Laura & Charles
Well-known member
I’ve heard: Too much truck is almost enough.
2500
- Thread starter Fishspike
- Start date
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If you have answers, please help by responding to the unanswered posts.
rbrdriver
Well-known member
Yeah, go BIG or go home...........................
CharlesinGA
Well-known member
Actually not so. I too thought this till I got a diesel and did some reading. a gas engine has a throttle plate that restricts the airflow thru the engine greatly when closed (idle), so even though the gas engine does not have the compression of a diesel, it simply cannot pass the air thru, and thus "engine braking".
A diesel has much higher compression, so yes, higher initial resistance, but its canceled out by the engine not having any kind of throttle butterfly to restrict air flow. This is why exhaust brakes have been added to diesels, is to restrict the flow of air thru the motor. It works like the gas engine's throttle plate, but is on the outgoing end rather than the in going end like a gas motor. Then the diesel's braking becomes more efficient as it has the same air flow restriction, PLUS higher compression.
I have a diesel with no exhaust brake, and have to be careful on steep grades to slow down very slow, or nearly stop, and get in a gear at least as low as the gear I came up the grade in. (manual shift and it doesn't like downshifting while moving)
Charles
Scott 3
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I believe my Ram has a transmission sensor that detects the angle going downhill and will hold the gear I'm in or downshift. I can also manually shift to select or hold a lower gear. It works well but I imagine the diesel engine brake is much more effective. I try to be mindful of my brakes whether towing or not. I tend to get exceptional mileage on my brakes for all of my vehicles. Not tailgating makes a huge difference among other things. Do you ever notice other drivers pumping their brakes on open highways???
Never heard of a sensor that sensed angle in a transmissiom.
Dodge or Ram Cummins diesels since 2007 have a sliding plate incorporated in the turbo that whwn acrivated via swith and you let off the throttle effectively closes off the exhaust flow building back pressure slowing the vehicle. GM D/As use grade braking built into the Allison to somewhat achieve the same thing. Having owned both the GM works very well, but I like the Cummins setup better.
Dodge or Ram Cummins diesels since 2007 have a sliding plate incorporated in the turbo that whwn acrivated via swith and you let off the throttle effectively closes off the exhaust flow building back pressure slowing the vehicle. GM D/As use grade braking built into the Allison to somewhat achieve the same thing. Having owned both the GM works very well, but I like the Cummins setup better.
Skookum
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GM uses a variable vane turbo technology just the same. The fins on the turbo angle to create huge back-pressure when requested by the engine brake function. The Allison will grab a lower gear or two to assist in running the RPM high enough to create more pressure.
I prefer diesel and heavier duty platforms for towing heavy. I have an old LLY 6.6 Duramax in our motorhome. We towed across the country from Minnesota to Washington, Rockies, Cascades, and minor ranges in-between, and back!. At almost 30k gross combined motorhome plus pickup towed on a flatbed trailer, there just isn't a more comfortable, efficient way to do it than on a heavy duty chassis with a diesel.
Lou Schneider
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Not true. Compression is like a spring - the energy it takes to compress the air on the upstroke is returned on the piston's downstroke.
What provides engine braking on a gas engine is the throttle plate in the carburetor or fuel injection system that keeps the air to fuel ratio constant. When it's closed a gas engine has to work to suck air past it, creating the engine braking.
A diesel engine's air intake is wide open all the time. Not having to work sucking air past a partially closed throttle plate is part of what makes a diesel engine more efficient than a gas engine but the wide open air intake doesn't provide any engine braking. All you'll get is what's caused by the engine's internal friction.
To get decent engine braking from a diesel you need an exhaust brake, which is a throttle plate on the engine's exhaust which restricts airflow going out of the engine in the same way a gas engine's throttle plate restricts airflow going into the engine.
@Lou Schneider thanks for that info.... I'll get Steve to read it.
Rob&Deryl
Well-known member
Agreed. I have an exhaust brake but even so, I sometimes slip up and refer to it as the engine brake.
scottydl
Site Team
Also don't discount searching for a good used truck either. You can find one that is pre-DEF and pre-emissions (to some degree) and avoid those extra parts to maintain or eventually replace. That's what I did with my 2005 Silverado diesel dually that I purchased last year. Its towing capabilities won't match up to diesel trucks 15 years newer, but it will still outperform any gas chassis. We sold our travel trailer last month, but my plan is to hang onto the truck for an eventual fifth wheel purchase.
Tom
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An alternative to an exhaust brake on a diesel is an engine brake, sometimes known as a Jake Brake (or Jacobs Brake). When you step on the brake pedal, some combination of exhaust valves are opened near the top of the compression stroke, turning those cylinders into a power-absorbing compressor, providing the resistance for braking. (see manufacturer's explanation ).
Typically, a Jake brake has the option of two or three stages of braking, and is far more effective at braking than an exhaust brake. The resulting pop-pop-pop noise, especially on big rig tractors, has caused some communities to put up signs restricting the use of engine brakes.
An exhaust brake closes a flap in the exhaust system to provide some back pressure.
Typically, a Jake brake has the option of two or three stages of braking, and is far more effective at braking than an exhaust brake. The resulting pop-pop-pop noise, especially on big rig tractors, has caused some communities to put up signs restricting the use of engine brakes.
An exhaust brake closes a flap in the exhaust system to provide some back pressure.
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scottydl
Site Team
And older diesel trucks like mine (without engine or Jake braking) have a transmission braking option in “Tow Mode” that downshifts in ways to help slow the rig down. That is a feature on the Allison 1000 tranny that my Chevy truck has anyway. I’m not sure about diesel motorhomes of the same era.
CharlesinGA
Well-known member
Take that "list" with a grain of salt. The RAMS they mention, they are mixing generations with reference to the 1500's and problems in one gen were fixed in the next. Yes, there are problems, but nothing exceptional.Diesels cost more to buy but sell at a higher value than gas, 350s can carry more weight in the box than 250s and like the deisel have a higher resale value. FORD is the best selling truck in the world forcthe last 40 yrs for a reason. RAM has 3 trucks on the 10 trucks to avoid list
15 Used Pickup Trucks You Should Avoid – Autowise
autowise.com
Referring to the 2500/3500 RAM they cite death wobble quite prominently but fail to note that it only applies to 4wd models and generally only poorly maintained ones, usually with crazy oversized tires.
Just seeing that tells me the rest of the list is suspect also.
