Technical Tremec TKX VSS - speedometer calibration

I have a 62 Ford Fairlane, to which I replaced the C-4 auto with a TKX 5 spd. My speedometer, Omega Kustom, was using a two wire speed sensor with a gear drive on the C-4. The TKX has a VSS (magnetic type) for the speedometer pick up. I havent had any luck with manual calibration to which you drive a mile, setting the speedo. This results in my speed reading being about twice as fast as road speed. With manual input of the pulse per mile (around 35000), the speedometer barely moves. My thinking at this point is to drive the car at a set speed (GPS reading) and figure out what input i need to have based on what value I currently have in the speedo. Anyone got any input?
Trans TKX replacing a C-4. Had 16 tooth gear to pulse sending unit
Drive ratio - 3.50
Tire dia - 26.6 & 759 revolutions per mile

 

Take a look at Classic Instruments SN74Z interface. Contact them and discuss your conversion.

 

I read through the instructions from Speedway's website. At the bottom, there was a sensitivity setting. Have you tried changing that? I have had electronic devices take a "set" and not be able to reprogram them before. That might be what has happened. As I remember, you can connect an ac volt meter and measure the pulses from the vss. Doing so would verify that it has a good steady signal. I did that with the vehicle on jack stands so that I didn't have to be concerned with running off the road while watching the volt meter.

 

Is the new VSS a three wire?

 

two wire

 

I thought maybe we were dealing with sein wave vs. square wave but that's not it.
The interface from Classic is all I got.

 

Why didn't you just move the C4 sensor over to the TKX? The TKX will accept either type of speedometer output, at most you should only have to change the gear depending on which side of the C4 the speedo opening is.

 

i think out of the box initial start settings are 16000 pulses per mile - i.e. the aftermarket guages come pre set at 16000 pulses to match a gm transmission tone ring or reluctor - i would start there.
put a ground strap from the transmission to traverse the transmission mount to the frame
just in case they painted the mating surfaces of the transmission, or the block - plate or sandwich plate or what ever you call them.
make sure the reluctor is free of metal debris

 

UPDATE: FIXED - I tried reversing the polarity on the VSS sensor, just to see if any different results where to be had, which changed nothing. I ended up manually entering the input value for calibration and after several attempts I finally hit the right one. Speedo works like it should!