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ScottG

Bothell Wa.

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Posted: 02/20/20 09:30pm Link  |  Quote  |  Print  |  Notify Moderator

Amazes me how quiet any of them are, even at full tilt.


Scott, Grace and Wesly
2003 Dodge 3500 4x4, 6 speed Cummins.
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4x4ord

Alberta

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Posted: 02/20/20 10:49pm Link  |  Quote  |  Print  |  Notify Moderator

Cummins12V98 wrote:

4x4ord wrote:

ib516 wrote:

I'd be surprised if the service brakes are activated without the pedal being pressed. Yes, I know radar (adaptive) cruise control systems do that and so can those pre-collision things, but that's different than a computer dragging the brakes down a grade. How do they know when to "let off" so they don't overheat? Temp sensors in the brakes now? I can't see that being the case.

I think the exhaust brake slowing the truck activates the brakes lights as they are programmed to do.



I am 100% certain that my Ford operates the truck brakes, trailer brakes, brake lights, exhaust brake and transmission shifting automatically when the auto exhaust brake is selected. It works extremely well.


NOT doubting you but why didn’t the Ford slow the load as well as the RAM?


The Ford applies the brakes to slow the truck to "the set point" which is the speed the truck was going at the time the brake pedal or accelerator was last released. after slowing the truck the brake is released and isn't reapplied until the truck accelerates beyond a certain programmed amount. (I don't remember how much it let the truck accelerate before applying the brakes again). Apparently the amount the computer was comfortable allowing the truck to accelerate was more than what Mr. Truck was comfortable with. The Cummins exhaust brake is either capable of holding an extreme amount of back pressure and so it is holding back without a brake application, as you say, or it is reapplying the brakes at more regular intervals to keep the speed more constant.

I think you've said that if you turn the exhaust brake on and let it hold back without utilizing cruise it doesn't hold back the way it does using cruise ..... I think that is the answer to whether cruise employs the wheel brakes or not ..... evidently it does. The other way you can find out is to go down your 14% grade on cruise with 25000 lbs in tow. When you get to the bottom let the truck coast to a stop, then get out and touch your brake rotors. I'd like to see a video showing the expression on your face the instant your finger touches those cold brakes.[emoticon]


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rhagfo

Portland, OR

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Posted: 02/20/20 11:18pm Link  |  Quote  |  Print  |  Notify Moderator

ScottG wrote:

Amazes me how quiet any of them are, even at full tilt.


Scott, we had a 2001 Ram 2500 CTD, and it was a bit loud, to say the least. DD has a 2004 Ram 3500 DRW CTD and it is noticeably quieter than the 2001.Now our 2016, is very quiet!! There are times I think it is a gas engine it is so quiet, then you hit a hill and while still quiet, it just climbs!


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Cummins12V98

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Posted: 02/21/20 08:17am Link  |  Quote  |  Print  |  Notify Moderator

ScottG wrote:

Amazes me how quiet any of them are, even at full tilt.


So true! My wife and I had to basically shout at each other in the 98 12V pulling the Siskyous, now it's just normal conversation.


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Cummins12V98

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Posted: 02/21/20 08:23am Link  |  Quote  |  Print  |  Notify Moderator

New RAM I honestly don't know what the brakes do but on my 2015 they do not come on.

I can't set mine to 35 and expect it to stay at 35 it simply is not going to happen with the trucks programming. I have to set it to say 30 and adjust up and down as needed depending on what the actual grade is to stay at 35.

jbc28

Gadsden, AL

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Posted: 02/21/20 08:26am Link  |  Quote  |  Print  |  Notify Moderator

4x4ord wrote:

Cummins12V98 wrote:

4x4ord wrote:

ib516 wrote:

I'd be surprised if the service brakes are activated without the pedal being pressed. Yes, I know radar (adaptive) cruise control systems do that and so can those pre-collision things, but that's different than a computer dragging the brakes down a grade. How do they know when to "let off" so they don't overheat? Temp sensors in the brakes now? I can't see that being the case.

