2013 Pinnacle gear train

[LSI]

I am on a somewhat dedicated run.Central Illinois to SC via Atlanta.Cruise speed is 62 mph.I'm looking at the M drive.Should I go with the Direct or O.D.?With the hills I'm looking at the direct drive.If so which rear end ratio should I go with?I'm going with the 505 hp.My other run is on 2 lane road 55mph from Peoria Il to Toledo OH to Canton MI back to Peoria Il.

[larry5332]

I have a 2011 with 3.21 rears, overdrive mdrive,run 60 mph from Texas panhandle to southeast. Have only had this truck for couple weeks, am very happy with it so far. I say overdrive. If you don't run any " major" mountain country I would say gear it out close to mine with overdrive. 62 mph would be 1300 rpm's. I'm seeing high 6's with mine right now, loaded close to gross both ways pullin refer.

[rsb502]

505hp MP8, with an 18 spd, or M drive 12 spdO.D. trans and 3.86 rears with lo pro 24.5's would be my drivetrain of choice, plenty of gear for torque in hills and a good cruise rpm and always go with O.D. its just not worth it to go with direct anymore you can always drop a gear and keep the rpm and road speed where you want it. I dont know what kind of gross weight you are hauling but if you are light or never plan to get into big hills 3.36 rears would also be a good choice, 3.21 would never work here in the southeast US too many hills and I always ran close to gross you would lug then have to drop two gears to keep the rpm in the right range, However if you plan to run low pro 22.5 tires go 3.36 or 3.21 rears the road speed/rpm matches up with 3.36 and low pro 22 to 3.86 and low pro 24. Just my two cents worth

[bts-4120]

I don't think the od in the m drive is as tall as a fuller and deff. not as tall as a Mack one reason why you see alot of them with 3 21 gears

[rsb502]

Mack wants the MP engine series cruise rpm to be in the 1350 to 1450 rpm range to get the best fuel economy so the higher gears are spec to get that rpm range at 70mph, thats the key find out what you think your average cruise speed will be and tailor the gear ratio accordingly for the tire height you are running to get the rpm where the engine is at its most efficient. I like 24.5 rubber so 3.21 wont work as well for me it works great for low pro 22.5's, I also want to be able to drop a gear (split from OD to direct in a 13 spd) and get my rpm right back at my peak hp so I would need to get the truck geared to run 40" tall tires, with a 1:1 trans ratio and get the rpm in between 1600-1700. I have had trucks with this spec before and if you can hit your peak hp in direct at highway speed you can walk up a hill like a real truck should, get the rpm stuck down too low and dont have the right gear step in the trans to get it there and maintain speed and you start falling back and I dont care how fast I go as long as I can go the same speed up a hill.