What's that clunk?

I’m starting to notice a clunk happening more and more often when I’m driving. There are several different situations that it happens. If I coast the car for a few seconds and the hit the gas I get a clunk that I can feel in the seat. It feels like it’s coming from behind me too. Is this because the gears are just worn down and there’s a bunch of slop? It also happens occasionally when I’m shifting gears as I’m letting the clutch out. Doesn’t happen when I’m extremely gentle with letting the clutch out. It wasn’t as bad a couple weeks ago but then after I did a 3k rpm launch it seemed like it became more prominent. I’m pretty much convinced my transmission is going to take a shit on me sooner than later because all the mounts are new, I just installed the LSD with new diff fluid, and the diff mount is tight. I can’t think of anything else as everything is torqued down nice and tight. What’s the worst case scenario if my transmission goes out? Again for those of you that don’t know, I’m competing in a half mile side by side roll race at the end of June. The race starts at 50 mph so the speeds I’ll be hitting are going to be quite high. Am I risking destroying my car because of the transmission. Thanks in advance, I appreciate any insight.