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Exhaust brake or lack there of... need others opinion on this?

firedab

By firedab
in 6.6L Duramax Diesel (L5P)

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firedab Enthusiast

firedab

Posted
Posted (edited)

So I have a 2020 Diesel with the exhaust brake which I believe is weak at best. I had a 2016 prior to this and test drove a 2017 before buying the 2016, and here is what I noticed. The 2020 has barely any exhaust brake compared to the prior years. When I'm towing 10k lbs or riding empty, my 2016 would downshift when the exhaust brake was turned on, sometime really aggressively reving up to 2500 RPM's or more depending on situation. When I test drove the 2017 which was obviously empty and not towing, with the switch turned on, I would tap the brake and it would almost come to a complete stop never having to touch the brakes until the very end. The 2020 with the switch on or off is almost the same, not downshifting and barely assisting in stopping, even with 10k lbs pushing it! I have not seen it downshift past 1500 RPM once on level ground. Now, in the mountains going downhill and either with or without the exhaust brake switch on, it would downshift and hold the speed, and even slow down. Is anyone else who pulls some weight noticing this? It would be most noticeable if you came from a 2016 or newer. I know the engine was updated in 2017, and now the 2020's have a newer transmission, but the brake assist is very weak IMO. I did take it in for service and had them look at it, which they said was operating normally and not showing any codes. Just a little disappointed...

Edited by firedab
EIKON Enthusiast

EIKON

Posted
Posted

That’s been a common complaint or observation on the 2020. The brake functions the same as the 17-19. But the transmission functions differently. Also keep in mind the previous years in the L5P would be a lot more noticeable due to the spread in the gear ratios. The 10 speed has to drop several gears in order for it to be as noticeable. 

 

I haven’t had any issue with it doing it’s job and I’ve towed loads at max gvwr. 

 

It just isn't as pronounced as previous generations. It’s main function is for downhill speed control and it does a very good job of that, for me. YMMV. 

  • 3 weeks later...
jkobs New Member

jkobs

Posted
Posted
On 3/11/2020 at 9:36 AM, firedab said:

So I have a 2020 Diesel with the exhaust brake which I believe is weak at best. I had a 2016 prior to this and test drove a 2017 before buying the 2016, and here is what I noticed. The 2020 has barely any exhaust brake compared to the prior years. When I'm towing 10k lbs or riding empty, my 2016 would downshift when the exhaust brake was turned on, sometime really aggressively reving up to 2500 RPM's or more depending on situation. When I test drove the 2017 which was obviously empty and not towing, with the switch turned on, I would tap the brake and it would almost come to a complete stop never having to touch the brakes until the very end. The 2020 with the switch on or off is almost the same, not downshifting and barely assisting in stopping, even with 10k lbs pushing it! I have not seen it downshift past 1500 RPM once on level ground. Now, in the mountains going downhill and either with or without the exhaust brake switch on, it would downshift and hold the speed, and even slow down. Is anyone else who pulls some weight noticing this? It would be most noticeable if you came from a 2016 or newer. I know the engine was updated in 2017, and now the 2020's have a newer transmission, but the brake assist is very weak IMO. I did take it in for service and had them look at it, which they said was operating normally and not showing any codes. Just a little disappointed...

Is your Tow/Haul mode on/enabled?  I've noticed the exhaust brake seems to be more pronounced when that is activated.

  • 5 months later...
JBalman New Member

JBalman

Posted
Posted

Yes I have noticed the same issue with the lack of exhaust braking.  Had a 2017 2500HD L5P and over a month ago traded for a 2020 3500HD drw. Love the new truck and the 10 speed Allison is amazing. But I miss the old exhaust brake function. This 20 just is not as effective.  GM: What happened?  Couldn’t the Allison be programmed to be more active with the downshifts to help increase the RPM?

Njmurvin Enthusiast

Njmurvin

Posted
Posted

I'll confirm that it seems to perform better with a load coming down a grade.  I tried it yesterday in town driving empty with T/H and EB on.  It made a slight difference but nothing compared to my old Dodge RAM with PacBrake. In that truck I didn't have to touch the brake until the PacBrake released at about 1100rpm.  That said, this new truck performed admirably coming down 6%+ grades and held pretty much any speed I wanted with 12k lbs in tow.

  • 3 weeks later...
Rguerra Enthusiast

Rguerra

Posted
Posted

I have noticed when towing down hill in Tow/Haul mode and EB engaged that if I press the brake briefly the transmission will downshift then if I repeat the Brake it will down shift again and hold my truck and load steady with noticeable EB sound.  Tapping the breaks to downshift seems different but it really works well in my truck.

redwngr Senior Enthusiast

redwngr

Posted
Posted
On 9/29/2020 at 2:30 PM, Rguerra said:

I have noticed when towing down hill in Tow/Haul mode and EB engaged that if I press the brake briefly the transmission will downshift then if I repeat the Brake it will down shift again and hold my truck and load steady with noticeable EB sound.  Tapping the breaks to downshift seems different but it really works well in my truck.

