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Old 07-26-2019, 03:28 PM   #61
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They have mountains in Tennessee?
They’re hidden under the trees.
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At some point during every day you suddenly realize nothing else productive is going to happen the rest of that day. For me, it usually occurs around 9 am.
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Old 07-27-2019, 09:11 AM   #62
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Big difference

The tow/haul mode lets your computer know there is a potential heavy load and compensate accordingly and will usually lock out overdrive automatically. There is a big difference in downshifting and motor braking. Downshifting only causes the transmission to over-rev and overeheat. Our 2013 GMC 2500HD with 6.0 liter gas and 6 speed tranny uses motor braking. We live in the flatlands of Florida. The first time I tried it was traveling through Georgia. As long as the cruise control is set when you start down a large grade, the motor will activate its internal valves and sound like a semi on an offramp. It works great and reduces the need for braking.
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Old 07-27-2019, 09:14 AM   #63
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Originally Posted by tccommish View Post
There is a big difference in downshifting and motor braking. Downshifting only causes the transmission to over-rev and overeheat. Our 2013 GMC 2500HD with 6.0 liter gas and 6 speed tranny uses motor braking. We live in the flatlands of Florida. The first time I tried it was traveling through Georgia. As long as the cruise control is set when you start down a large grade, the motor will activate its internal valves and sound like a semi on an offramp. It works great and reduces the need for braking.
Im confused, are you saying you do not get any compression braking from your engine when you downshift?
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Old 07-27-2019, 09:16 AM   #64
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Originally Posted by tccommish View Post
There is a big difference in downshifting and motor braking. Downshifting only causes the transmission to over-rev and overeheat. Our 2013 GMC 2500HD with 6.0 liter gas and 6 speed tranny uses motor braking. We live in the flatlands of Florida. The first time I tried it was traveling through Georgia. As long as the cruise control is set when you start down a large grade, the motor will activate its internal valves and sound like a semi on an offramp. It works great and reduces the need for braking.





What 'Motor' do you have that can activate internal valves?
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Old 07-27-2019, 09:22 AM   #65
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There is some compression from taking your foot off the gas. There is no comparison to the increase of backpressure on a motor braking system.
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Old 07-27-2019, 09:33 AM   #66
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There seems to be some Heavy Duty guessing going on here. My '14 GMC 6-spd does NOT lock out overdrive with the Tow/Haul mode ON. Its two highest gears are OD and both are active with Tow/Haul ON.
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Old 07-27-2019, 10:22 AM   #67
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There seems to be some Heavy Duty guessing going on here. My '14 GMC 6-spd does NOT lock out overdrive with the Tow/Haul mode ON. It's two highest gears are OD and both are active with Tow/Haul ON.
Same thing with my 2018 Ford V10, 2017 Ram dually with CTD and previous ‘14 Ram 5.7 and ‘18 2500 CTD. They’re all a little slower to engage OD with tow/haul engaged but they all get there.
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At some point during every day you suddenly realize nothing else productive is going to happen the rest of that day. For me, it usually occurs around 9 am.
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Old 07-27-2019, 11:30 AM   #68
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Blackrock

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[/COLOR]


What 'Motor' do you have that can activate internal valves?
I will admit I was wrong. Eric H explained it pretty well.

Here is an explanation of the Jacob's brake that does incorporate a valve. No, my vehicle does not have a diesel.

What is an engine brake?
The Jacobs Engine Brake® (also known as the "Jake Brake®") is a diesel engine retarder that uses the engine to aid in slowing and controlling the vehicle. When activated, the engine brake alters the operation of the engine's exhaust valves so that the engine works as a power-absorbing air compressor. This provides a retarding, or slowing, action to the vehicle's drive wheels, enabling you to have improved vehicle control without using the service brakes*.
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Old 07-27-2019, 11:36 AM   #69
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I will admit I was wrong.

Sir, I commend you!! We have many wrong statements on this forum but very few will acknowledge being wrong. Peace!
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Old 07-27-2019, 12:20 PM   #70
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I have never done any Jake brake work on a Detroit engine but I have done a lot of Cummins, Mack and Caterpillar engine work. After emissions became an issue there was a lot of redesign work done with Cummins and Mack coming out with their own systems to work in conjunction with variable vane and waste gated turbos. These are all on their heavy truck engines.

All of the light truck diesels are using a type of exhaust brake in conjunction with some transmission retarding.


Gas engine trucks are using variable valve timing and transmission retarding by throtteling line pressures.
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Old 07-31-2019, 09:39 PM   #71
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Growing up in the mountains of Tennessee we used to shake our heads at the flatland tourists on the side of the road with their brakes on fire. I do worry about downshifting when she spins up to 3,500 rpm or more and brakes are cheaper than trannys but when the brakes overheat and fade out on a downhill you are out of options. Last week in North Carolina I saw my first tractor trailer at the far end of a pea gravel runaway ramp. Glad he was ahead of me.
Yikes
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Old 07-31-2019, 10:17 PM   #72
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My2014 Silverado 1500 has a vacuum pump driven by the engine to operate the power brake booster. Why? I suspect that when I let off the gas pedal, especially in 6th gear the computer cuts off fuel and opens the throttle blade for the fuel economy test. Perhaps in tow/haul mode the blade is closed when the transmission downshifts for more engine braking. It’s also possible that the torque converter is locked up when the engine braking is activated. I’ve never really tried that feature as I usually don’t engage tow/haul and just shift manually. Jay
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Old 07-31-2019, 11:24 PM   #73
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There seems to be some Heavy Duty guessing going on here. My '14 GMC 6-spd does NOT lock out overdrive with the Tow/Haul mode ON. Its two highest gears are OD and both are active with Tow/Haul ON.

While in T/H and cruise on, my 2018 F-150 has gotten into 10th gear. As I recall, I was in the flats of Ohio and had a tail wind....
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Old 08-01-2019, 10:39 AM   #74
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Just got back first trip with any hills (Tenn/north GA) pulling beast of 5th wheel (now sold) with my grocery getter .... in tow haul on my new 2019 Ram it worked great just a tap of the brake and engine down shifted slowed us nicely. I was surprised how well the 5.7 pulled up the hills not screaming but a strong low pull never exceeding 3300 rpms, pulled right past the semis then they would fly by down hill as I cruised at 63 ... New smaller shorter and lighter Rockwood will be here in 2-3 weeks I guess it is true when they say buy your 3rd RV first well this is #2 we hope to stop for awhile ...
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