2005 LeSabre Transmission chatters slightly when shifting from 1st to2nd

I just purchased a 1 owner 2005 LeSabre with 22,000 miles on it that an older couple traded in on a new Lucerne and the transmission seems to have a very slight chatter when shifting from 1st to 2nd under normal or slow acceleration however, if I give it a little more throttle the transmission shift smooth as silk.

My buddy has a 2003 model LeSabre just like it and his does not do this so, I'm wondering if this very slight chatter (actually it's barely noticeable but present) is normal for a 2005 or something that I should be concerned about? Anyone have any ideas or suggestions?

It is possible there is a pcm reflash that will correct, this check with the Buick dealer.

ok, i'll check into it. thanks a bunch!