I have a 1995 es 300 w/ 230,000 miles and after driving for about an hour, i parked and the speedometer needle just started bouncing from 0-140-35-24-100 etc...
I noticed for the past year that the needle would drop down to zero from the 10 mph mark while stopping. I hope this can be fixed without replacing the entire unit.

 

The bouncing needles are usually a sign of poor grounding. I would check all your vital grounds for the electrical system. In my old lex, the fuel needle used to bounce around, and sanding/re-grounding the grounds fixed it.

 

hmm, i decided to ignore this problem with the speedometer as this didn't occur very often. However, I was stopped at an intersection, the needle went crazy and my odometer started going...5.0 miles added
should i replace the speed sensor???