Using abs wheel sensors to replace VSS

I have a stock 2002 Chevy Silverado 4x4, 2500 HD, 6.0 L - 4L80E.

I did a transfer case swap with an older transfer case (94 ish?), and haven't been able to get the speedometer to work correctly. I have no idea if the transfer case I got had issues, or if it uses a different type of pulse (square wave vs sine wave).

The truck does a decent job of shifting considering it doesn't have a speedometer, so I assume it is getting some information from the front wheel speed sensors. (however it does shift hard)

I hacked into the ABS harness for it and my speedometer read at aprox 1/2 of what it should (maybe 17/40 if I were to guess?). My thought was to change tire size / transmission gear ratios via HPTuners.

I know this isn't proper, but is there anything it is going to hurt? (aside from losing my ABS, and potential troubles with wheelspin).

Attachment 46625

Also is there a better way to do it? They seem to give me quite a few options. - changing the VSS pulses, - VSS output pulses (not sure the difference? - or change both) per mile - rear end ratio - trans rev/mile.

If I "trick" hp tuners into doing it for me, by telling them I change my tire size( and don't scale tables), it maxes out the trans rev/mile and changes the top vss pulses.

I can just play with it and see, however there is a warning I can't fully read and the helpfile doens't duplicate when I hover over vss output/mile, saying not to set this too low as the PCM may .....

Also I thought there may be some things that I hadn't considered? I believe I will still have my passenger side front wheel speed sensor, so I'm thinking it will just think I have a bad drivers side sensor, which is something I figure the truck can handle.


Thanks in advance,

So in case anyone else is reading this to learn - I ended up changing the VSS Pulses per Mile (from 111,684 to 36,000) in my case, which brought the speedometer up to within 1%. However the transmission was shifting at very high rpms (at 80 km/h I had to let of the throttle hard to get it to shift into 3rd). I took the same 1/3.1 ratio I used for the speedometer and applied it to my trans revolutions/mile (2789 to 900).

After a few test drives everything seems to be working the way it should. I will update this thread if I ever find a problem with doing this.

I have also attached my upgraded tune to show for anyone who doesn't understand what I did.
Attachment 46654

I also learned by myself that you cannot do a search for 3 letter words such as ABS or VSS (at least from the top right corner).

There may be ways around me turning off the ABS sensor (by splicing into right front wheel for example). However, with every way I think of, I imagine a scenario where I would want them to work differently then they would want to work -> ergo, not safely.

i what pin or wire did u hook up ur vss too on the stock harness

Quote:

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Originally Posted by BoostedVic

i what pin or wire did u hook up ur vss too on the stock harness

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Can I grab off of a wheel speed sensor instead of pulling the whole transmission back out?