2003 2wd with 105K miles. Warm or cold, when shifted into Drive or Reverse the selected gear partially "engages" and then suddenly fully finishes engaging. The problem has been present for about 15-20K miles. Transmission fluid and filter have been changed. Did not see any foreign material in the pan, fluid, on or the magnet. Once first is fully engaged, ALL other gears are fine and the transmission shifts up and down perfectly. Thoughts?