I have a 86 f150 4x4 (33x12.5) 136,000 miles. Lately i have developed a vibration in the front end on the right side when braking. I also have been feeling a thump like something hitting the bottom of the cab when turning at slow speed. this usually happens when backing out of parking spaces.I have been told that my radius arm bushings might need replacing. How can i determine if that is the true problem? And if it is the problem, how much should i expect to pay? If its not the problem, what could be other possible problems?