Recently I completed a 3800SC and 4T65E swap into my 86SE Fiero. I ran into a small snag once I got the swap running and hopefully my solution will be worthwhile to people using either a Pisa or custom dash.
The problem was due to the fact that the Pisa dash is essentially only for a manual transmission. End result is I now had an auto and no indicator to show the gear I was in.
The schematic (for a 98 GTP – verify everything against your own schematic) shows that 4 wires come from the transmission park/neutral switch and go to the PCM and the instrument cluster to indicate the gear selected. I originally was going to figure out the binary for each position, decode it then output it to an indicator I would build with 7 LEDs in it.
![](https://images.fiero.nl/2010/schematic.jpg)
I did make a schematic for that – a demultiplexer chip and a 5V power supply would work – but I decided there may be a section of the instrument cluster I could cut out that may make my job easier. I went to the junkyard and found a 97 Grand Prix and removed the instrument cluster. Following are two pictures of the cluster I ended up using.
![](https://images.fiero.nl/2010/DSC00786.JPG)
![](https://images.fiero.nl/2010/DSC00787.JPG)
Notice on the back of the cluster the small circuit board. This is the one you need. There is a ribbon cable that runs to it with 7 traces on the board. The wires are the 4 mentioned earlier, +12V, ground and a line for illumination. When +12V is applied to the illumination line, the LEDs will dim to the night mode. I removed the ribon cable connector and soldered wires in place of it to hook into the Fiero/4T65E system. Ignore the wire colors in the picture. I just used what I had.
![](https://images.fiero.nl/2010/DSC00789.JPG)
![](https://images.fiero.nl/2010/DSC00791.JPG)
[This message has been edited by AlanD (edited 10-07-2010).]