used to feel it taking off from lights and thought it was the converter.feels like a shuttering or vibrating . now the converter is new (triple disc and fresh trans) and still does it the same and i notice while pulling a load (26000lbs) my guy cruising at about 1500-1600 and i can feel it .almost feels like when your in 6th and should be in 4th . soon as i drop a gear and get it into the 2000 rpm range seems alright . could it be a bad injector or mulitple?