CDL needed to be mechanic

That is a full in depth program.
I know the Mechanics at several company's I worked for just got trained by the company. They did not have to drive OTR or be prepaired too. So they tought them enough to pass the test, so they could proform the job they needed to do.
On the air brakes question, just look in any CDL study manual. It has all the air brake tests and everything else you need to know for your pre trip.
For a class B, you will need to take the general knowelege test and air brakes test. Then a driving test.

 

The tractor protection valve activates between 20 & 45 psig per Part 393.43:

http://www.fmcsa.dot.gov/rules-regu.../fmcsrruletext.aspx?chunkKey=090163348002391e

I would look into a six week course, I know there are programs out there that will get you familiar with the rules in less than 30 weeks. As a mechanic you will most likely be exposed to 100 air-mile radius rules.

Be safe.

 

I would think your company would supply the truck and a trainer to get your CDL. CDL schools teach their students to pass the test to get their CDL also but there you're paying for their equipment and instructors. They don't teach much more than that except for maybe logbooks and backing. If you do need to go to a CDL school I would recommend a community college because most of them are just as good and alot cheaper.