[Richard]

Steve,

Those bolts are hidden. They attach the rear of the yoke to the transmission, and if you didn’t know how to look through a very small opening you won’t even know they are there. Look at the very first picture of the output shaft of the transmission. You will see three holes, the outer two are threaded. Those are the bolt holes for the offending bolts. If you do find the little window to look through, my bolts were socket head. There might have been a way to get a modified Allen wrench through the hole to tighten them but that is just a guess.

I took the rear assembly apart to gain unfettered access to the bolts.

The 8 bolts that hold the rear of the driveshaft to the transmission are not the ones that came loose.

The only way I know to check the integrity of the bolts that caused our problem would be to try and slide the driveshaft away from the transmission and confirm the rearmost piece of the driveshaft does not try to slip out of the tranny.