You must pass the knowledge test:
You may take the knowledge test at any driver licensing office that offers testing.
Test scores are valid for 1 year from the date of the test.
After you’re issued a CDL, you may get additional endorsements or remove the air brake restrictions by taking additional knowledge and skills tests and paying all applicable fees.
Drivers who surrender their CDL or any endorsement will be required to pay all applicable fees, and may be required to retake knowledge and driving tests depending on the circumstances surrounding the surrender of the CDL or endorsement.
If you try to get a CDL fraudulently, your driver license may be cancelled and you may be required to wait for up to 1 year before you can reapply for a CDL.