Rear end making a ka pow noise .

Hello, The first thing I would check is for a carrier bearing (would be on the driveshaft). If the carrier bearing is good, look at the mounting hardware for the rear differential. If everything looks good, stays tight, and makes no noise under pressure, check the driveshaft and axle's for play as well. You may also have bad shocks/struts. Lastly, these vehicles, along with their Tundra sibling, are WELL known for rusting in the rear cross members, which could allow some movement of the frame under load. I am assuming this happens when you put the vehicle in reverse/drive from park/neutral, please correct me if I'm wrong.