Thanks to Joe (bondocougar) for his amazing work and willingness to share the knowledge on this project.
One of the most requested changes to our cars is to make the stock digital speedometer read higher than the stock 85mph. Until recently it was not known if this was possible, but thanks to a spirited discussion (and lots of trial and error) on the message board, we now know that this can be done. This section will help you modify the electronics of your speedo to read to 199mph. Please note that this only affects the part of the module concerning the U.S.-calibrated MPH reading; when the module is set for KPH the reading will still only go to 199 kph.
First a little background on the stock speedometer. Remember that these cars existed in the 1980's, when insurance rates were very high, government regulations were coming in faster and faster, and speed-rated tires were only available on a select few vehicles. Therefore most vehicles from that era had speedometers that did not read past 85mph in the United States (with both analog and digital speedos). Owners were pretty much stuck with the stock configuration unless they added an aftermarket speedometer.
Now you don't have to! All you need to do is remove your instrument cluster, then focus on the middle speedometer module. You really don't need to disassemble the entire module from the cluster; in fact, the work can be done with the module still bolted in. All you need to do is find the W2 on the circuit board, and solder a jumper wire between the two contacts at W2. It's really just that simple! Reassemble the cluster and reinstall in the car, and enjoy!
The physical changeover of the speedo from 85mph to 140mph is fairly simple. But by no means does it imply that your car will actually attain those speeds. This mod is simply to make your car have a higher reading and does not warrant excessive speeding! Please see our disclaimer for more information.