Driving 70+ mph today in 5th I went to downshift to 4th and it wouldn't go into 4th or 3rd. Slowed down and it will shift in 1st and 2nd but the shifter wouldn't go into any higher gears or reverse. This morning on startup I'd heard a high whining sound that went away after a couple of minutes at idle. The car shifted fine for about 15 minutes at speed, then without any noise or problems shifting, suddenly it wouldn't go into 4th or 3rd. I driove in 1st and 2nd home. I can shift as normal into 1st and 2nd. Later at home I find I can, with way more effort than normal, move the shifter into 3rd and 4th, but it refuses to shift into 5th or reverse. Clutch master fluid level is normal. Flushed out the system about a year ago. Any ideas what's going on?

 

Sounds like it needs a rebuild.