GPS? Are you being serious Old Bear? I didnt even know this was a thing. I haven’t taken the tail shaft housing off yet , I just know it doesn’t have cable and gear outlet, it’s got an electronic connection, I assumed it would have a reluctor or something other than a gear, maybe I should look!
I have never seen an aftermarket electronic speedo that was you were not able to calibrate to whatever setup you have or they operate off a GPS
sensor with no calibration needed.
Some (Dakota Digital) you drive 1 known mile and others require you drive 2 known miles.
If you are trying to run your original speedo I'm not sure if you can do that.
I’m going to be running the original speedo to the car, Not electronic, I need to remove the electronic stuff, whatever it may be, and use a driven/drive gear with cable. I’ll take the housing off later today and see what’s in there.
depending on which trans / tail housing you have now ,,
it could be the large or small VSS sensor hole.. maybe ??
you may need a different tail housing to convert to a cable drive.. 700R4 parts
I have a Cable-X Box on my 4L60E, seemed to work good,,
it converts trans elec VSS signal to a cable drive motor..
there not cheap ether, 300$+ Cable-X Speed-Box VSS to Cable speedo Search
This is what I have, and I need to adapt it to a cable for a 72 El Camino speedometer. It’s a steel gear, or a reluctor, nothing like the plastic ones, I’m not even sure how it’s in there, or how I would get it off, there is not hardware, probably have to use a puller.