2000 Chevy Silverado Massive Clunk upon Acceleration

What in the heck? I was taking my son to hoops this AM, and made a turn onto main road, as soon as I accelerated it made this CLUNK sound throughout the whole truck and it felt almost as if we had been hit.

Nothing in rearview mirror so pretty confident the engine is still in there! I continued on and it became more frequent, most noticeably when you are going, does not happen when coasting or at a stop, only under a load. So it clunks very hard and your movement feels like it skips a beat as if power delivery is momentarily suspended for the duration of the clunk.

Does this read like Tranny or Rear Diff or or maybe? It seems pretty radical a sound to be u-joints but who knows.

I’ve done a lot of auto stuff, but this is my first foray into the clunking unknown.

I am new here and am starting off with a beg for help!!

Thanks, Keith

I’d look at the motor mounts right away. There are only 3 usually, one on each side of the engine and one under the tailshaft of the transmission. Look at the engine while its idling, then have someone rev it in neutral or park. It might jump quite a bit, or twist. They are not a huge deal to replace and they can make a big clunk when they are broken.