I have a 99 Expedition with 302k miles. It has a slight stutter when accelerating. For example, when you give it the gas to accelerate the truck stutters/slips. It feels like a misfire but I've replaced all plugs and COPs plus the truck has never thrown a misfire code. I've serviced the transmission and the the transfer case (drain and fill) to no avail. The truck runs fine other than this stutter. I do have a leak where the drive axle exits the transmission. I'm assuming there is some seal that has gone bad. Could this be the cause of the my stutter? Also, does anyone know the effort to replace this seal?

Thanks in advance.