1. Verify that the joint shaft is not twisted or cracked.
2. Turn the joint shaft by hand and verify that the bearing rotates smoothly and freely.

Drive shaft
Joint shaft removal/installationMazda 6 Service Manual: Curtain air bag module removal/installation
Warning
Handling the air bag module improperly can accidentally deploy the air bag
module, which may seriously injure you. Read AIR BAG SYSTEM SERVICE WARNINGS
before handling the air bag module. (See SERVICE WARNINGS.)
1. Turn the ignition switch to LOCK position.
2. Disconnect the nega ...
Mazda 6 Service Manual: Dual proportioning valve inspection (without abs)
1. Connect the SSTs to the brake pipes as shown in the figure.
2. Bleed the air from the brake system.
3. Measure the fluid pressure of the master cylinder and the rear brake.
If not within the specification, replace the dual proportioning valve.
Fluid pressure
...