Motor to Rear Ratio for Best M.P.G.

[BIGDOG]

Looking for any suggestions for MPG plus performance for following setup :
450 HP, Mercedes w/10SPD ultra shift, D-unit
What rear end ratio would be best for MPG and performance?

Thanks,
BigDog / Randy

 

[Dynamite 1]

bigdog, i have the big mercedes also @ 435, and a 6spd. allison auto. i would think w/the 10spd you could run 3:73 or 3:91 maybe even a 3:55. the object w/the mercedes is to gear it to cruise in all gears at around 11-1300 rpm. get your cruise speed picked [ what spd you want on highway ] mine is 69 and go from there. try to get this close and adjust it to what will be the best combo over all. this engine produces all hp/tqe @ 1100 rpm so it does not need to run fast. my trk has a 3:42 and turns 1325 @ 70 and gets a 9.3 mpg. on the low side and as high as 10.2 an this is w/idling added in. let it lug a little. if this is a new trk. the order process should suggest a rear ratio but have someone figure out all the choices. you could do the math yourself, it is a simple equation if you are not me. i am sure there is a site somewhere with the info. then do a comparison and pick what you want. mine has a 100,000 on it now and has run like a dream the whole time, only minor problems that warranty has covered. the solenoid for the engine brk. malf., sensors for blower motor an low coolant have both been replaced. and thats it, i guess i got a good one. keep us informed as to what you do . is this a trk you own or are thinking about buying?

 

[BIGDOG]

Dynamite - Thanks for the info, glad to hear good things. This is a truck we are purchasing. Also this is on a M2-112, have been assured by dealer (for what that's worth) that this is a Class 8 Truck. Any imput?

Thanks - Bigdog / Randy

 

[davekc]

112 is considered a class 8. It should have all class 8 warranties as well. If not, then it is a 7 with some 8 components. Match warranties with a Century or Columbia. They should be the same.


Davekc

 

[gojack]

Don't forget the wheel and tire size are as important as the rear-end ratio.

A good place to start is at http://www.powerspec.cummins.com
A nice on-line calculator, you can play with the different
parts to come up with your ideal spec.

Just use the rpm's/cruise speed you need for you and your engine.

Maximum MPG occures near max torque generation on torque curve.
11-1300 rpm On a MBE4000-450

Have you looked at a Freedomline Transmission?
would be better MPG than a Ultrashift.
(Freedomline skip-shifts automatically, Ultrashift runs em'all)


Good luck