Pulling an 9000# trailer on long Alaska trip. Since I’m hard of hearing my co-pilot, aka wife, hears a noise much like a freezer compressor comes on. I’m in tow mode and exhaust brake is on. Seems to never last long. Maybe a minute or so. Co-pilot says it doesn’t seem to matter if we’re going up or down hill. Maybe ruling out the downhill exhaust feature.
It’s freaking my co-pilot out so I’m asking the experts and those that hear better than I do if this is normal.
My older Duramax does something similar especially with warmer ambient temperatures. What mine does is cycle the engine's cooling fan clutch on and off, especially when towing, it only takes a minute or two in most cases to cool back down and then it goes quiet again. ~CA