ok so 1991 f250 7.3L e40d tranny. i had it rebuilt about 3 months ago and still shifts bad the spedo dont work unless im flooring it from a stand still even then it only says im going slower then 10 mph. i checked the cable to the spedo and to the rear of the trans case it looks good. put in a drill and spun it it regestered at 75 mph so i think the cable is good. i checked the vss sensor at the rear axle and looks good and is brand new from the shop. need help guys im going crazy.... maybe the guage cluster is going bonkers bad ground but idk where it grounds out to . please i need help im pulling my hair out. thanks tim

 

The bad shifts are probably a result of a bad torque converter. Clean all the grounds, never can hurt. My speedometer reads about 10-15 mph off as well.