Mine is doing the exact same thing. Same truck as well except mine has 284k.. PREV owner did not love her and she sat for a long time prior to 6 months ago when I got her. Replaced all wheel bearings and both calipers on front.. Rotate tires and filled tc. She was low so I drained and refilled but fluid was black. Couldnt tell if there was metallic shavings due to the pan I was handed. I wasnt aware there was **** already in the bottom of the pan before I used it. She doesnt drag as bad now when coasting that's for sure. Ps res is full. Black, but full. Shes old and prob never went under the knife in years. Clutch n brake res are full. Flushed brake system as well. Clutch feels fine surprisingly. But I can sometimes hear the "denture" sound in drivethrus where sound echoes if I pump the clutch without shifting. When I first test drove her I assumed rear diff was low on fluid. When I got her I check it through vent hose and she wasnt low enough for the amount of lip I'm getting from her if ya know what I'm saying.