I have a 94 z28 with the borg warner t-56 transmission.The problem im having is i cant down shift from 6th to 5th,but i can upshift from 4th to 5th.with the car stopped i can down shift from 6th to 5th.do i have a bad syncro or low transmission oil?

 

The problem started when i went to pass a car on the highway i went to down shift from 5th to 4th,but i accidently somehow managed to downshift into 2nd,which really bogged the engine down.Now i can downshift into any gears other than a 6th to 5th downshift.I have managed to shift to 6th at about 35 mph and then downshift to 5th,but i cannot down shift to 5th at highway speeds like i use to.anyone have any idea what the problem might be?