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Pete, Auto Service Technician
Category: Ford
Satisfied Customers: 28246
Experience:  Over 17 years diagnosing and repairing automobiles various makes and models with some training and certifications.
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F250 7.3 diesel transmission fails to shift properly,

Customer Question

f250 7.3 diesel transmission fails to shift properly, disconnect battery and computer reboots it shifts perfect for sometimes months but lately have to do it more often. also if i turn on signal 4 ways it does same thing turn them off shifts right again is this a computer (pcm) proplem? this has been going on for about 200,000 miles. i have pulled very heavy traillers makes no difference.
Submitted: 1 year ago.
Category: Ford
Expert:  Pete replied 1 year ago.

Hi my name is ***** ***** I will be happy to help with this today.I apologize for any delay.

This can be caused by low voltage.If there is low voltage this will affect the electronics in the vehicle and can affect the transmission shifting like this here.I have seen loose and corroded battery cables cause this at the battery or to where they run and connect to as well as the electronic ignition switch itself sending low voltage.Turning on the 4 ways draws more power and is tied into the ignition switch which can cause low voltage to the transmission itself.

It is possible the transmission computer is the cause here as well.I have seen the computer act up internally causing intermittent faults.If you haven't had the fault codes read out/checked to see what codes are set this should be done.If any codes are set they will need diagnosed to locate and repair the fault here.This is best done using a scan tool that can plug in and communicate with all computers in your vehicle.

Low voltage or an internal computer fault is most likely at fault here.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service.You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.Thanks Pete.