Engine/Transmission (1994 - 1998) VSS signal type and shape

[ntsqd]

Our '96 2500 4WD came with the NP241D transfer case, which had a VSS and reluctor in the tail housing. I added a GV-OD and the used unit that I bought was set up to fit on an NP271 t/c. A Search found that the cost of the 241 adapter parts was the same as a good, used 271 so I had the stronger 271 put in the truck.

Fast-forward to now, when the GV-OD's reverse sprag has failed. I am removing it and will not be fixing it, but I would like to keep the 271 in place. Since trucks that got the 271 used the rear diff tone ring for their speedo signal the 271 has nothing for this. Ideally whatever I do will exactly replicate the original signal from the 241's sensor/reluctor assembly.

My net-wide searches have not found much good info on this topic, so I am wondering if this info is known here? Is there a known pulses per mile number, or other definition of this signal? Is it A/C or DC, what voltage, sine or square wave, those sorts of things.

As this is not a forum that I post on much, a little about me. Relevant to this topic, in 1987 I retrofitted a Toyota inductive pick-up and a Subaru reluctor to a Air-Cooled VW engine's 009 distributor and then again to a 010 distributor to gain OEM grade electronic ignition for the 1955cc ACVW engine in my fiberglass dune buggy. At the time the only really viable conversion was the Pertronix, and within my group of fellow buggy drivers we had seen more than a couple of those fail, which forced trail-side points replacements. I wanted OEM durability, and being a starving college student at the time my budget was nearly $0.00 The 010 distributor is still in that engine. I used the Toyota "Ignitor" and coil so that I had a matched system.
The converted 010: https://photos.smugmug.com/photos/i...dQ5xjr6VSdMZcxJM7HvdvJ6rcZ8/M/i-xZMkSXq-M.jpg
Where I hid the Ignitor for a more period correct look (inside that Mark Ten B housing): https://photos.smugmug.com/photos/i...ZKpr55VLVLcT2NGnP34vc2n3Ffc/L/i-vHhnkGH-L.jpg
Plotting the best path for this project is what I need help with, the aspects of getting it done are well within my skill-set.
Thanks for any help in advance!

 

[GAmes]

When I swapped to the G56 transmission I lost my VSS too. I installed a Dakota Digital SGI-5 Universal Interface. It is wired to the ABS sensor. The sensor has two wires. One wire connected to the sensor is a ground which I attached to the frame (ABS module was long gone). The other wire (could be red/violet) went to the input port of the SGI-5. If you still have ABS you can access the red/violet at the OBD port. The white/orange wire found under the dash in the big white connector is the speedometer wire. The output from the Dakota connects to it. DD no longer makes the SGI-5-C but as far as I know they still make an interface.

 

[ntsqd]

Thank you, that's a great data point. It tells me that one way or another I can get there from here. ABS is still functional, but an electronics savvy friend has postulated that with a fabricated diff cover it would be easy to add a second "ABS sensor" to feed a signal to the speedo system from the same tone ring. Fabricated simply because it is more rigid than the stamped part.

I am guessing that this is the product that replaced what you used: https://www.dakotadigital.com/index..._id=1192/category_id=-1/mode=prod/prd1192.htm

 

[GAmes]

I don't know that it will work. "Not for use with ABS sensors or systems." tells me it isn't like mine. No need to try to install another ABS sensor, the guy who gave me the wiring instructions had an ABS that was functioning. He just tapped into the red/violet at the OBD port. I didn't because that wire wasn't connected. I suggest you call Dakota Digital, their customer support is very good. Tell them that you need to accomplish the same as the old SGI-5 C universal signal interface using the ABS signal like I did.

 

[ntsqd]

I suspect that an ABS system needs a immediate signal, not one delayed by even a couple of micro-seconds, and that is why they say it's not for use with ABS systems. The processor may be fast, but it's probably not fast enough for an ABS.

Systems also don't seem to like to share sensors unless there is a dedicated circuit designed to share the original signal with multiple consumers. Just wiring them in parallel seems to degrade the signal's integrity or something. It's not too big of a deal to modify a fabricated cover. I planned to use the same sensor as the ABS system.

Heard back from DD. They say as long as I'm not working with the ABS sensor that the linked above part of their will get me there. Just for GP I'm going to ask to understand their avoidance of the ABS.

 

[GAmes]

They must have gone through several product changes. The box that replaced mine worked with the ABS sensor but I don't know what it's part number is. I can't think of another sensor that would work for you.

 

[ntsqd]

I wasn't clear, it will work with the sensor that the ABS uses, just not with the sensor tasked with generating ABS signal. A second, identical sensor will be fine. Just to figure out what the speedometer needs the signal to look like for it to work.

 

[GAmes]

An easier solution would be to disconnect the ABS module if you don't want to tap into it. I don't mis mine.

 

[ntsqd]

I've pondered that, but I think that I'd like to leave it functioning. At least for now. I don't rate the brakes as all that great, so maybe if/when I do something about that I'll delete the ABS. I had hoped that the H-B conversion would have made a bigger improvement than it did. It was an improvement, just not as much as I'd hoped for.