theres a hard thump coming from the back of my jk when I hit bumps in the road (which i think i've narrowed down to the back passenger side), it just started recently. Recent mods i have done are 33.5 inch tires and wheel spacers on stock rims and cut the fenders (in which i had to remove the splash guards). Any tips would help if its something i can look into myself saving me the trip to the dealer.

 

First thing I would try is get under your Jeep and look for the odvious. Loose bolts, any signs of things rubbing or bottoming out. If something was not tourqed down to spec, they may look tight, but loosee enough to cause issues. Grab hold of the various parks, givem a good shake. If you have access to a lift, put the Jeep in the air and flex the susspension, simulate a bumb as you say.

Good luck!

 

Possibly a loose shock, they will bang pretty loudly if they are loose.

 

I have a 2010 jk and to take a stab in the dark it's probably ur shock bushings. I had the same problem, one bushings had split and come off. So any little crack in the road and I would get a pretty good thump / knock. But keep in mind there's a lot of stuff that could cause that(such as a body mount bushing to a BJ to any other bushing. My advise get it checked out and let us know what it was.