I'm a new owner and was reading through the manuals when I came across information that stated 1800 rpm's to be ideal and it is best to select a gear to keep you close to this rpm. Following this guideline, 5th gear is about 1700rpm's and 70mph. Not sure when you would use 6th. Does anybody else do this? Or did I miss read?
That may be true if you were climbing significant grades. You wouldn't be going 70 mph in any case. Higher RPMs under load are going to increase cooling. 65 mph in 6th on your transmission will put the ISM11 at about 1400 rpm. That is pretty close to the performance/fuel economy sweet spot. If you are on reasonably flat terrain run in 6th gear at whatever speed you are comfortable with. I like to be under the speed limit enough to avoid the pass/re-pass game with trucks. Much less stress, better fuel economy.
I don't worry about it: the only thing I DO keep a eye on is the max rpm/ temps for our coach. With the great combos FT has with the Allison six-speed, no concerns: the Allison will figure it out! ^.^d The biggest problem I had when we got this coach, after two 'slow-pokes', was looking down and realizing, "I was doing 85." !
3126 Cat, 1700 rpm's is the sweet spot. Best mileage 8+, and happy speed for me. 62 MPH
" I am looking at the wold through a windshield, watching life fly by me on the right"......Commander Cody
I agree with Mike - for most normal flatland cruising conditions, just pick the speed where you are comfortable, and let the Allison brain box worry about selecting the gear. In almost all cases, it will make the correct choice.
I had to check ours a couple of times, so I was not ranked with a 'fish story': 3116 CAT.....12 mpg....75 mph/45 on 7% grades, it doth not care: what a sweet combo! b^.^d
Ifixboats...I completely agree with Roger....according to your signature your coach should have the M11 ISM450...the max torque RPM for this motor is 1450RPM. 4 stroke Diesels perform best at peak torque. 68MPH is where I hit 1450 RPM, and, for greatly increased fuel economy and longevity, I stay below that in level cruise as much as possible. Agreed, you'd never want to be in 5th gear intentionally in cruise, unless you just like buying diesel or your tranny has an issue. Select D and go, Allison 4000 will not up-shift to 6th until 60mph+. Use ECON mode for other than 60 slightly earlier up-shift points. Up long mountain passes, I will down-shift so as to keep the RPM at or a little above 1450RPM with accelerator barely off the floor...just keep an eye on coolant and tranny temps on long up-hill grades. Just my $.02. Woody.
You got that pointy nose helpin'....LOL
Amen on the 85! Found myself in that spot for a moment 2 weeks ago outside of Tucson. It can get away from you if you're not paying attention.....They sure ride nice! (Yes...I slowed down!)
Dave
It is good to have/know the torque curve for your engine. I like to go into a climb on the high side of peak torque so that as you slow down going up hill, you will drop down into the peak torque RPM which will help keep up your speed. If you start up hill at peak torque, you;ll start loosing speed and torque and steadily decline. Engines all vary in this regard, so know your torque curve and use it to your advantage. Have a great day ---- Fritz
My m11 not ism has gotten 8.2 mpg driving it hard when needed at 69 mph for the last 12k miles at 36,000 pounds combined.
Torque "feel" and horsepower revving it out are not a lot different.
But that's with a resonator not the oem muffler and easy rolling Michelin tires
Maximum engine life is not about treating your diesel with kid gloves. It's about managing engine temps while climbing grades and downshifting to allow the water pump to do it's job plus keeping the EGTs down. It's also about not idling your engine for extended periods, and cooling the oil temperature down before shutting down, especially at the top of grades where the oil will coke and ruin the turbo bearings and seals. Read the engine manufacturer's recommendation and you can't go wrong.
I beat both the U300 and MBZ 300SD hard but make sure the above is followed plus change the oil. The U300 has over 100,000 trouble free miles and the 300SD is approaching 450,000 miles without even a water pump replacement. Same for the transmission. When pulling a trailer, the 300SD is petal to metal for much of long distance trips. Still runs and starts like new even in sub-freezing temps.
Pierce