if its clunking when you put it in gear...yes that would be a u-joint.
if you feel it when you take off...then you more than likely need to grease the slip yoke on your driveshaft by pulling out the driveshaft at the carrier bearing and slapping some grease on it and reassembling.
Is it as simple as it sounds to pull the driveshaft from the carrier bearing because i get both when parked putting into gear and if driving and letting off the peddle then pressing on it again?