Transmission or Torque Converter or ???
 

2007 Expedition with 109k. While driving at a constant speed between 35-55 mph, I get a shuddering like sensation through the cab of the vehicle. More pronounced while climbing a hill.

The feeling is that of a wash board dirt road or rumble strips on the sides of the road. I get another sensation/noise from being stopped on a slight hill and letting the truck roll backwards while in drive. After the hill roll back, still in drive, press the gas (less than 1000rpm's) slightly while going uphill and its as if something releases. Not a loud sound at all. Still felt through the cab.

All fluids changed, tranny, t-case, rear & front diffs. Plugs changed at 101K, and cop's changed 108k.

Any help greatly appreciated.

could be anything, I'd not think transmission first. Could be CVs in the front or rear end, could be the brake rotors out of round and warped. Could be a bad ujoint. I'd check the wheel bearings and other suspension parts too while I was at it before I went pulling a trans.