2000 SPI Auto Transmission Problems

I have a 2000 Focus SPI with the auto transmission and around 165K miles. Recently, the transmission will not shift out of first gear until around 5000 rpm OCCASIONALLY. Most of the time its fine. When it's acting up, it won't even shift into second gear even if I move the shifter into 2 (which should lock the tranny into second and make it stay there). And then there are times (when its in this bad mood) when I push the pedal to the floor going about 25 mph and it doesn't want to downshift out of 2nd once it finally gets into it.

SO what I was wondering is if anyone knows if I have a sensor problem (No check engine light is on), maybe a bad solenoid, or what?? It's aggrivating, because it doesn't do it all the time, usually only in heavy stop and go traffic, so I want to believe it's not a hard fault in the tranny.

ANY HELP OR SUGGESTIONS WOULD GREATLY BE APPRECIATED!!!

sounds like a speed sensor to me, has your O/D light even came on and flashed?

Nope, and there is a test you can do to make the trip odometer display your speed, and this shows that the speedo sensor is fine. I figured out that when the car is acting up, you can shift into neutral and turn the switch off and then back on and it'll shift fine, which only makes me more confused!

speed censor doesn't measure the speed of your vehicle, it tells the tranny when to shift according to the speed you're at.