Mine would not go at all into 2nd two weeks ago. Prior to shutting it down Tuesday night, everything worked fine. After starting it up Wednesday, absolutely NO 2nd gear available at all. No obvious indication prior to this such as excessive slipping or crunch or anything else.
transmission mechanic found a broken 2nd gear band strut. A $2 piece of metal. $120 labor and another $30 for oil, it was back on the road working fine.
Probably not what you are experiencing though.
Regards... ... . Hal