2000 caravan jerks hard and the spedo drops at highway speeds.

Hi, my van just started to have this issue today with jerking real hard like its dropping a couple of gears while going between 50-60mph. It is a 2000 with the flex fuel 3.3L 4 speed auto.When this happens the spedo will go from 55mph to 40 instantly while keeping a steady speed and it feels like the tranny is going to rip right out. This will happen every 5 to 10 min but go back to normal driving after 3 sec and has not popped any codes. It runs like a top and all fluids are at the correct levels. I have to commute 50 miles a day to work so i really need to figure this out!!! Thanks, Robby

If you're saying the speedo is erratic along with the jerking it sounds like a classic output speed sensor failure. That would be a good starting point (~$25) but just be aware it could also be wiring or the TCM (tranny computer). Here's a pic: http://ww2.justanswer.com/uploads/dodgetech2875/2010-03-30_041602_41te.jpg If you decide to change it check connections first for corrosion and security. The sensor is used by the speedo as a speed reference and for shift scheduling by the tranny.