Your engine has an engine brake and not an exhaust brake but regardless, as Lug Nut says, your toad brake is operated by air from your coach service brakes so engine braking has no effect. If you had a toad brake system operated from the brake light signal then the brakes would be applied.
John and Mary Knight
2015 Newmar Ventana 4311 - wheelchair accessible
2015 Cadillac SRX Luxury AWD