c1236 Rear left wheel speed sensor input missing. I was driving down the highway the Speedo dropped down 20-30 mph from 65 the truck kinda shuttered and the abs light came on. I stopped and pulled the code cleared it and it happened again a few miles up the road. This was after about 2 hours of driving. I thought these trucks just had one sensor on top of the diff. Sports this sound like that sensor is going out? Or do the 05's have two sensors in the rear? I'm 250 miles from home but would rather change out for the ride back. It's not a good feeling when it happens. And prior to this everything works on the truck as it should and no dash lights I want to keep it in order. Thanks for any input.