I have a 1997 F150 with the 5.4L engine and it has 230k on the odometer. Recently I’ve noticed from time to time, it will only rev to 4100rpm on the 1-2 shift with a noticable loss in power, and the 2-3 shift occures at only 3700rpm’s. This happens for maybe half of the time I’m driving during a 30 mile trip with quite a few stops. Sometimes the engine will feel strong again and it will rev up to the correct 4600+ rpm shift points, and then sometimes the power loss is evident and it will shift well short of it’s normal shift points. The transmission fluid is clean and full, the fuel filter was changed about 50k miles ago, and there is no CEL. I’m wondering if I have a fuel pump going bad or if it could be something else. What do you all think?
Check the vacuum to your transmission.
Sorry, kizwiki, but vacuum modulators haven’t been used since the early '90s on anything, and were largely gone by the late '80s. This truck has an electronically controlled transmission.
I’m a little curious as to your driving habits. Normally, to get a vehicle, especially a truck, to shift that late (4,600+ rpm) would require the accelerator to be floored, or close to it. Are you towing, or just like to drive hard? Does it feel like the transmission is slipping, and does it shift sloppy and/or harshly? Do you and others who ride with you consider your driving habits to be normal?