The truck has to be increasing in speed with the brakes applied before the "exhaust brake" will work. Switching between tow haul will not automatically cause it to come on. Next time you are going down hill leave it in OD tow haul on and lightly press the brake pedal. The transmission should automatically downshift and the truck will start slowing down. You should not hear anything.
Haven't heard or read about the need to be increasing in speed with brakes on to get the exhaust brake to work.
I would rather it just come on in Tow Haul mode even if I am slowing without brakes applied in any gear.
I can be in Tow Haul mode on a steep downhill with load and braking or in the same gear braking without Tow Haul switched in and both feel the same resistance on the downhill.
I am used to my other truck exhaust brake being very noticable any gear and speed increasing not being required.
Has anybody else felt any exhaust brake difference switched in or out, not just the slowing by shifting down and brake application in Tow Haul?
I have switched the Tow Haul in and it has shifted down while braking as it should. Puzzling was I never could feel any difference in over 3000 miles towing 9000 lbs when I turned the Tow Haul off while remaining in the same lower gear with brakes being applied continuing down the hill.
I'll give it another go increasing speed from a downhill with brakes on in Tow Haul mode, then switching Tow Haul out and brakes still applied remaining in the same gear and see if its noticable. It should be as effective as other trucks exhaust brake.
If no noticable change in braking effect, I may need to head on over to the dealer.
So far I have gotten a few ancedotal responses of how it's supposed to work according to literature/manuals, etc., however only one response from another 2011 PS owner signature who also found no difference in Tow Haul mode in or out regarding exhaust braking.