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Retrofitting late model donor speedometers

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Old 11-07-2007, 10:20 PM
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Default Retrofitting late model donor speedometers

OK, I know enough to be dangerous.

I talked to Autometer at SEMA, and they stated that their speedometers require the tranmission speed sensor output. No problem.

But, like many, I would like to keep the stock appearance of the original speedo face. No problem. Gut and paste in an Autometer/aftermarket gauge with the same sweep angle and speed range, then tap into the transmission output. But a new one is $250, used who knows.

What about using a speedo movement from a late model car? For example, an '02 Impala has a very similar sweep angle speed range that I need plus a digital odometer. These can be had for $25 on Evil Bay. How would one determine if the speedometer uses the same 4kppm input that the LS1 PCM outputs? Calibration might be a PCM tuning deal.

Thoughts?
Old 11-07-2007, 10:23 PM
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Old 11-08-2007, 01:34 AM
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???? What are you trying to install this into?

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Old 11-08-2007, 01:55 AM
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1968 Camaro Tick-Tock-Tach.
Old 11-08-2007, 04:39 AM
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As far as I know all of GM's cars (Last 10 years that is) should have a standard protocol for the gauges so the Impala speedo should work with your PCM.


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Old 11-09-2007, 09:54 AM
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Yep, all of the GM electronic speedos use the same signal (4000ppm square wave DC). I looked into doing this and the difficult part was finding one with an odometer in the speedo sweep and not somewhere else in the gauge cluster, but it looks like you may have already found one that would work. Also keep an eye out for aftermarket speedos on evilbay, I picked up an autometer factory second for $50, the lens was scratched but that didn`t really matter since I was prying it off anyway.
Old 11-09-2007, 12:45 PM
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Ive been trying to figure out what pins are what.. i am swapping an LS1/A4 in a 79 malibu, and woul like nothing more than ta adapt the C5 dash i bought to install, tach, spedo, gauges and all (perhaps the HUD someday ) i even bought the corvette underdash wiring to have all the connectors.. but i have been utterly unseccessfull in finding the schematics!
Old 11-09-2007, 04:46 PM
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Originally Posted by deuce_454
Ive been trying to figure out what pins are what.. i am swapping an LS1/A4 in a 79 malibu, and woul like nothing more than ta adapt the C5 dash i bought to install, tach, spedo, gauges and all (perhaps the HUD someday ) i even bought the corvette underdash wiring to have all the connectors.. but i have been utterly unseccessfull in finding the schematics!
Look up some info on alldata. they should offer schematics for what you want. It cost's, but for something like your doing it might be worth it.
Old 11-11-2007, 06:28 PM
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G-body,

I won an auction on Evil Bay for a VDO gauge that says it can accept 500 - 399,999 PPM signal, but VDO has yet to answer if it will accept a square waveform. The guy who programmed the PCM already has it calibrated (tires and gears) for the correct 4000 ppm output.

If the square waveform does not work, does the PCM start throwing codes or act funny if an aftermarket meter is spliced into the transmission sensor output? Seems like some people have problems, some don't.

Like you, I'll gut out what I need from the gauge. The hard part for this one may be relocating the digital odometer to match the original gauge face.
Old 11-11-2007, 08:52 PM
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I thought I saw a box somewhere that excepts a electronic speedo input and has a cable drive output to drive an old style speedo.

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Old 11-11-2007, 09:05 PM
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Originally Posted by RE AND CHERYL
I thought I saw a box somewhere that excepts a electronic speedo input and has a cable drive output to drive an old style speedo.

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Correct, Cable-x. But if you can avoid that big box then it will be a much cleaner install, no? At least thats why I'm interested.
Old 11-11-2007, 09:11 PM
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I'm sure there are others out there, but I found THIS in a quick search.

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Old 11-12-2007, 09:41 AM
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I'll bet by the time you get done with the conversion box and the trouble, not to mention trying to fit it, an original gauge could be modified by Redline or North Hollywood Speedometer and take the PITA factor out.
Old 11-12-2007, 11:35 PM
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Originally Posted by CarlC
If the square waveform does not work, does the PCM start throwing codes or act funny if an aftermarket meter is spliced into the transmission sensor output? Seems like some people have problems, some don't.
That right there is the answer so far, I don`t have any personal experience with tapping the VSS as my speedo worked on the square wave signal, but I know that a bunch of people have tapped the VSS and some have problems while others don`t. I have not figured out why it causes problems only in some of the installs



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