Hey,
I was wondering how much torque is required to move CDL nut? I'm considering fitting a servomotor to move it, but have no clue at all if 1-2Nm would suffice or not.

 

I don't know the specific answer to your question, but I recall Disco Mike had some sort of electric motor setup to engage and disengage the CDL in his truck. I recall there being a couple others too. You could try searching for more information.

As for the specific torque, maybe you could crawl under your truck and test it.

 

As min01 said it's been done before.

Try doing a web search for something like...electric actuator CDL... maybe add Disco Mike and vehicle. You should find a couple success stories.
......

 

Ask and ye shall receive. Scroll to the bottom. There's a picture and a link to a website. Looks like the part isn't on the site any more, but you might be able to call the company or something. It uses a window motor.

2003CDLInstall - LAND ROVER CLUB V.I.