2003 silverado lowered alignment issue
 

Hello, I have an 03 chevy silverado single cab 2wd v-8. It has been lowered 2" in the front with spindles and 4" in the rear with shackles. I have changed the rack and pinion all the tie rod ends, new upper control arms (ball joints and bushings), new lower ball joints, tires are new and have been balanced twice. It has 18" aftermarket wheels with some 285/50r18 tire's. The truck only has right at 70,000miles on it. I have the alignment close but when I go over railroad tracks even at low speed it sounds like something is very loose especially on the passenger side, but I can not find anything loose. I have greased my intermediate steering shaft, with no change. I also replaced the shocks with some monroe gas charged shocks. I am looking into getting some nitro drop 2 shocks for the front, but I really don't think it will stop what ever is going on up there. The truck has been taken care of very well, this rattle or whatever it is will drive me crazy if I can't get it fixed. Can somebody please help!