My 2000 4.7 D w/ 137k on it has lately been driving weird. Transmission is shifting fine when accelerating from a stop, but when I'm at 35 mph and hit the gun 3/4 to downshift to a lower gear (not the lowest), the shift feels soft, and it does not over rev, but you can hear the rpm's going up and down a little bit. It still has lots of power from launch, and shifts clean from there, but just to pull out for a pass, it lacks power or something is going on in the tranny that hasn't let go yet. Any help would be appreciated as I am going to be doing a lot of driving over christmas and need my truck.