You may be referring to the panhard rod that attaches to the axle and the upper right frame. It is a straight rod with an eyelet/bushing on each end about 1" or so in diameter. It is used to keep the axle in left / right alignment with the body. Without this bolt and panhard rod connected you could have serious handling issue while cornering as the axle can shift side to side without this rod in place. If this is the rod you are referring to then get the right diameter and grade bolt to go back in its place. I have never heard of a panhard rod bolt coming loose on its own. Unless it was loosened up for some previous mtce work and never retightened back to specs. If any doubts get the right bolt and nut from the stealer. Maybe someone else will jump in here with the correct bolt diameter and where you can pick one up without paying the stealers price for a bolt and nut. Hope this helps.

Ricochet