Hey guys, got a question here. Got my motor running after replacing the rockers, and rods. When taking it for a drive I noticed that it won't down shift. It's like she's stuck in first gear. I can shift into reverse, drive, everything and you can feel her slam into gear. Transfer case shifts and works fine. Could this be the result of a bad vacuum line causing the automatic trans sensor not telling it to downshift? No check engine light has come one either...yet.

89 F-250, 351w, C-6 auto, no o/d, 4x4