Tapping the brake the second time and the ecm figures you want more braking.

If ECM/exhaust brake can request the TCM perform a downshift if/when extra braking is required. 

(if the trans is in M mode, the computers won't do an automatic downshift)

 

Exhaust brake and transmission grade braking will also do their thing to prevent speed-up above a set cruise control speed.

farmingislife New Member

farmingislife

Posted
Posted (edited)

Former Ram owner here, traded in my '15 2500 for a new 2020 2500hd duramax.  The EB is working in the duramax, but it's barely audible, and it's only apparent after you've tapped the brakes.  It's definitely the not jet engine sound of the cummins EB, but it is there.  If I start heading down a hill and tap the brakes the EB will keep me at whatever speed I am at and will downshift to keep it there or lower.  Tap the brakes again and it will get even more aggressive slowing you down.  These are my observations so far riding around unloaded, I bet it is even more apparent once I get a load behind the truck.  I am happy with it, but there is some adjustment to the lack of noise and lack of immediate feedback when letting off the gas.  

Edited by farmingislife
  • 2 weeks later...
MrGraff Enthusiast

MrGraff

Posted
Posted

My experience with the 2020 diesel and exhaust brake is it works well.  The biggest difference I've seen is the transmission is much smoother and doesn't result in the jerk or sudden slow down that is perceived with the previous iterations.  Its also extremely sensitive to how hard the brake pedal is being pressed.  Did my yearly Colorado trip hauling 17000lbs this summer and if anything the exhaust brake worked better than previous generations.  

  • Like 1
  • 1 month later...
shadow gray 2020 hd Enthusiast

shadow gray 2020 hd

Posted
Posted

After pulling the stock trailer again, did notice a difference with the exhaust brake on versus pulling it with it off.  Could also hear it, but was not at all loud.  That is just a light load though, that trailer has no electric brakes on it.  Better test will come with a load of hay on the equipment trailer.  

JRSPerf. Enthusiast

JRSPerf.

Posted
Posted
On 3/11/2020 at 10:36 AM, firedab said:

So I have a 2020 Diesel with the exhaust brake which I believe is weak at best. I had a 2016 prior to this and test drove a 2017 before buying the 2016, and here is what I noticed. The 2020 has barely any exhaust brake compared to the prior years. When I'm towing 10k lbs or riding empty, my 2016 would downshift when the exhaust brake was turned on, sometime really aggressively reving up to 2500 RPM's or more depending on situation. When I test drove the 2017 which was obviously empty and not towing, with the switch turned on, I would tap the brake and it would almost come to a complete stop never having to touch the brakes until the very end. The 2020 with the switch on or off is almost the same, not downshifting and barely assisting in stopping, even with 10k lbs pushing it! I have not seen it downshift past 1500 RPM once on level ground. Now, in the mountains going downhill and either with or without the exhaust brake switch on, it would downshift and hold the speed, and even slow down. Is anyone else who pulls some weight noticing this? It would be most noticeable if you came from a 2016 or newer. I know the engine was updated in 2017, and now the 2020's have a newer transmission, but the brake assist is very weak IMO. I did take it in for service and had them look at it, which they said was operating normally and not showing any codes. Just a little disappointed...

Hello my Friend, what is your build date?

firedab Enthusiast

firedab

Posted
  • Author
Posted

Build date was 08/19, but have since traded in for a 3500, build date of 09/20 and they both behave the same.

Just came back from a trip in the mountains, pulling my trailer and I will agree grade braking works great, but on level ground, it is just not assisting. Its clearly the programming and if they would just reprogram it to downshift on level ground when in tow mode and EB on, it would make such a difference...  IMO

  • 3 months later...
Wyoming 3500 New Member

Wyoming 3500

Posted
Posted

First time diesel owner (2021 Duramax 3500) but have been traveling back and forth between NE Wyoming and Arizona frequently the past few months (already at 8k miles).   I can say that when running cruise with the EB off the truck doesn't hold it's speed at all on the downhill grades (set at 65 hitting 75 within a mile it seems), turning on the EB during those long downhills the speed stay's locked at whatever I put it with no variance.

Only towed the rig (14k 5th wheel) a short distance so far so I can't speak to it's effectiveness, but it does seem to work well in my opinion  traveling around Window Rock and Santa Fe.

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