2018 Tahoe/How to control speed on mountain pass descents

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DPearson1

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We just upgraded our 2003 Chev Tahoe to a 2018 Chev Tahoe with the trailering package and 6 speed transmission. We pull a 22' travel trailer over Colorado mountain passes to our camping places. With the '03, we usually had to shift into low gear to make it up and to control the descent. With the '18, I am planning to use tow/haul mode while pulling the trailer up the pass. For the descents, I am planning to use tow/haul and Manual mode so that I can control the speed of descent by shifting to the best gear. I read one post that said tow/haul engaged powertrain grade braking. However, I read another that said engine braking was disabled while in manual mode. Is it true that engine braking is disabled in Manual mode? I'm very confused at this point. Can someone please help me? Thanks!
 

B-train

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I don't have a direct answer, but I do know that in tow/haul mode, it will allow the engine to close the throttle body for better engine braking. I've noticed on my 17 that it seems to take quite a bit for that to actually happen, and it requires the application of the brakes for a certain amount of time. And this was the same on my 2015 3500HD.

So, I just cover the brakes to engage the brake switch, not necessarily the pads. As the ECM sees that you have 'brakes' applied and aren't slowing down, it will fo from CAFE SUPER DUPER FUEL ECONOMY MODE, to an actual engine that closes the throttle body for a Jake brake like effect (and any older vehicle that doesn't drive by wire).

That being said, I've also had good luck with using manual mode and selecting the right gear. The rpms will be high, but it generally holds just fine. I've had to stab the brakes occasionally doing this method because rhe throttle body doesn't seem to fully close, making your speculation plausible.

Common sense goes a long way. Start slow on the downhill, and you'll be fine. The peeps that get into trouble are the ones who slow down too late, or ride their brakes for MILES and wonder what that smell is and why they ended up I'm the runaway ramp.
 

swathdiver

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...I read one post that said tow/haul engaged powertrain grade braking. However, I read another that said engine braking was disabled while in manual mode. Is it true that engine braking is disabled in Manual mode? I'm very confused at this point. Can someone please help me? Thanks!
It is true. If you are in range select mode the Cruise Grade Braking feature is turned off. Leave it in Drive and in Tow/Haul and it will work to maintain speed. If it doesn't, do it your way.
 
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DPearson1

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Thanks for you reply swathdiver. I'm concerned that I will be going much too fast on the downgrade if I leave it in Drive and Tow/Haul. With the '03 Tahoe in its low gear (3 speed auto trans), I was going 55 mph and had to do a lot of braking to keep the rpm's below 4000. I was hoping that I could use engine braking with the '18 Tahoe like I did with my old '93 Dodge and '71 International Travelall. Low gear on '03 was 3.06. Low gear on the '18 is listed at 4.027
 
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