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Discussion Starter · #21 ·
Drove towing 20,000 Lbs from Los Angeles to Sedona Az. 6% grades all kinds of road situations. Cruise control and no cruise control.
If the exhaust brake is working we can’t tell.
It worked superb on our 2015 in the same situations.
Very disappointing with the 2020.
 

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We pull loaded cattle trailers and an 8 horse trailer all the time. Put the trans in auto and tow/haul and turn the e brake on. Forget it after that- it takes care of everything. Your 10 speed won't work any different than a 6 spd other than your shifts are closer together. The cruise will help keep your speed down on downhills with the ebrake engaged and trans in auto T/H. Several owners on here use the manual selection for gears but the trans won't downshift in that mode- you have to do it yourself-something else to think about at a time when you can get real busy sometimes.
 

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Drove towing 20,000 Lbs from Los Angeles to Sedona Az. 6% grades all kinds of road situations. Cruise control and no cruise control.
If the exhaust brake is working we can’t tell.
It worked superb on our 2015 in the same situations.
Very disappointing with the 2020.
Thanks for posting this. If I test drive a 2020+ I will definitely pay special attention to that feature.

For your sake, you might consider making a service appointment at a dealership. If it's really not functioning at all there may be something wrong with the vehicle.
 

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That is one fine looking dually. We had a 17 Chevy dually same color as yours and man do i miss that truck! We like our 16 2500 short box but sure loved that dually for pulling. We always pulled in manual and went with 5th gear as the highest.
We had both the 16 & 17 at the same time and my bride always would question why i would drive the dually when the 16 2500 would do. Loved that dually and the size never bothered me for driving or parking.
Born and raised on a farm/ranch so did a lot of pulling through all my years back in NoDak. Retired and moved to AZ now so enjoy your younger years while they are here is all i can say!
 

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The tow/haul setting only affects the transmission shift points and the torque converter lockup. It does not affect the exhaust brake function.

According to GM the tow/haul function is designed to be most effective when the combined weight of the trailer and truck is at least 75 percent of the Gross Combined Weight Rating. With my truck that works out to a trailer load of more than 11,000 lbs.

If there is a problem with how the exhaust brake is functioning with the 2020 trucks I would look for a service bulletin as the controller programming may have a bug in it. There have been TSB's for the 8-speed transmission and torque converter clutch which may also be a factor.
 

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2021 GMC Denali 3500HD DRW
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For those that are not feeling an effective exhaust brake are you using cruise control? Mine can come on almost too strong sometimes.
Our 2018 would come on strong with cruise control, or when not in cruise, after a brake application--in fact it frequently held on too long. The 21 seems much more civilized but it will really pull you down when you need it. You just don't notice it as much as you did in the 18.
 

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So I just test drove a new 3500 Duramax Denali and came looking for information on the exhaust brake after my experience, or shall I say lack thereof. For reference, I currently own a 2016 2500 Dmax Denali and use the exhaust brake nearly every time I drive the truck. I live in Denver and use my truck wherever I go up to ski/snowboard, but also tow our camper in the mountains.
My experience from the test drive of the 3500 is that it CERTAINLY didn’t act like my exhaust brake compared to whenever I use mine (remember, I use it ALL the time in my 2500). Now, I clearly didn’t do a test drive with the exhaust brake using a trailer, as I don’t think a dealer would like that, but compared to when I drive my truck without a trailer and cruise and the exhaust brake, my truck will noticeably use the ex brake to slow down if the cruise speed is reduced - the 3500 appeared to do nothing when I reduced the cruise speed. I can confirm, though I don’t think there is question, that my truck works just fine with a trailer and the exhaust brake on cruise; it maintains my set speed within very close reason to the set speed even at 6-8% grades, like the IKE gauntlet grade from the TFL.
I can only surmise that the TFL test indicated the exhaust brake to do nothing because perhaps they took the cruise integration out, and now it only functions to help brake the truck when the brake pedal is applied; I can’t see it any other way. To be honest, if they truly took that feature out, I’m disappointed. I use it daily, and that missing will certainly make me consider just keeping my truck. That’s the main reason I bought the truck in the first place when I saw the original TFL test of the GMC exhaust brake on the Ike gauntlet and they didn’t touch the brake once (maybe he mentioned once), but they seemed highly impressed compared too the dodge and Ford that I didn’t even go look at them when buying my ‘16.
 

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With my 2011 LML the Grade Braking system is disabled if the transmission is in Range Select mode instead of Drive mode. The GM grade control works surprisingly well to control the engine and transmission in tandem on steep downgrades.

