A bad gear in the Speedo will make the odometer not work, that's it as far I know about.

With the upshift light double check all your grounds just to make sure one of them is not loose. Most of them are on the center console, but there may be others up in there.

If you can jiggle the connector and change the results that points to loose connections on the harness side connector and or badly corroded or worn contacts on the back of the cluster. Unless you got a wire pinched at some point I would doubt a short. Time for an old Elect Tech trick, find a good Pink Pearl Eraser and give all those pins on the back of the cluster a good buffing to raise a shine. Do not use any hard abrasive on the pins! You do not want to scratch up the pin, once the copper under the AU is exposed the corrosion will really take off. The gold or nickel used the plate the pins was ment to be a barrier to protect the copper. What you gain in the short run will bite you harder in the long run if you scrape in too far.

On the connector side look for any pushed out pins, and for deformed or opened up contacts. You can take a small tipped pair of pliers or a jewelers screwdriver and close up the contacts just a bit. Getting carried away will result in a crushed pin and that's no fun.

You may want to consider a donor PCB off another cluster or splicing in a new connector, depending what you figure out during your trouble shooting. The PCB is not hard to do, just a lot of small screws and take your time. The Harness side would be a pain in the buttocks.

Good Luck,

PT