OK I know I'm on the wrong board because I have a thirdgen but I'm looking for some info on the way vehicle speed sensors work on the 4l60e's and t56's. As far as I have been able to gather, my TPI computer (which doesn't have any requires a 4000 pulse per mile signal from the VSS to calculate the correct speed (for my speedometer, '89 T/A so it's electric, not cable). The VSS on a T56 from what I've read generates a 40 pulse per driveshaft revolution signal. I am trying to do this swap as inexpensively as I can, so I was looking for an alternative to buying a conversion box (ie Dakota Digital SGI-5 etc).

1. Do A4 or M6 cars have any inline conversion (or processing) box that alters the signal before it gets to your PCM?
2. Do any other vehicles with a 4l60e have what I'm looking for?
3. What is the VSS output of the T5 from 93-97 v6s?

Any information on this would be greatly appreciated. Thanks!

 

You'll have to ask this on www.thirdgen.org, it has been covered there a million times. Most people will say that using a digital box is the only way, but I've heard you can do it through a PROM if you know what you are doing. I've also talked to professional PROM burners who say it can't be done that way, so who knows. I've never gotten my digital box to work with my T56 so I wish there was another way out there.

 

thanks for the reply, I've already posted on thirdgen.org and I've searched as well as I could on there, and came up with nothing. I believe it can be changed through TunerCat on speed density cars, but I'm running a mass air flow sensor. I'm beginning to think that my only options are a programmable speedo or a digital conversion box.

I know that third gens have a yellow or blue? conversion box that converts the A/C square wave signal or whatever it is to a D/C signal the ECM can understand, and was hoping that someone knew of one of these on LT1 cars that might do the same that would work on my car. I'm pretty sure 87-92 firebird (electric) speedometer gauges are interchangable with 93-97 gauges, and was thinking that just maybe 87-92 ECMs and 93-97 PCMs need the exact same signal to show correct speed, which would require some other type of conversion box as stock equipment on 93-97s.

Are you having problems with the car stalling when coming to an idle or with your speed limiter kicking in? Do you have your VSS hooked up at all or totally disconnected? I've been told that Dakota Digital's instructions are worthless and that there's an out3 signal on the conversion boxes that is what you have to patch to your ECM. I've read a few cases where that was the problem. Hope that helps. Otherwise, is your digital box for sale? hehe

 

I had my VSS connected and just had my speedometer reading 1.5x too fast for the longest time. I recently did a clutch and flywheel install and decided to finally try to get the digital box working. I have a good wiring diagram from TGO that is better than the Dakota instructions, but it fails to show what the OUT3 is supposed to get wired to on the ECM. It is pretty easy otherwise, one of the VSS wires goes to Sig In, one goes to ground with a ground wire, and then a 12v accesory wire goes into the power slot. I just don't know where/what to connect the OUT3 to. I wanted to avoid the whole thing and go the tuning route but no one can do it. So now my VSS is just unplugged because that happens to be the way I left it after a few hours of messing with it. Idle is fine, speed limiter is programmed out. It just reads 1.5x too fast and accumulates mileage at that rate too when it is hooked up.

 

I am in the process of putting a 6-speed behind a 350 tpi and need input on what I need to relay information from the T56 to the VSS?

 

http://www.skulte.com/T56.html

If that doesn't answer your questions there's a ton of extra stuff on www.thirdgen.org just search for it and you'll find it