speedometer works intermittently - sometimes more or less ok, but sometimes the needle flaps about bizarrely, or says I'm going 40 when I'm keeping up with the other cars going at least 60mph on the freeway.

What is your question?

Some days it seems OK, but have problems on other days for no rhyme or reason. It seems to indicate a bit slower than I'm actually going, if the 'your are going...' signs you occasionally see are accurate. I recently got a new transmission (I see in some of the discussions that there's a sensor on the trans, so thought I'd throw that in). I drive a LOT, but since I've spent a fair amount on money on the car this year, I would really like to fix it myself if possible.

What makes this problem better or worse?

Not sure, it seems random. Sometimes it acts up, sometimes it doesn't.

How long has your 2002 Kia Rio had this problem?

A few weeks (I have traffic court coming up this week for speeding because of this. Speed trap, late at night, no other cars to guage speed. *sigh*)