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.
Output Shaft (Countershaft) Speed Sensor Replacement (A/T)
Remove the air cleaner assembly.
Disconnect the output shaft (countershaft) speed sensor connector, and
remove the output shaft (countershaft) speed sensor (A).
...
Parking Brake Inspection and Adjustment
Inspection
Pull the parking brake lever (A) with 196 N (20 kgf, 44.1 lbf)
of force to fully apply the parking brake. The parking brake lever should be
locked within the specif ...
Maximum Load Limit
The maximum load for your vehicle is 850 lbs (385 kg).
See Tire and Loading Information label attached to the driver’s doorjamb.
This figure includes the total
weight of all occupants, cargo, ...