I have a 1993 F150 4X4 with a 302 mated to an E40D transmission. Truck seems to work fine till I come to a hill and then it starts to vibrate and shutter part way up the incline. Thinking it was the motor misfiring at first I changed plugs , cap and rotor. Also put dielectric grease on the plug boots as this was recommended procedure for these year trucks to keep them from misfiring. Turning off overdrive has no effect on the vibration and shuttering. Changed out transmission filter and 8 quarts of fluid related to dropping the pan. Added anti-shutter additive with no change in vibration. Am I slipping in third and fourth gear or is it something else? I was always told the E40D was pretty much bullet proof. Thanks for your help.

 

sounds like torque converter shutter.