Blinking overdrive light

I have a 2002 Ford E-150 with the Triton V8 and 75,000 miles on the clock.

And recently the light on the shifter that says "off" for the overdrive blinks while driving now. The trans works fine except for an occasional slippage which sometimes feels like a misfire.

i scanned the van at my work for codes, but nothing came up.

What causes the over drive light to blink?

I think this is caused by the lock up torque converter coming in and out at a certain speed. I would check all electrical connections and clean them with contact cleaner.
Ford transmissions have solenoid switches in the transmission which you can buy at the dealer. You have to drop the pan to install a new pack. Replace all if you are going to do it. I paid $65.00 on my 97 E40D for the 4 pack.
I had a problem which only happened when it was above 85 degrees. Later I talked to somebody who said some of the external towing transmission coolers were plugged. You can unhook the two lines and blow through with air.He said it was a ford problem I totalled my 97 and found a silverado about 3 years old with 3000 plus miles on it which I bought. One thing I found is 4 wheel disc will stop you much faster. I never liked the brakes on my ford.