I ran over to AutoZone and picked up the u-joints that are supposed to be for my truck. They are too small. But in checking to make sure I had the right joint (and realizing the ones I got were too small) I also noticed that my u-joints, at least for the joint where the axle attaches to the yoke on the diff is not the same size in both directions. In the picture below, the top to bottom dimension is not the same (is smaller) than the side to side dimension.



In this second picture I'm holding up the u-joint I bought for comparison. It is a little difficult to see.



Is the larger u-joint (the one with 1.126" caps and 2 5/8 yoke diameter) built "square" (like the new one I'm holding) or "oblong" (like the one that's on the axle)? Do I have some kind of conversion u-joint currently installed or is this just how it is supposed to be.

Thanks in advance for the edumacation.