It sounds like a missfire. I have to say, without the check engine light, it makes it difficult. Have they checked things such as the catalytic converters, crank sensor, vacuum leaks. Also, do they feel it could be the transmission? Try this. Put the truck in 2nd gear and slow down to the speed that you feel the problem. See if it still does it and let me know.
Sunday, October 3rd, 2010 AT 9:43 PM