stupid question,but have you (1) checked the idler arm bushes on the left hand chassis rail,these wear because of lack of lubrication,& can have this effect,or (2) you haven't dropped a bolt out of a caster rod,this little darling happened to me once,& the car bump steered violently under brakes.just somethimg else to check before all the heating,hammering & swearing you seem to be headed for.definitely using the bashing smiley with this one