ZDriver.com - 1985 non tubo tansmission or clutch problem?

Guys I really need some advice on an either clutch or transmission problem I had a few days ago. I was at highway speed on the interstate when I began hearing a loud high pitched squeal and then a high pitched vibration for about 30 to 40 seconds. At that point the car wasn’t getting power from the transmission and I began to coast. I was able to get the car to the shoulder and then tried to put the car back in gear but nothing was happening. With the clutch pushed in or out the transmission would go into 1st through 5th gears but nothing would happen. However when I tried to put the transmission into reverse it would squeal/grind either with the clutch in or out like before. I think this may be the clutch throw out bearing but I did not have any clues before that it was going out. The transmission and clutch were working perfectly up to this. This is the second transmission I have installed on this car but when the first one went it was nothing like this. Plus a few days before I had a jiffy lube check the transmission fluid level and it was good. The car is out of town and will be towed to a shop soon but thought I would ask around for opinions on what may have happened here first. Any related comments would be greatly appreciated.