I get a thump under my drivers side seat when going over bumps. I checked everything for play/slop: sway bar, transmission mount, exhaust, ect, everything was O.K there. I noticed the transfer case has about 1/2" of vertical movement and there's about the same amount of space between the skid plate/crossmember. Should the bushing under the transfer case fill the whole space between the case and the crossmember? Or should I look somewhere else?