PM headed your way. Not gonna be much you can do through the drain plug

. Like pan said, get any possible clutch pressure off of it, and try to manipulate it. If that does nothing, drop the oil bag and take the ratchet top off. See if something is broken in there causing it to stay/pop into 4th.
If this is a new tranny, who is the manufacturer, and would it possibly be under warranty?
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