Hey guys what are you all doing for a speedo hookup to the stock speedo running a 4l80e with a Holley HP efi system?? I'm using a manual controller for the transmission currently. Is a Dakota signal box my only option??

 

Your 91 Z is electronic already, isn't it? Why can't you go directly from the 4L80 to the speedo? ....either way, if ya wanna run it through the Holley HP, I'm pretty sure you'll need a proper hall-effect sensor on the 4L80 end and the Holley add-on harness on the ECU end. The HP has the capability for it, but isn't wired and set up for it as it comes.

 

Yea it's a 91 and electronic speedo but the speedo needs to see a 4000 ppm square wave signal which I don't think the 4l80e does?? Not too sure still looking around for a solid answer

 

OK gotcha. ....I was a huge fan of the Holley HP system, but if you find an efficient way to go from the transmission right to the speedo, I think that's what I would do.

 

I suppose you could do the same thing as I did with my T56. Just use the appropriate tooth count (40 tooth?) in the "Pulses to Average" field.
Post #179, https://www.thirdgen.org/forums/ltx-...ml#post5821648

But if the speed sensor is 40 tooth, then it is already putting out an AC wave that happens to be a nice round multiple of 4000 ppm that the speedo wants to see. That just seems too convenient like we're missing something really easy here.....

HP EFI does not have a transmission add-on harness (you should know this!). There is a speedometer output option in the software but it is tied to the trans ICF and depends on inputs from the trans harness. No can do with HP EFI.

You could possibly try setting up a PWM output but I'm not sure whether it would drive the speedo.

 

The generic "add-on" harness DOES have a input for a speed sensor.
The HP CAN be wired for a speedo using a hall effect sensor.
Can the add on harness be used to pick up that hall effect sensor? -I don't know. Perhaps the HP has to be wired another way. I didn't need any of this as I was purely mechanical from TKO to 89 Iroc cable speedo.

 

That's nice but he didn't ask about that.

 

Hahahaha!!