I am having an issue with my transmission. When my truck is in o/d and I press lightly on the accelerator and the truck downshifts I get a slight bumping and almost like a light shudder. If I press harder and get it to drop another gear it goes away. No DTC's and no drivability problems. This is the only situation when I notice this. I can pull a trailer or camper or just stomp it and I have no issues and it pulls like a beast. But if I just need to drop one gear for just a little extra power it starts to bump. Any ideas? Fluid and filters were just changed within last 2000 miles no issues with old fluid being dark or burnt smelling. Current fluid level is good and color is good. No leaks, drive line is good and tight, carrier bearing is tight. U-joints were replaced about a year and three months ago and I have been keeping grease in them. Slip shaft moves in and out nice and smooth. No issues when in 4WD low or high.