My 2011 DC does this. Almost like you were getting a little crazy with skinny peddle for a moment. I have had this happen with other vehicles and just chalked it up to being the tranny trying to catch up to the rest of the drive train.My brand new 2017 SR5 DC does that...no clunk, just a delay in power being applied to the driveline resulting in a slight sudden increase in engine RPM that's quickly knocked back down to normal when some drive line component suddenly engages and the truck gently lurches forward. I think it's the automatic transmission being lazy, and delays the shift to 1st gear until you seem to be fully determined to start forward again. Either that, or as someone suggested on an earlier related thread, it's the torque converter being unclear about when to be locked versus unlocked.
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