Have a 2001 F-150 with 74,000 miles on it and sometimes between 4th and 5th it bucks. Usually right around 40-45 mph. And occasionally between 3rd and 4th. It feels like it shifted too early and should have stayed in the previous gear a little longer. And on top of that the speedometer bounces around and sticks. But the truck bucks between 40-45 more than the speedo issue. No check engine lights or anything weird other than what I said above. I can't imagine the tranny being bad since it only has 74,000 on it. The only other issue Is the odometer flashes on and off but it still counts the miles so I'm not too worried about it.

 

Well the sensor on the rear diff wasn't the problem. Any more suggestions?