Flashing O/D light and Speedo quits
 

I bought a 92 LS in Houston and drove it to Ohio last weekend. It ran well but a couple of things happened that I don't understand. About 3 hrs. into the trip the O/D OFF light started to flash, about 1/2 second on and two seconds off. It did this for about 30 minutes. When I pressed the O/D button on the shifter, the light stayed on steady. When I pressed it again the fashing pattern started again. I stopped for food and when I took off everything was normal. About an hour later, I was on cruise at 70 when the cruise suddenly quit. I looked at the speedometer and it was on zero! I drove using the tach to maintain 70 and occasionally the speedo would jump up to 70 and drop just as fast. After about 30 minutes everything returned to normal. Next morning these things happened a few more times. Could it be a bad connection at a plug? If so, where is the plug. Anybody have an experience like this?
Also, it's about 10 degrees out tonight and when I rode the passenger side there is frigid air coming out of the right vent and it's cold by my right foot. Driver side is fine. ???

My best guess at the situation is a bad or loose speed sensor.
Now for the O/D light flashing, this means the transmission is picking up a code...Something is wrong.
you should get it diagnosed, preferably when the car is showing the problems. But don't worry, they're probobly small glitches that won't rip your wallet.