I was taking my 79 z28 out for the first real drive of the year after a ton of work this winter and on the way to point A the car drove amazing tested up to 75 miles an hour with 0 hard take offs and on the way back the car was fine and about a mile into it the rear end wobbled for a split second and then the cannon sound from the right rear of the car went off and the car rumbled to a stop on the side of the road i looked underneath and the drive shaft was still intact but i didnt shake it or look to hard because didnt have the space on the highway i tried to limp it back to the place i had just left to take a look at it and as i went to put it in reverse to turn around the driveshaft fell out i pulled it out of the trans on the spot and the u joint looks good the flanges were still on the yoke and tight but it had came off the rear end the caps and needle bearings are gone but my question is how can the u joint come out with the flanges still hooked up??? do you think the whole rear end is bad the center bolt is still tight on the rear yoke as well?? when i towed it home with a truck the car didnt shake at 10 miles an hour and i put it up on jack stands to see if i could hear any noise but nothing sounds fine nice and quiet where should i start by the way its a stock rear end and havent done anything to the rear of the car yet

 

This is where a picture would be helpful. Could be that the rear u-joint blew up, or it wasn't bolted tightly to the rear yoke and the caps flew off. With the caps gone, the u-joint can come free of the yoke, even with the clamps & bolts still in place.

 

sorry about not having the pics the u joint did go bad but the main cause was the drive shaft was out of balance and the knuckle was bent on the shaft they straightened and balanced it new u joint and all it cost was 150 so not too bad considering what i was prepared to tell my wife how much a new rear end would cost lol

 

I guess my question is how did you get to 75 with everything feeling "amazing" and not feel any vibration? One would think a driveline far enough out to explode a U joint would really vibrate at some point betwen 0-75mph?