Hi guys; 2000 Mountaineer. 318,000 miles. Trans works good; upshifts/downshifts smooth, no slipping. Engine good. No smoking startup or after. Pulls good. Idles good. Some valve lash adjuster noise. Whenever I come to a full stop, either in OD or D, the engine goes to nice idle (600 rpm) and then, 2 to 4, maybe 5 to 6 seconds after that, the engine starts to sound like it's lugging. You know the sound. That dull, kind of soft groaning/roaring noise when the engine's lugging and you need to downshift. If I shift into N or P the lugging goes away. Shift back into D or OD and the lugging noise returns. What's happening? Is the clutch not fully disengaging and that's why I hear the engine lugging? Something else? Thanks for your answers.