Automatic vs Manual

That's how is designed to operate on the Detroit. Anytime you turn on stage 3 engine brakes. The computers will always keep the egine RPM 1750-2200. What is does to give you maximum braking power it just keeps down shifting gears for you. So you can go from 65 MPH all the way to 15 MPH with maximum engine brake if you need it. Once it drops to 1750 RPMs it drops to next lower gear and keep slowing you down till you turn it off. It a nice setup

 

You did notice my earlier post where I said that sometimes you can not let the system control things?

It is not just the transmission, it is the combination of engine/transmission/computer, and when that does not slow you down enough you go to manual.

Again, get real.
It is a very good combination of engine/transmission/computer, but the driver still has the final control of how things work.

And the gearing in the transmission DOES have an effect with the braking force when working with the engine brake.

 

I'm not trying to make up time going downhill. Many do.
My point was that the speed is better controlled with this combo, and so I can maintain a better speed going downhill.

Why are you SO confrontational about this?

And it was one of the Detroit engineers that explained to me how these engines and transmissions were designed.
Running the engine up to 2200 accelerating would likely cause damage, but downhill on the engine brake is fine. They designed it for that.
So get into the real world.

 

Good info on here for people considering buying 3 year old fleet trucks.... proof they have the hell pounded out of them.

We will have to agree to disagree I guess. I'd like for someone who actually owns a similar truck that you drive come in and say they run it way up in the rpm range. It must be a poor design if you don't get sufficient engine braking holdback without going up that high.

 

I'm bored and I think I'm right and you're wrong.

 

You are getting bored, likely, because you have no correct answers to throw back.

 

Lol
Okay.

 

I tend to run that engine brake somewhere near high horse. What I do is drop enough gears until that jake causes the rig to nose down too much and fall off it's tach. Then the next gear up should be where that jake will hold it all the way down with a margin of safety with cold brakes.

I might be the slowest coming down but I will get down regardless of grade. There have been times Ive gotten down really fast pretty much where gravity will quit pulling at god knows how fast before the bottom. I would love to turn in a truck that did 140 plus maybe 150 recorded on the computer for the suit to revel in...

There have been plenty of old iron with jakes running 2300 minimum. If the engine is really smooth, we would let her come up to 3 grand.

I cannot imagine abusing a engine like that these days, It must have taken decades off it's life span.

 

Any engine will give more braking power the higher the RPMs. So Detroit just taking advantage of that. Stage 1 and 2 keeps the RPMs 1200-1750. When you want lots or braking power go to 3. I go as fast as other drivers, and I can smell their brakes. I don't even touch my brakes going downhill the same hill. So it not like we are go crazy fast. Just taking advantage of the technology.

 

I know... right?

I was blown away when this Detroit guy was telling me about the new DD15/DT12 combo.

But then, my first 'smart phone' was acquired in the last six months. I hate 'progress'.
I only got it because when I have my daughters in the truck they tend to spill drinks on my phone, and break them. This one is waterproof, and shockproof.

Only time will tell if this engine/transmission combo will work out well. But so far I have been impressed by it.