Cummins M11 gearing

[lhwood]

Greetings,  I have a bit of a project here.  I'm putting a M11-450/Allison 4060 in a 102-C3 and am trying to decide what rear end gearing to go with.  What should my 70mph cruise rpm be for fuel economy?  The bus/toad combined weight is around 47K.   I'm thinking around 1500rpm.  Anyone else here using the M11 or have previous experience?

Thanks in advance!

[luvrbus]

Greetings,  I have a bit of a project here.  I'm putting a M11-450/Allison 4060 in a 102-C3 and am trying to decide what rear end gearing to go with.  What should my 70mph cruise rpm be for fuel economy?  The bus/toad combined weight is around 47K.   I'm thinking around 1500rpm.  Anyone else here using the M11 or have previous experience?
You are going be in 4:36 to 4:56 range,did you buy a package deal the 4060 is a PTO transmission   

Thanks in advance!

Greetings,  I have a bit of a project here.  I'm putting a M11-450/Allison 4060 in a 102-C3 and am trying to decide what rear end gearing to go with.  What should my 70mph cruise rpm be for fuel economy?  The bus/toad combined weight is around 47K.   I'm thinking around 1500rpm.  Anyone else here using the M11 or have previous experience?

Thanks in advance!

[lhwood]

Luvrbus, I did buy the engine and tranny together.  It was a zero miles engine from an rv so this just a 4060 not a 4060P--no pto on this one.  Long story but it was an unfinished project motor home that had an engine replacement that was never completed.

[lhwood]

My gearing options: (bus currently had 3:21's)

4:10 and have 1475 rpm @ 70
4:30 and have 1550 rpm @ 70
4:56 and have 1644 rpm @ 70

The 4:56's are pretty easy to find since that seems to be the ratio for series 60 transit buses.  The 4:30 is common for the charter buses.

[RJ]

My gearing options:

lhwood -

What rpm is the torque peak for the M11?

Below the torque peak you're lugging the engine, thus wasting fuel.

From the torque peak until it starts to drop off is going to bring the best performance.

Regardless, pushing a 47K vehicle with the aerodynamics of a brick thru the air at 70 mph is going to yield somewhere between 5-8 mpg, depending on terrain, genset usage, traffic, and a whole lot of other factors.

People tend to forget that wind resistance goes up by the cube of the speed - it's not linear, it's parabolic.

FWIW & HTH. . . 

RJ

[Tom Y]

I put in an L10 w/740, wanted faster gears went to a 3.38 and 24.5 tires. Came across a new world with the 2008 rv crash. Wish I had my 4.10s back. So I am now just running 5 speeds.

A gear change would be good for you, and me also. Just not wanting to go through the programing and buying/switching gears.  Good luck 

[luvrbus]

M-11 Cummins are all over the charts with hp,torque and rpm settings all depends on how it was ordered,my sons M-11 Plus 450 hp with the 4060P is a 1800 rpm  engine with 4:30 gears it does ok,I get better fuel milage with my ISX 15 Cummins pushing a larger and heavier coach that he does with the M-11

[chessie4905]

Find out what trucking companies are using for their top gear ratio, and cruising rom. Fuel economy is paramount for them.

[luvrbus]

Find out what trucking companies are using for their top gear ratio, and cruising rom. Fuel economy is paramount for them.

Allision has a application manual if you can get hands on one, that tells you the gear ratio ,for cooling,torque ranges in each gear and for the best rpm for lubrication for the transmission, the 4060 and all generation 5 WT are not as touchy as the early B500  generation 1 and 2 were,the later generations of Allision control the engines they tell the engine what it wants and needs

[lhwood]

lhwood -

What rpm is the torque peak for the M11?

Below the torque peak you're lugging the engine, thus wasting fuel.

From the torque peak until it starts to drop off is going to bring the best performance.

Regardless, pushing a 47K vehicle with the aerodynamics of a brick thru the air at 70 mph is going to yield somewhere between 5-8 mpg, depending on terrain, genset usage, traffic, and a whole lot of other factors.

People tend to forget that wind resistance goes up by the cube of the speed - it's not linear, it's parabolic.

FWIW & HTH. . . 

RJ

It seems torque is rated at 1,200  rpm.

[luvrbus]

They could be anywhere on the chart you need run the serial numbers by Cummins to find out for sure it being a new engine ,they can be anywhere from 1200 rpm to 1500 rpm for the torque curve.If you don't have the cradle Sam Caylor probably has one for the Cummins,and if it doesn't have the bus oil pan those are pricey new ($1200.00)