I actually have a bad second gear, per the previous owner. It has the common jumps out of 2nd gear on decel. It's why I bought the entire assembly from the guy. You can see the Borg/Warner overdrive unit hanging off the back of the transfer case and connects to the driveshaft. That required me to replace the driveshaft with a shorter one the seller even provided! Here's a write up on how the BW overdrive unit works. Would have preferred the Warn/Saturn, but at $1K, pricey, plus I still have a bad trans. http://www.fordification.com/tech/overdrive.htm Here's an old picture of the truck when I first got it 2 years ago, pretty much looks the same.