Bump/shutter When Cutting Off Engine

[turkish]

For the past couple of days, my truck seems to shutter or shake noticeably for a second or so when I turn it off. Seems like I can here a slight "bump" maybe on the last couple of strokes of the engine. At its worst, it seemed to shake the cab ever so slightly. This is a brand new 2010 Sierra with the 5.3. Anyone ever noticed such a thing? I did wash the exterior of the truck yesterday -- not sure if this is significant or just a coincidence.

 

Thanks alot.

[tanker4lyfe]

Hmm thats weird............