Re: Can someone identify this component?
B4 you remove that retarder look up Telma and other drive line retarders and see what they have to say. You can use that device anywhere you use your brakes, not just in the mountains. One thing to try b4 you go any further is to lube all your driveshaft U joints often and well, because vibration is one thing that will cause a retarder to become un balanced and malfunction. I would keep it on the bus if it were mine. It can extend your brake shoe life by 400 to 500%, saving you a lot of money on parts and labor.
You should have a on-off toggle switch with a small light nearby somewhere on you dash to turn it on and also have a small shift lever either in your steering column or around the dash that has 5 positions. The toggle switch sends power to the small shift lever in 4 of the 5 positions. You can see a demo on you tube.