My '97 Ford Explorer may need a tranny...but I am trying to avoid that (something about the high cost). Details: Driving down the road, minding my own business, and wham...the O/D light starts to flash. After a restart or two, it stopped. Ok, minor hiccup, no problem. Wrongo. Check Engine Light came on. Now, i don't know the exact code, as the AutoZone dude just said I needed to replace my speed sensor switch. $15 got me a new one, and I was on my way. Two days later, O/D flashes briefly, then stops, and Check Engine Light is back on. This time I get to see the exact code P0720 Output Speed Sensor Circuit (probably the same as the first time). I don't have a heavy foot, but as I drive, the RPMs will occasionally jump as the tranny shifts. It is very momentarily, and other than this (and a noticeable decrease in gas mileage), all seems well. I've read as much as i could find on P0720, some suggest replacing the solenoid. Forgot the miles: 137K and going strong!