How can I lose 5th and 6th gears in my t56?

This morning I was leaving work, when I put my trans in 5th about 50mph it was like neutral, same with 6th. Everything else works but no 5th or 6th. What could have happened?
Its a 95 Z28 with 230,000 miles.
Thanks.
Ron

Ron,

There are several problems it could be but none of them would be good. I would recommend not driving it until it is checked out. You could have broken the slider, gears or who knows what else. The car has quite a bit of miles on it so anything is possible.

Joe

Thanks Joe, I drove it home 40 miles and it was nice and quiet but just no 5th or 6th. I'm going to leave it sit until I figure out how I'm going to it fixed.
Ron