Companion Flange

WARNING: This page is about a different car, the 2013 Subaru Forester. However, it is still accessible from the selected car via links, so may be relevant.

If rust or dirt is attached to the companion flange, remove them.
Set a dial gauge at a companion flange surface (mating surface of propeller shaft and companion flange), and then measure the companion flange runout.
Limit of runout:

0.08 mm (0.003 in)

Fig 1: Measuring Companion Flange Surface Runout
Courtesy of SUBARU OF AMERICA, INC.
Set the gauge inside of the companion flange, and measure the runout.
Limit of runout:

0.08 mm (0.003 in)

Fig 2: Measuring Inside Companion Flange Runout
Courtesy of SUBARU OF AMERICA, INC.
If either runout exceeds the limit, move the phase of companion flange and drive pinion 90° each, and find the point where the runout is within the limit.
If the runout exceeds the limit after changing the phase, replace the companion flange and recheck the runout.
If the runout exceeds the limit after replacing the companion flange, the drive pinion may be assembled incorrectly or bearing is faulty.