Hey

I have one last issue to iron out with my LS1/T56 swap into my 1991 RS that has a 3.1L 700R4 before.

Anyways, when I turn the car on and Im in neutral my speedo reads 80 km/h. Also when I come to a complete stop it does this. When I rev in neutral the speedo will go up to 160 km/h. This is annoying because my odometer keeps going up when Im sitting still.

When I start driving, the speedo begins to work normally but its reading a bit low (ie it reads 45km/h and Im really going 50). I have the Dakota Digital box and I think its wired in properly. How did you guys set your dip switches? What else could be wrong here? Thanks!

Kubus

 

You didn't need the dakota digital box for the speedo since yours is a '91 model with an electric speedometer. You could hook the speedo output wire from the PCM directly to the 4000ppm input wire where the VSS box is at and it will work just fine.

 

are you 100 percent sure? why did everyone say i neeed one before?

 

it's not needed but you would need to change the calibration in the pcm for it to read correct with your gear ratio and tire size.


if you do a search alot of the t56 swaps req. this when only using the trans from a lt1 car. since you don't have the lt1/ls1 pcm to change it.

often times if you use your stock speedo wires to the trans it will act like you are describing since they run near several things that creat interferance. alot of people end up running new wires.

 

The LS1/LT1 PCM has an output for Speedometer that outputs a 4000ppm signal. The 3rd gens with electric speedo's have a VSS buffer box that takes the signal from the tranny, and converts it to the 4000ppm signal. Since the LS1/LT1 PCM has this output already, all you need to do is hook that wire up to the green or tan wire where the VSS box is and it will work. Now like 350TPI stated, you will need to have it tuned to change the gear/tire size for the speedo to be accurate, or buy like a Hypertech programmer which will do it as well.