I have a 2017 33 DP Pace Arrow with the Cummins 6.7.

Does it have an exhaust brake or just a transmission retarder ?

Or maybe both ?

The Transmission down shifts when the retarder switch is on, but i dont feel the exhaust brake kicking in .

Jim Thomas wrote:

You technically have both, although the "exhaust" brake is actually a VGT or sliding turbo vane. It uses changes in the turbo geometry to create back pressure the way a traditional exhaust or Jake brake does. The Allison transmission controller also will downshift more aggressively to help slow things. 

One other note, when you have the engine brake switch on and it is activated (decelerating) it turns your brake lights on even if you aren't using the brakes. 

j

I have aa feeling the transmission is the only thing coming on ( down shifting when the switch is engaged) yes the brake lights do come on.