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Exhaust Brake and Towing - 2022 3.0L Diesel Sierra Limited

poppy510
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poppy510 Enthusiast

poppy510

Posted
Posted

I tow a small 4000 lb TT quite frequently, using tow mode of course. A few times, what I think is marketed as the exhaust brake, has activated. Typically it has been low speed (<20 mph) on a steep descent. Rather than an exhaust brake sound and action that i would expect, the truck downshifts to a lower gear and uses engine braking to slow the vehicle. The thing screams, like 3000-4000 rpm. I get no sense of low RPM Jake brake...just high RPM engine braking. I cant even get it to upshift by braking and going slower. Only getting on the gas will bring down the RPMs.  Is that it? I'm a little disappointed if so. What are you all experiencing?

 

redwngr Senior Enthusiast

redwngr

Posted
Posted

Does your truck have the Hill Descent feature?

Sounds like that's what you might be using. 

 

 

poppy510 Enthusiast

poppy510

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20 minutes ago, redwngr said:

Does your truck have the Hill Descent feature?

Sounds like that's what you might be using. 

 

 

It does, but I'm not using it. Just tow mode.

youcantkeepup! Enthusiast

youcantkeepup!

Posted
Posted (edited)

Its not a Jake break. Its an exhaust brake. It works by closing off the exhaust at the turbo. A jake brake works by dumping engine compression which is why they sound cool. Even the 2500's across the board do it the same way

Edited by youcantkeepup!
poppy510 Enthusiast

poppy510

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Interesting...I just learned something. Still, It sounds like an exhaust brake can provide somewhere between 60 to 80 percent of the rated engine power as braking power (compared to more than the rated power for a Jake Brake.)

 

All I am noticing is downshifting and high RPM "engine braking." It certainly does not feel like a couple hundred horsepower worth of increased backpressure in the exhaust manifold causing the vehicle to slow down.

 

Maybe the exhaust brake on the GMC is coupled with automatic downshifting when necessary, and at low speeds the downshifting happens since not a lot of exhaust backpressure is available. It's possible that at high speeds while towing my exhaust brake has been working perfectly and I just have not notice it because it is quiet, and enough backpressure is available to not require automatic downshifting.

 

Cheers

poppy510 Enthusiast

poppy510

Posted
  • Author
Posted

Just confirmed. Exhaust brake is coupled with downshifting when necessary. The downshifting is just more noticeable at low speeds and steep grades.

 

 

 

"The diesel exhaust brake available on 2020 Silverado and Sierra light-duty and HD models equipped with the 3.0L Duramax diesel engine (RPO LM2) or 6.6L Duramax diesel engine (RPO L5P) enhances the vehicle brake system by using engine braking and automatically downshifting the transmission to help slow the vehicle.

 

When the diesel exhaust brake is active, transmission downshifts may be automatically selected to increase engine speed, which increases the effectiveness of the exhaust brake. The number of downshifts selected is determined by the length of time the brakes are applied and the rate the vehicle is slowing. The system will not downshift the transmission if the vehicle is in Range Selection Mode.The diesel exhaust brake function on the 3.0L diesel engine is part of the Tow/Haul Mode Grade Braking system. Tow/Haul Mode Grade Braking is only enabled while the Tow/Haul Mode is selected."

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