The exhaust brake is something I need to use far less with the GM grade braking in operation. But I suspect that most people use M_ and put the truck in a lower gear range and are not aware of the GM Grade Braking system that they have inadvertently disabled by doing so.
 
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I do recall noticing exhaust braking and cruise not working when I’ve put the gear selector into manual/Max gear, whatever GM actually calls it. As a result I don’t use what I’ll call manual much as the truck works great without it towing or not. I use cruise control and if I don’t like my speed going down a hill I reduce the speed using the cruise control system and it works great. If I come upon a reason I need to slow more quickly, we’ll that’s what the actual brakes are for and hey the exhaust brake kicks in on that too.

I think this is a little bit of diversion from the original topic though about people with what I’ll say is the previous generation of grade braking with the exhaust brake where it ACTUALLY functions seamlessly with cruise control, which it appears the new 2020s and2021 do not.

Please tell me/us, we are wrong, as this is one stumbling block towards me getting a newer truck than my 2016. The other is the fact that it doesn’t appear they included any options for built in rear seat entertainment to replace my in dash Blu-ray with OEM ceiling Mount display that also plays videos from SD cards - but that’s a whole nother gripe.
 

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I do recall noticing exhaust braking and cruise not working when I’ve put the gear selector into manual/Max gear, whatever GM actually calls it. As a result I don’t use what I’ll call manual much as the truck works great without it towing or not. I use cruise control and if I don’t like my speed going down a hill I reduce the speed using the cruise control system and it works great. If I come upon a reason I need to slow more quickly, we’ll that’s what the actual brakes are for and hey the exhaust brake kicks in on that too.

I think this is a little bit of diversion from the original topic though about people with what I’ll say is the previous generation of grade braking with the exhaust brake where it ACTUALLY functions seamlessly with cruise control, which it appears the new 2020s and2021 do not.

Please tell me/us, we are wrong, as this is one stumbling block towards me getting a newer truck than my 2016. The other is the fact that it doesn’t appear they included any options for built in rear seat entertainment to replace my in dash Blu-ray with OEM ceiling Mount display that also plays videos from SD cards - but that’s a whole nother gripe.
This observation is interesting to me. In my 2018 I do recall that on some descents when towing the exhaust brake was amazing and did a great job of holding my truck and trailer to desired speeds while on other descents it did not see the same benefits. I never did understand why the difference. I never thought to consider whether I was using the vehicle with the transmission in manual range.

Has anyone had a chance to test this idea in the vehicle with the new 10 speed?
 

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This observation is interesting to me. In my 2018 I do recall that on some descents when towing the exhaust brake was amazing and did a great job of holding my truck and trailer to desired speeds while on other descents it did not see the same benefits. I never did understand why the difference. I never thought to consider whether I was using the vehicle with the transmission in manual range.

Has anyone had a chance to test this idea in the vehicle with the new 10 speed?

My experience as stated above is that it didn't work at all while in cruise when I expected it to maintain speed on a descending grade - like mine does. I did, however, notice the exhaust brake appeared to kick in and work fine when actually braking using the brake pedal; that part acted the essentially same as my '16 - I could tell a difference, but it was a short drive. As I stated above, my sole experience since it was test driving the new truck, was that it didn't slow the truck on a grade, nor could I force the cruise control program slow the truck on a grade. I tried a it in trailer mode and normal mode.

I just used my '16 to haul my trailer and on flat ground on the highway in trailer mode, someone pulled in front of me, cruise engaged. I hit the speed down button and the truck downshifted the tranny, thus RPM went up, and the exhaust brake clearly slowed the truck down the ~5mph or so that I set it to pretty quickly without touching the brakes. I could not get the '21 to do any of that, flat ground, downhill, etc.
 

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2020 Silverado 3500 LT SRW Crew cab Duramax
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It's definitely different than the PacBrake I had on my old Dodge. I haven't tested it with cruise control to see if braking occurs while descending grades. However, simply tapping the brake causes a downshift and engagement of the EB. Coming down a 6 percent grade with switchbacks I would often slow the truck down for the tight turns using this method. Once you get the hang of it, it works great. I'm taking a trip this week where I hope to be able to test how it works with the cruise on.
 

