Will not shift into overdrive

2004 FORD EXPEDITION
220,000 MILES • 5.4L • V8 • 4WD • AUTOMATIC
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SLASHUGS
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Replaced alternator and it does not shift into overdrive. Could it be the amperage of the alternator? Checked the battery, fuses, etc., and they are all okay.
Nov 9, 2017 at 6:24 PM
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JACOBANDNICKOLAS
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Check for trouble codes related to the transmission. If it refuses to shift to overdrive, there should be a code to direct you to the problem. As far as the alternator, I would make sure that it is the same as came with the vehicle. However, unless it is really under powered, it should not cause this problem.
Nov 9, 2017 at 8:24 PM
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SLASHUGS
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The alternator that was put in came off a 4.6L. will that make a difference?
Nov 9, 2017 at 8:32 PM
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STEVE W.
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Nope.

Disconnecting the battery will reset the transmission controller and could make it not shift until the truck re-learns the shifting patterns. Normally on a Ford you can disconnect the battery, let it set for about twenty minutes to discharge the memory. Now start it and let it idle with everything off until it gets up to operating temperature. Now turn on the AC and drive it normally for five miles or so. Turn off the AC and see if it has regained overdrive.
Nov 10, 2017 at 5:13 AM
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SLASHUGS
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Thanks, I will try this and let you know.
Nov 10, 2017 at 10:59 AM