Hey guys back again with another weird one. Since you were all so full of knowledge and help the first time I thought I would try again. Truck is 97 f super duty, 7.3L with auto transmission. Problem is eradicate shifting. No pattern at all. Scanned for codes because o/d light was flashing found nothing. Only thing I can repeat is it runs fine if you run it hard when warmed up. It's is not slipping and fluid is not burnt. All gears work but it seems to shift hard but don't slip. But vacuum pump on truck is non functional at this time. I am wondering if this Trans uses vaccum for any part of shifting or just electronics. Speedo works fine, Trans fluid temp is fine , truck is heavy but it was never like this before . Has 300,000 on truck and about 30,000 on trans. This seems to have started before but I recently installed led tail lights in it. I have heard this can cause a problem . But can't find a fix for it. Wiring is good and can shift Trans manually. Any help would be greatly appreciated.

 

I am also wondering which sensor the computer uses to shift the trans , TPS on engine or ACPS on fuel pedal ?