I think the exhaust brake slowing the truck activates the brakes lights as they are programmed to do.



I am 100% certain that my Ford operates the truck brakes, trailer brakes, brake lights, exhaust brake and transmission shifting automatically when the auto exhaust brake is selected. It works extremely well.


NOT doubting you but why didn’t the Ford slow the load as well as the RAM?


The Ford applies the brakes to slow the truck to "the set point" which is the speed the truck was going at the time the brake pedal or accelerator was last released. after slowing the truck the brake is released and isn't reapplied until the truck accelerates beyond a certain programmed amount. (I don't remember how much it let the truck accelerate before applying the brakes again). Apparently the amount the computer was comfortable allowing the truck to accelerate was more than what Mr. Truck was comfortable with. The Cummins exhaust brake is either capable of holding an extreme amount of back pressure and so it is holding back without a brake application, as you say, or it is reapplying the brakes at more regular intervals to keep the speed more constant.

I think you've said that if you turn the exhaust brake on and let it hold back without utilizing cruise it doesn't hold back the way it does using cruise ..... I think that is the answer to whether cruise employs the wheel brakes or not ..... evidently it does. The other way you can find out is to go down your 14% grade on cruise with 25000 lbs in tow. When you get to the bottom let the truck coast to a stop, then get out and touch your brake rotors. I'd like to see a video showing the expression on your face the instant your finger touches those cold brakes.[emoticon]


When I am towing in the rolling hills around here with my F450 sometimes when I crest the hill the adaptive cruise will take it a couple of mph above the set point on the downhill. If the downhill is steep enough I can feel the exhaust brake kick in followed by the tap of the service brakes if it is steep enough. It is very evident at night with the reflection of the tail lights on the camper. Same thing on long steep downhills it will go 2 or 3 mph above then activate the brakes. This is a 2018 F450 with a combined 28-29k. I think Mr Truck wasn't comfortable going that far above the set point.


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4x4ord

Alberta

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Posted: 02/21/20 08:44am Link  |  Quote  |  Print  |  Notify Moderator

Cummins12V98 wrote:

New RAM I honestly don't know what the brakes do but on my 2015 they do not come on.

I can't set mine to 35 and expect it to stay at 35 it simply is not going to happen with the trucks programming. I have to set it to say 30 and adjust up and down as needed depending on what the actual grade is to stay at 35.



It sounds like the 2020 is like my Ford (uses wheel and trailer brakes as needed) where as yours is the older technology. The Cummins has an extremely capable exhaust brake. I find the exhaust brake on my Ford to be very impressive but based on how the Ram guys talk about theirs I believe the Cummins is even more impressive.

I am still wondering why your truck holds back more going down a steep grade using cruise than it does with only the exhaust brake switched on?

stsmark

Northern CA

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Posted: 02/21/20 08:54am Link  |  Quote  |  Print  |  Notify Moderator

So right at the 4:00 mark the info center in the gauge cluster is showing 230 hp of braking. That’s at 3500 rpm. Then it drops to 0 really fast. Cool that it has that page of info.

FishOnOne

The Great State of Texas

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Posted: 02/21/20 09:04am Link  |  Quote  |  Print  |  Notify Moderator

So to summarize:

Brake Applications:
Ram: 0 (Auto Brake assisted)
Ford: 5
GMC: 9

Time:
Ford: 10:20
Ram: 11:32
GMC: 11:47


'12 Ford Super Duty FX4 ELD CC 6.7 PSD 400HP 800ft/lbs
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ShinerBock

SATX

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Posted: 02/21/20 09:12am Link  |  Quote  |  Print  |  Notify Moderator

FishOnOne wrote:

So to summarize:

Brake Applications:
Ram: 0 (Auto Brake assisted-unproven theory by Ford fanboys)
Ford: 5
GMC: 9

Time:
Ford: 10:20
Ram: 11:32
GMC: 11:47

MPG:
Ram: 2.5 mpg
Ford: 2.4 mpg
GMC: 2.4 mpg



There, I fixed it for you.

I would still love to see how these trucks do at 80F or even 100F.

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