· Old(s) Fart
The whole point of these girdle style covers is that you adjust the two preload bolts to minimize deflection in the bearing caps holding the carrier in place. The problem with this design is that aluminum only has about 1/3 the stiffness of the iron center section, so unless you crank on the bolts a lot, the aluminum cover deflects under load. It's not the best design, but it probably provides SOME additional support to the caps. The real problem is that people confuse "strength" with "stiffness".