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I'm pulling a 16,500 lb fifth wheel with my 3500 Sierra DRW. The exhaust brake in combination with transmission and cruise control works perfectly and keeps me within 1-3 mph of set speed on all terrain. Without cruise control (i.e. on twisty mountain hwys) I sometimes have to apply the brakes when I come up on a tight curve. The exhaust brake/transmission really jump in there and slow me down as they should but it can be overly aggressive when I get to the straight downhill runs where I'd like to coast a bit to get some momentum for the next uphill grade. It will not let go of the exhaust brake for quite a distance. I accelerate and it's still at 4000 rpm trying to slow me down. I turn off the exhaust brake at the switch--same result. It will eventually calm down but by then I've lost the opportunity. I had my 2018 act the same way so it must be normal behavior--but I'd sure like to be able to have it turn off when I want it to be off and not when the truck thinks it's ok.
 

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I'm pulling a 16,500 lb fifth wheel with my 3500 Sierra DRW. The exhaust brake in combination with transmission and cruise control works perfectly and keeps me within 1-3 mph of set speed on all terrain. Without cruise control (i.e. on twisty mountain hwys) I sometimes have to apply the brakes when I come up on a tight curve. The exhaust brake/transmission really jump in there and slow me down as they should but it can be overly aggressive when I get to the straight downhill runs where I'd like to coast a bit to get some momentum for the next uphill grade. It will not let go of the exhaust brake for quite a distance. I accelerate and it's still at 4000 rpm trying to slow me down. I turn off the exhaust brake at the switch--same result. It will eventually calm down but by then I've lost the opportunity. I had my 2018 act the same way so it must be normal behavior--but I'd sure like to be able to have it turn off when I want it to be off and not when the truck thinks it's ok.
Even on mine (2016), I’ve found that it gets hung up a bit. My solution that generally works is that you have to be accelerating under decent power and probably in level ground for it to give up the brake. I’ve found that you have to be intentional on the gas pedal, not just giving it a little “gas.” See if that works. Otherwise, yah I’ve had to disengage the brakes by hitting the button before too, but probably less than 5 times in my 33k miles, including a bunch of mountain towing.
 

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I’m curious if this is still an issue? I would think if it wasn’t working there would be a lot more complaints about it since these trucks are designed to haul heavy loads. Is it still the case where it’s working but might not be as pronounced as the previous gens?
 

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IDK what to say, I must be one of the only ones that has an operational exhaust brake. Mine works great. Barely touch the brakes towing my gooseneck loaded in the mountains. Been at 30,000 pounds and it still worked great, but haven’t had that much weight in the mountains yet. I have no complaints, seems to work better than previous generation Duramax’s.
 

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IDK what to say, I must be one of the only ones that has an operational exhaust brake. Mine works great. Barely touch the brakes towing my gooseneck loaded in the mountains. Been at 30,000 pounds and it still worked great, but haven’t had that much weight in the mountains yet. I have no complaints, seems to work better than previous generation Duramax’s.

BUT, do you use cruise, or do you just slam on the brakes and then see it work. Honestly, if it didn't work then, it'd be a total failure on GM's part. What I've commented on in responses above, is NOT that the brake doesn't work at all, its that it didn't appear to work with cruise control on like my truck does. As I said above, the thing that sold me on my truck 2016, bought new in 2016, was that I could be fully loaded (GCWR) going down steep grades on cruise and hold speed - which I can, not only with a trailer, but also without and fully unloaded just me inside; obviously, one needs to pay attention as far up as possible using cruise in this fashion, but the intention is to maintain speed, not run away. I drive a LOT in the mountains, and don't want to be riding my brake pads to keep speed in check, so I use the exhaust brake in my 2016 all the time, steep descents, flat ground, and it works NOT ONLY on braking maneuvers, but also to reduce speed when in cruise and I purposefully reduce speed. Have you, or can you try that out - using cruise with and without trailer? I have a feeling I know the answer, because a GM rep that went on a subsequent test drive with me, after returning on my own and asking the question, indicated that they reworked the software; I can't even get my father with a 2020 to confirm it works - though in his case I'm not entirely convinced he understands what I'm getting at, since he came from a 2005 of which they don't have exhaust brakes. Anyway...

