I own a 96 cavy with 127k about 2 months ago it developed a random knock. it sounds like someone it hitting the bottom of the car with a rubber mallet on the passenger side. its decreased in frequency but I still hear it about twice a day at random times

if it is a dull noise it and happens under deceleration or at idle it could be a wrist pin connecting the piston rod to the piston itself.

What motor? The Ld9 2.4L is notorious for throwing a main bearing on a certain piston. I forgot which one is was for sure, maybe # 3?

yes, #3

no its a 2.2 happens mostlly when shifting from reverse to drive or vice versa. sometimes when letting off the gas after accelearating andd rarely when braking.

Sounds more like a transmission problem than engine related issue.