I've got an '87 F-250 w/the 6.9L and a c6 auto. Drove it this morning and everything was fine. went to come home this afternoon and shifted from 1st to 2nd fine but wouldn't shift up to 3rd to save its life! Any ideas what it may be?

 

C6 Diagnostic Tips | Ground Support Worldwide | Find Articles at BNET check this out and see if it will help

 

thanks. gonna try what they say and see if it works.

 

Mine did it when I lost vacuum at the brake booster

 

thanks. decided i'm gonna scrap the auto and just go w/ a manual!