On a long road trip today, the Burb seemed to be hard shifting at low speed. Kind of a clunk sudden jerk feeling versus a smooth shift. At higher speeds I didn't notice it. I noticed this behaviour once before. The problem seems to come after driving a bit. Slow acceleration seems to be fine, it's the middle acceleration speed that seems to trip it up, and only occasionally. I'm thinking of having the transmission fluid flushed. Any insight would be appreciated.