Was the transmission new or rebuilt?
Any time there is shifting issues first thing needs to be checked is the transmission fluid.
Make sure it is at the correct level also the fluid is in good condition. Since the transmission was replaced, the fluid condition should be good.
However, if for some reason you have a hose that starts to leak, that can make the fluid go low.
If this was a rebuilt transmission, it is possible to have an issue with a internal component failure. You could have faulty pressure switch or shift solenoid.
Sometimes when there is transmission issue the check engine light gets illuminated. Is your check engine light on? If so, scanning for the code(s) can help with the diagnostic process.
Please let me know of any questions.
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Thursday, October 7th, 2021 AT 8:35 PM