GM and Ford’s stocks are higher as UAW strike kicks off. Their bonds tell a different story.

Ford Motor Co.’s and General Motors Co.’s stocks were higher Friday as workers kicked off a strike, but their bonds have been under selling pressure for some time.

Nearly 13,000 U.S. auto workers went on strike early Friday after the three automakers and the UAW failed to reach an agreement before their national contract expired just before midnight.

The…