The sealing rings are synthetic resin with chamfered ends. Check the condition of the sealing rings, and replace them only if they are worn, distorted, or damaged.
For a better fit, squeeze sealing rings together slightly before installing them.

Apply ATF to the new sealing rings, then install them on the secondary shaft.

After installing the sealing rings, verify the following:
The rings are fully seated in the groove.
The rings are not twisted.
The chamfered ends of the rings are properly joined.
Secondary HO2S Replacement
Special Tools Required
O2 Sensor Wrench Snap-on S6176 or equivalent, commercially available
Disconnect the secondary HO2S connector (A).
Raise the vehicle on a lift.
...
Maintenance
This section explains why it is important to keep your vehicle well maintained
and how to follow basic maintenance safety precautions.
This section also includes instructions on how to read the mai ...
Mainshaft Disassembly, Inspection, and Reassembly (A/T)
Inspect the thrust needle bearings and the needle bearings for galling
and rough movement.
Inspect the splines for excessive wear and damage.
Check the shaft bearing s ...