Well, not to belabor the point, but it looks pretty clearly to me like there is something loose inside the differential housing itself. As I said, i just put in new IRS bushings. Without taking out the driveshaft and playing around with the u-joint , i cant say for sure that its NOT the u-jjoint, but i cant see anything moving in the drive shaft/u-joint area, the tranny mount, or the engine mounts. If you put the car in nuetral, theres a lot of slop when i move the driveshaft, but it not the u=joint. The whole driveshaft moves, abouut a half turn as i said before, before it gets any resistance from the rear end. I may be wrong, but that doesn't seem normal to me. I've read a lot about Ford rear end slop on here , but I think this is a little more than just a little slop. Any ideas?