new to mixing.. too much low-end bass!

Trying to finalize my first recording project on Logic by doing the mixing on my own. I've got most of the mix sounding good, but whenever I burn out a cd to lisnten in car, the low frequency on the bass guitar is TOO LOUD and makes the inside of car rattle. Any suggestions on how to get the right mix? I have been at this all weekend and slowly loosing patience. Thanks!