8 Speed Auto for HD trucks

Fish, haha!
Haven't heard that one in a while!

blt2ski wrote:

ib516 wrote:
Something to think about. A GM/Chevy 1500 with the 5.3L and a 6 speed auto is 2 mpg down across the board (city/hwy/combined) EPA ratings wise to the same truck with a 5.3L and the 8 speed auto and cylinder deactivation. So there's something to say for technology and more gears in the trans.

We posts see all the time in these forums when it comes to threads about the power wars in HD trucks:
"I have enough power, how about more mpg?"

Well, what if you could keep the same power and add 2 mpg across the board to your HD diesel?

There was a 3-5mpg gain in 2014 when going from the 4l60E to the 6l90E city freeway useage. Also a reason why I went with the 7 sp over a 6, 5 or 4 sp in my MDT. I was able to keep the engine in a 750 rpm power band, vs 1300 for the 4 sp auto, others in between. Not to mention overall low for those steeper grades etc was better!

Marty

There was a 1-2mpg increase with implementing DEF.

Grit dog wrote:

Me Again wrote:
So again, RAM/Cummins is working on a new setup that moves all smog treatment post engine. So it appears that mileage will be similar to a deleted truck right from the manufacture. And we all hear above the mileage deleted vehicle get. BIL 2008 RAM 2x4 gets over 25 MPG on the highway. 14 to 14.5 towing a 37' 5th wheel.

Money spent for this seems to return better bang for the buck than what more expensive 8 and 10 speed trannies will provide.

Let's not get too carried away here. MPG claims like this are kind of like peeing your pants in a dark colored suit. At first no one notices and you get a warm feeling. But pretty soon the smell takes over and someone sees the puddle by your shoe!

However I could be wrong. Don't know your BIL or where he lives, but he may only drive downhill at 52mph Max.

Don't piss in my boots and tell me its raining!

Grit dog wrote:

Me Again wrote:
So again, RAM/Cummins is working on a new setup that moves all smog treatment post engine. So it appears that mileage will be similar to a deleted truck right from the manufacture. And we all hear above the mileage deleted vehicle get. BIL 2008 RAM 2x4 gets over 25 MPG on the highway. 14 to 14.5 towing a 37' 5th wheel.

Money spent for this seems to return better bang for the buck than what more expensive 8 and 10 speed trannies will provide.

Let's not get too carried away here. MPG claims like this are kind of like peeing your pants in a dark colored suit. At first no one notices and you get a warm feeling. But pretty soon the smell takes over and someone sees the puddle by your shoe!

However I could be wrong. Don't know your BIL or where he lives, but he may only drive downhill at 52mph Max.

Actually they tow their trailer faster than I tow mine. They like 65ish and I like 60ish. We traveled together last fall from the NW to the Balloon Festival in NM. They always bought less fuel at each stop. So I think it is a fair comparison.

Me Again wrote:
So again, RAM/Cummins is working on a new setup that moves all smog treatment post engine. So it appears that mileage will be similar to a deleted truck right from the manufacture. And we all hear above the mileage deleted vehicle get. BIL 2008 RAM 2x4 gets over 25 MPG on the highway. 14 to 14.5 towing a 37' 5th wheel.

Money spent for this seems to return better bang for the buck than what more expensive 8 and 10 speed trannies will provide.

Let's not get too carried away here. MPG claims like this are kind of like peeing your pants in a dark colored suit. At first no one notices and you get a warm feeling. But pretty soon the smell takes over and someone sees the puddle by your shoe!

However I could be wrong. Don't know your BIL or where he lives, but he may only drive downhill at 52mph Max.

So again, RAM/Cummins is working on a new setup that moves all smog treatment post engine. So it appears that mileage will be similar to a deleted truck right from the manufacture. And we all hear above the mileage deleted vehicle get. BIL 2008 RAM 2x4 gets over 25 MPG on the highway. 14 to 14.5 towing a 37' 5th wheel.

Money spent for this seems to return better bang for the buck than what more expensive 8 and 10 speed trannies will provide.

ib516 wrote:
Something to think about. A GM/Chevy 1500 with the 5.3L and a 6 speed auto is 2 mpg down across the board (city/hwy/combined) EPA ratings wise to the same truck with a 5.3L and the 8 speed auto and cylinder deactivation. So there's something to say for technology and more gears in the trans.

We posts see all the time in these forums when it comes to threads about the power wars in HD trucks:
"I have enough power, how about more mpg?"

Well, what if you could keep the same power and add 2 mpg across the board to your HD diesel?

There was a 3-5mpg gain in 2014 when going from the 4l60E to the 6l90E city freeway useage. Also a reason why I went with the 7 sp over a 6, 5 or 4 sp in my MDT. I was able to keep the engine in a 750 rpm power band, vs 1300 for the 4 sp auto, others in between. Not to mention overall low for those steeper grades etc was better!

Marty

Something to think about. A GM/Chevy 1500 with the 5.3L and a 6 speed auto is 2 mpg down across the board (city/hwy/combined) EPA ratings wise to the same truck with a 5.3L and the 8 speed auto and cylinder deactivation. So there's something to say for technology and more gears in the trans.

We posts see all the time in these forums when it comes to threads about the power wars in HD trucks:
"I have enough power, how about more mpg?"

Well, what if you could keep the same power and add 2 mpg across the board to your HD diesel?

mowermech wrote:

valhalla360 wrote:

Me Again wrote:

So you are saying they are now throw away trucks? A Cummins engine can go a million miles. Wonder how many transmissions that will take?

The "million mile engine" myth...sure you can keep most any engine going that long but at 15k miles per year it will take 67yrs to hit 1 million miles.

Yes, most trucks are throw away before year 30 let alone 67. No manufacturer is designing and building based on million mile assumptions.

"million mile myth"?
it has already happened. I'm sure if you were to google it, you would find the reports.
My truck is almost halfway there, at 408,000 miles. The transmission was rebuilt once, and may need it again soon.
I got a good chuckle out of the "2 speed and three speed" comments. Am I the only one here that ever owned the GM Hydramatic 4 speed that Pontiac, Kaiser, and others used? Surely not. Even the military used it, or a variation of it, in 6X6 trucks. Of course, the M211 was quite possibly the sorriest 6X6 ever built...

Yup it's a myth....you're at 400k on a 20 year old truck. So get back to us in 30 years when it hits a million. Or tell you grandson to!
Why the chuckle? No I'd never heard of 4 speed hydramatics, but I just looked it up and realized they died almost 20 years before I was even an itch in my daddy's shorts!
And they were so awesome, I've seen exactly zero of them......ever. what again does it have to do with the conversation? They realized that less available gear ratios were better so they dumped it for half the gears and it took another 40 years for someone to realize that was a flawed theory?

Me Again wrote:

Bionic Man wrote:



Or, you could just leave it in Drive, and let the automatic move through the gears exactly as it was designed to do.

On down hills sometimes you what to manually select a gear in conjunction with the exhaust brake to descend a hill at the speed you want. As the truck does not know about curves or other conditions ahead of you.

Chris

I get the selecting a gear (or locking out) for downhill. In fact, I don't know why they don't put paddle shifters on the trucks for that.

But for regular driving, which is what I read the post I quoted as referring to, let the computer to its job.