VSS Ford 8 PPR to Chevy 2 PPR for TBI etc....my version

I decided I want to implement VSS on my TBI projects and the old 747 needs 2 ppr on the speedo cable, or 2000 pulses per mile, and since north american cars all seem to use the 1000 speedo cable turns per mile, you need 2 pulses per rotation of the cable. The only off the shelf method I found was to buy a Dakota Digital adapter or similar magnetic or optical sensor, which is pricey and shipping and delays and blah blah blah. Being in Canada, anything that has to come from the US ends up costing about double the listed price, so I try to use anything local that I can. I was unable to find anything suitable from the local wreckers so I decided to use what I have on my AOD tranny, the 8 ppr magnetic VSS which interfaces just fine with the Ford ECM, but doesn't work with the GM ECMs.

I dug into my archives of valuable electronics that I have been collecting for years and figured out how to get the 8 ppr divided down to 2 ppr. I used an LM339 comparitor and a CD74LS74N dual D type flip flop, the LM339 changes the sine wave from the AOD sensor to square wave, then the flip flops are configured to each divide by 2, cascaded they give us a divide by 4 output, so 8 in gives us 2 out. Cool! I will simply build a little breadboard type PCB and house it in an old DRAC plastic housing and put it under the dash next to the ECM, should work just great, plus I can still use the cable drive for my old 49 Ford speedo.

If you want any details about the circuit, let me know.

Cheers

https://www.dropbox.com/s/2mm4nwm688..._1707.avi?dl=0