2021 Tacoma SR 4x4 utility model rear differential lock

It’s amazing that my aftermarket front locker hooks up with more ease than the factory rear did.

 

As others have said, your SR does not have a locking rear differential. If it did you would have a seprate button on the roof of your truck which would activate the rear locker. Your dealer gave you bad information.

After you've read the manual you may want to go find a dirt road or someplace unpaved to go 'play' with the 4wd system you do have so that you'll know how to use it when/if you actually need it. Plus (as it says in the manual ) you should be engaging the 4wd system (not on pavement) once a month or so for a few miles to keep everything working properly.

Good luck!