you will need to gather more detail.
Firstly, what speed does the present speedo expect to be driven at? Being a gearbox drive there will be a simple linear relation between shaft rpm and indicated speed, but you will need to know what that is.
Then you can decide whether a stepper or DC motor would be most suitable. A stepper will give the best speed accuracy, but might not have an adequate maximum speed. A DC motor will have a good speed range but might not have adequate torque at low speeds.
Once you have determined the most likely motor you will need to know what sort of signal the new gearbox provides. It is digital or analog, and what is relationship between the signal and the road speed? And that information might require a reconsideration of what motor to use.
Thanks heaps mate I’ll get to working it all out it’s been a night mate and can’t get it on road untill I get spedo working 80k in and can’t drive the thing hahathanks again mate
This is a complex project and hard to build from scratch, involving mechanical and electrical.
I searched for 4l60e transmission speedometer conversion, there are kits to convert the speedo output to work with an old mechanical gauge.
Suggest you check them out first before trying to build something.
The kits I found were not cheap and was a little confusing with not enough information. Some wanted the transmission sent to modify it themselves. (expensive)
Might also be good to visit a local custom vehicle shop, they should be able to help.
Anyway, all the best, excellent project.
Cheers
Jim
Appreciate all the help thanks alot Jim cable X and decoda digital had them both nothing but dramars unfortunately I’m in 80k and don’t wanto have to do it again haha and still not on road bloody cats hahaha have a great day mate
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But there’s no reason for not tackling it. The suppliers make it sound complex, and charge a suitably high price, but the components are standard and it’s only the motor that might require some careful investigation.
The VSS signal from the transmission (which is likely what OP has) is adequately documented and the connecting plug is readily available on line (although it might be already installed). OP will need to connect into that signal and calculate for the final drive and tire size. Or there might be an option to connect into an existing CAN bus. The controller can be any MCU that can count the VSS pulses and drive the motor. The GPS option is not required and can be left out. A short cable kit is also available, but adapting a generic cable would not be difficult: OP could even use the existing cable, although shortening it to the minimum required would be a big advantage. Finding the right sort of motor and making an adapter to drive the cable seems like the only tricky bit. There is no apparent reason for the high prices, (other than the suppliers understanding of their customer base!) so perhaps the motor is the expensive and difficult part of the setup - that would be the right place to start looking.
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Agree. I would enjoy tackling something like this.
The electronics would be no problem for me, the mechanical a little bit more of a challenge.
But given @Roxanne220973 has spent 80k already a $300 to $600 for part that works correctly is not a large cost. (comparatively speaking)
This looks promising, but I would need to read the docs in detail before I bought it.
ELECTRONIC TO MECHANICAL SPEEDOMETER BOX CLIP ON STYLE, GM
Dakota Digital ECD-200BT Manual
Cheers
Jim
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Love the pics, real nice !!!
Pics always help.
Regards
Jim
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Hi Roxanne,
Beautiful car! I hope to own a V8 of some kind before they go extinct.
Have you considered using a stepper motor designed for gauges? That would do away with the cable system. It’s how any car past 2010 or so does physical gauges:
You could run the speed sensor signal to a microcontroller in the dash, and have it count the time between pulses, hence the speed, and actuate the stepper accordingly. Would be quite the task, but might mean your project costs $50 in parts instead of 500.
What do you think, could this work for you? Or should I go into how I think a cable solution could work?
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Reviving this thread because I’ve made the speedobox. You feed it a VR speed signal and it drives a Nema17 stepper motor.
You can adjust it with a couple of potentiometers. No microcontrollers, just plain oldschool electronics.
The set below is made for a Volvo 240 speedometer, but with some dimensions I can print a custom adapter.
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That’s awesome! Thanks for the update this is a great solution. It looks super clean to with the 3d printed parts.
Glad to hear you figured something like this out!
Sam
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Hi All
The original post wanted to convert more modern speedo electrical pulses into mechanical rotation to drive an old speedo. Is that what this one does?? Or does it mechanical drive the stepper which is used to generate pulses, ie; the other way around.
From what I remember of my mechanical days the speedo cable does not rotate particularly fast. I think it rotated a sort of “drum” inside with a magnet fitted to the inside rim. There is a pic up device coupled to the pointer restrained by a light spring and the magnet “pulls” this device around against the spring tension, the faster the rotation the further the pick up rotates.
Sort of like a magnetic clutch is the easiest way to explain it.
Cheers Bob
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It’s exactly what the TS wanted to accomplish.
Original speedo is cable driven from the gearbox. The newer gearbox doesn’t have that, so the rear diff speed sensor or a driveshaft speed sensor kit could provide the correct signal.
To set the speed one has to know the original frequency to speed ratio. For my Volvo 240 that was 150Hz = 100 km/h. If it is unknown, the range can still be found with the pots.
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