2002 Toyota Tacoma Pre-Runner my automatic transmission "thumps

2002 Toyota Tacoma Pre-Runner mileage: 9,000: Since day one, my automatic transmission "thumps" when down-shifting just before coming to a stop. If it does not thump when coming to a stop, it will do it when taking off from a stop. Tends to start doing this when normal engine temp is reached. Dealer says that it is no problem and that some trucks do this. Dealer says that they tried adding lubrication to the prop shaft joints to help lessen the thump. Dealer says that the Toyota Sequoia does the same thing. Is there a solution or is this just a quirk of these models?