Knocking sound after slammage??

So after slamming the rear down as far as it will go, which imo still isn’t that low for an s14, and adding RUCAs there is a variable clunk that appears when accelerating which seems to speed up as I go faster, I believe it is the axles (which have 312,000 on them), does that make sense? doesn’t make teh sound if I just coast,
jacked the rear wheels and ran it that way but seems it only happens when its under load. There’s no crazy angle on the axles when on the ground, pretty much straight from the diff. When i move the axles side to side it sounds exactly like what i hear in the car.
any thoughts? its so annoying…