1. Inspect the dust boot on the drive shaft for cracks, damage, leaking grease, and looseness in the boot band.

2. Inspect the drive shaft for bends, cracks, and wear in the joint or splines.
Joint shaft disassembly/assembly
Drive shaft removal/installationMazda 6 Service Manual: Steering gear and linkage removal/installation
Caution
Performing the following procedures without first removing the ABS
wheel-speed sensor may possibly cause an open circuit in the harness if it
is pulled by mistake. Before performing the following procedures, remove the
ABS wheel-speed sensor (axle side) and fix it to an appropri ...
Mazda 6 Service Manual: Rear oil seal
REAR OIL SEAL REPLACEMENT
1. Remove the flywheel. (MTX) (See CLUTCH UNIT REMOVAL/INSTALLATION)
2. Remove the drive plate. (ATX) (See DRIVE PLATE REMOVAL/INSTALLATION)
3. Remove in the order indicated in the table.
4. Install in the reverse order of removal.
Rear Oil Seal Installation Note
...