Funny story, and in the end I was my own enemy, but my truck recently had a plugged DPF and GM roadside towed it to their nearest dealer (for partial story look up my previous posts). Anyway, as part of the "service," that ended up not being under warranty and I call BS on, the truck was set to service regen and the service advisor indicated the GM requires them to update the ECM software to the latest. We got the truck home after a 3 hour drive, 139 miles in the mountains, and it was essentially ready for another regen at 39 grams. Well, I already had a service date with my local dealer because of the same DPF issue when I called and set it up before it got to be debilitating on our camping trip. Since I was going in anyway I wanted to see if the truck would actually do the regen on its own. So I set out to drive, within minutes the regen started as expected; I bought an EDGE CTS3 to watch, and also not be stranded in the future. Anyway, at some point on the drive, while watching EGTs etc, I must have put the truck in manual range "M" mode (max gear) on the gear select, which I basically never do. So going down Floyd Hill on the way toward Idaho Springs from Denver on I-70 the truck kept accelerating, uncontrollably, down the 6%+ hill; I didn't realize it was in M mode, and was futzing with cruise, the exhaust brake, etc. I got toward the bottom and called my wife telling her that I was furious at the dealer for updating the software assuming it had something to do with the exhaust brake not working - thinking that they updated it to work like the 2021 that I drove. Fortunately, I found very shortly after the bottom of the hill my mistake of having it in M on the gear select. I'm happy to report the ECM update, assuming it actually happened, did NOT update anything operationally with the exhaust brake, as it worked great all the way back home down out of the mountains. Note that mention of it working in this last paragraph is in my 2016...
 

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Yes, I can confirm, exhaust brake will keep me at my set cruise speed while dropping down mountain grades while pulling a trailer. And as far as unloaded, it seems to keep me at speed also, but I don’t turn exhaust brake and T/H on when driving empty, seems kinda pointless.
 

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BUT, do you use cruise, or do you just slam on the brakes and then see it work. Honestly, if it didn't work then, it'd be a total failure on GM's part. What I've commented on in responses above, is NOT that the brake doesn't work at all, its that it didn't appear to work with cruise control on like my truck does. As I said above, the thing that sold me on my truck 2016, bought new in 2016, was that I could be fully loaded (GCWR) going down steep grades on cruise and hold speed - which I can, not only with a trailer, but also without and fully unloaded just me inside; obviously, one needs to pay attention as far up as possible using cruise in this fashion, but the intention is to maintain speed, not run away. I drive a LOT in the mountains, and don't want to be riding my brake pads to keep speed in check, so I use the exhaust brake in my 2016 all the time, steep descents, flat ground, and it works NOT ONLY on braking maneuvers, but also to reduce speed when in cruise and I purposefully reduce speed. Have you, or can you try that out - using cruise with and without trailer? I have a feeling I know the answer, because a GM rep that went on a subsequent test drive with me, after returning on my own and asking the question, indicated that they reworked the software; I can't even get my father with a 2020 to confirm it works - though in his case I'm not entirely convinced he understands what I'm getting at, since he came from a 2005 of which they don't have exhaust brakes. Anyway...

Funny story, and in the end I was my own enemy, but my truck recently had a plugged DPF and GM roadside towed it to their nearest dealer (for partial story look up my previous posts). Anyway, as part of the "service," that ended up not being under warranty and I call BS on, the truck was set to service regen and the service advisor indicated the GM requires them to update the ECM software to the latest. We got the truck home after a 3 hour drive, 139 miles in the mountains, and it was essentially ready for another regen at 39 grams. Well, I already had a service date with my local dealer because of the same DPF issue when I called and set it up before it got to be debilitating on our camping trip. Since I was going in anyway I wanted to see if the truck would actually do the regen on its own. So I set out to drive, within minutes the regen started as expected; I bought an EDGE CTS3 to watch, and also not be stranded in the future. Anyway, at some point on the drive, while watching EGTs etc, I must have put the truck in manual range "M" mode (max gear) on the gear select, which I basically never do. So going down Floyd Hill on the way toward Idaho Springs from Denver on I-70 the truck kept accelerating, uncontrollably, down the 6%+ hill; I didn't realize it was in M mode, and was futzing with cruise, the exhaust brake, etc. I got toward the bottom and called my wife telling her that I was furious at the dealer for updating the software assuming it had something to do with the exhaust brake not working - thinking that they updated it to work like the 2021 that I drove. Fortunately, I found very shortly after the bottom of the hill my mistake of having it in M on the gear select. I'm happy to report the ECM update, assuming it actually happened, did NOT update anything operationally with the exhaust brake, as it worked great all the way back home down out of the mountains. Note that mention of it working in this last paragraph is in my 2016...
Floyd hill to me is one of the best tests for the exhaust brake. In my 2015 I would tap the brake peddle with it on and it would downshift and hold that speed the entire time with my travel trailer behind me. I’m curious to see how my 22 will do once it’s finally here.
 

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I use my exhaust brake daily on my 2021 HD. Towing or not with and without cruise.

It’s my first diesel so nothing to compare it to.

It works well and holds speed perfectly on small declines ( TX is flat).

When approaching a red light I sometimes don’t even have to brake until I’m almost stopped.

Nearly all my driving is in the city so no comment on long hauls. That is in the near future.


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