How do I engage "differential lock" on a 2000 freightliner century autoshift?

If it were me, I'd check the owners manual.

 

I have a 2000 century with a 10 speed autoshift. The transmission has nothing to do with the axle interlocks. On my truck I have four air control switches on the right side of the panel next to the airbrake locks (the yellow and red knobs). In order from top to bottom:

Suspension (for dropping the airbags)
Interaxle lock
Rear differential lock
5th wheel slider lock

I drove a Columbia about 6 years ago and as I remember it only had three locks on it. I think it only had the Interaxle lock and not the Rear differential lock.

Good luck finding an owners manual for a 9 year old truck. I have a couple of opt switches on my dash that I have never been able to find out what they do.

Ken

 

If it's not on the dash, the truck doesn't have it.