Autos vs Manual transmissions

So 1400 upshift than 900 rpm and rising under load. That's awesome for fuel economy but a good way to ruin engines by 500,000 miles. It's good for making liners dance around on all truck diesels. Does fuel economy pay for the rebuild costs? I'm no expert, I just talk to a few of them.

 

If the modern newbie was made to start in a old cabover or the likes with a manual. Id bet they would stop wearing shorts and flops in the winter.

 

Well, I guess Detroit is in the business of building engines and pairing them with transmissions that is guaranteed to reduce the lifetime of the engine 100% and they're such salesmen, that they can still convince carriers to buy doomed systems by the 100's of thousands and still warranty the engine and powertrain components to 500k miles



Carrier I work for runs them to near 450k-490k and trades them. They are good about performing the suggested preventative maintenance procedures and have relatively little problems [on an overall fleet scale] with the Freightliners and Detroit engine and auto transmission systems. And their retired trucks are highly valued by used truck dealers everywhere. So I don't know what to tell you. Keep living in the stone age if it makes you feel good.

 

Zeviander my '06 C13 shifts and pulls quite well @ 1400/1500 RPM and only rev to 1700/1800 if struggling up a hill . . . Am getting much better fuel mpg than the Paccar/Allison auto combinations if only for the simple reason don't race 4-wheelers OFF THE STOP LINE every time!!

Use 'Jake on' in local traffic practically 24/7 loaded is 'lower rpm pulling' rough on a CAT, causing unnecessary wear??

 

That's something a modern newbie would do....us old timers can think and adapt when necessary.

 

Besides. With an auto, you can hold your corn dog and leave the truck stop and hit the on ramp and always have a hand on the wheel.

In the first two weeks, I found myself wanting to clutch [and grab the stick] in critical situations only. I was not grabbing for a stick as bad as I thought I would. It was an easier transition than I thought it would be. All that said, If I were to buy my own new truck today as an owner-op, I'd buy a stick 13. But as a large fleet owner, I think the DT-12 auto and DD-15 engine pairing makes sense.

 

You're absolutely right.

These gear jammers that claim to know everything say they get good mileage by shifting at low RPMs. That just lugs the engine and puts tremendous strain on the engine components and will shorten engine life considerably.

RPM's don't kill an engine, lugging it does. And do that pulling 80,000lbs repeatedly year after year, and you wonder why you're blowing head gaskets and needing a rebuild at 550,000 miles.

With airplanes you have a gauge known as a manifold pressure gauge. It is used to ensure you're not overstressing the engine. Trucks don't have this so you really never know. But if you shift below 1300rpm you are lugging the engine. You may or may not get a tiny bit better mileage but blowing a gasket and needing a rebuild will more than cancel out any mileage increase you felt. You can tell if you're lugging the engine if you can feel it chugging along, without any real acceleration and with increased vibration. This is a sure sign of stressing the engine. Downshift a gear and get those RPM's up. Engines make power with RPM. They have a max torque RPM, keep it around there.

It's best to shift these trucks in their sweet spots, about 1400rpm. Mileage will increase by getting it into high gear (cruise speed) as quickly as possible as THAT is where the fuel savings is.

 

If it ramps up fast with autos like a few seconds a dont think that would be like the constant lugger hyper mile bonus type guys.

 

Another side note never long idle less than 900 rpm. It's according to all manufacturers for a reason.

 

That's actually true. Long idle at low rpm vibrates the engine. Weird, but true.

I think its more true for auto engines, not these big diesels that the manufacturers know will idle for extended times at truck stops.