First post, yes I've searched...

But even after searching im sorta confused...Just purchased a 1990 Trans Am w/ a 94' Z28 LT1 w/60,000 miles installed in it......transmission is a built 700R4...shifts real solid...has 60,000 too....

Question is....everything is working exept the Speedo and the Odo....not positive, as I have not checked...but Im not sure as to whether the VSS is installed or not....but the car runs awsome...no stalling what so ever...so im (assuming) it is installed....sooo...how exactly do I get the speedometer/odometer to work???.....any semi-easy way??....the LT1s computer is under the passangers footwell carpet...so it is easy access.....

and yes..I really would like to keep the 700R4 until its gone...because apperently right after the engine swap the same week the trans was destroyed and really built up for this engine....so does anyone out there have the 700R4/LT1 combo and a working speedometer??....I know dakota digital has that universal speedo thing.....is that all I need?

 

So far, everyone that has put a 700R4 behind the LT1 that I know of, hasn't gotten the speedo to work....it has to do with the pulses coming from the 700R4 which is a bunch, like 40,000 and getting it down to the 4,000ppm that the speedo uses which is the stock output from the LT1 PCM.

I believe the Dakota digital box is the only option to do this using the original VSS in the 700 and the speedo you have in the car.

 

You should be able to use the dakota box to convert the signal going from the 700r4's VSS into the LT1's PCM. The LT1 PCM's speedo output should already be correct, just hook up its output to your speedo feed wire and all will be well.

*This is kinda similar to what you do when you put a T56 in a TPI car. You have to run a dakota box to convert the signal going from the T56's VSS to the TPI's ECM... the TPI ECM will of course already have the correct output to the gage just like your LT1 PCM will have the right output for your speedo.

**For my LS1 swap all I had to do was hook up the LS1 PCM's speedo output to my speedo feed wire... works perfect just like the factory and I can "tune" my speedo by changing gear ratios and tires sizes in the LS1 PCM. It's almost all too easy.

 

i've been working on the LT1-700R4 speedo thing. I think i have it all calculated out but only one way to find out if i really got it figured out. I got my LT1 finally running tonite but i kind of need exhaust now. So, it might be some time before i get to test the speedo.

My way of making the speedometer possibly work involves re-programming the LT1 pcm. This requires tunercat tuner: $70, tunercat EE def file: $20, aldl cable :$90 unless you buy the kit and solder it yourself then its $45, and a computer with a serial port. So, you're looking at $70+$20+$45=$135 at the cheapest if you have a computer you can relocate to your garage.

The $85? sgi-5 box might be a better option for you. For others who already have the stuff mentioned above, or if you plan on doing tuning by yourself in the future, you may want to wait on buying that sgi-5 box...