Is the exh brake feature on the GM site yhe same as the downhill speed control on the Allison site?

How are they controlled?

thank you

I didn't go look at the sites, but I would bet no. An exhaust brake (most of the time) adds back pressure to the exhaust slowing the engine RPMs. The Allison braking slows by down shifting and using the RPMs.

Post links to what you’re looking at