Gearing/info seeking

[Lonestar10]

So recent was able to dig my data plate for my rears out of it's paint tomb. Found dealership advertising of 3.55s was wrong. I have 3.36s and 65-67mph is around 1300 rpm and around 70 is 1400ish. I would say my loaded miles is 95% at 70k to 80k lbs flatbed with about 32000=empty weight at 1/2 tanks.

So question is what might a better gear be for my cm871 13sp. With 500hp mm tune. My cruise speed is 65-67mph when loaded and at 80k she feels like a snail getting there and almost any incline or breeze makes her want to go-to 30+ lbs of boost loaded. Winter fuel average is 4mpg.

I did have 2cylinders with bad exhaust gaskets and they were fixed yesterday along with scoping cylinders through injector holes all cylinders show perfect crosshatches for 180k on overhaul. So I'm hoping I see some improvement from exhaust being sealed up goodntight when I get back from cancun.

Previous work in last 6mo
6 injectors
Imap, Delta p, exh press
All 4 actuators
Fuel shutoff solenoid
Crank/cam sensors
Turbo and actuator 130k ago
15k oil changes rot 15/40
Mm tune
With cold weather idling uses about 1gal oil in 15k, about 1/2 gal or less when I don't have to idle.
Think that's it.

If there's anything else I should look at please let me know.

[hhow55]

(03-02-2019 )Lonestar10 Wrote:  So recent was able to dig my data plate for my rears out of it's paint tomb. Found dealership advertising of 3.55s was wrong. I have 3.36s and 65-67mph is around 1300 rpm and around 70 is 1400ish. I would say my loaded miles is 95% at 70k to 80k lbs flatbed with about 32000=empty weight at 1/2 tanks.

So question is what might a better gear be for my cm871 13sp. With 500hp mm tune. My cruise speed is 65-67mph when loaded and at 80k she feels like a snail getting there and almost any incline or breeze makes her want to go-to 30+ lbs of boost loaded. Winter fuel average is 4mpg.

I did have 2cylinders with bad exhaust gaskets and they were fixed yesterday along with scoping cylinders through injector holes all cylinders show perfect crosshatches for 180k on overhaul. So I'm hoping I see some improvement from exhaust being sealed up goodntight when I get back from cancun.

Previous work in last 6mo
6 injectors
Imap, Delta p, exh press
All 4 actuators
Fuel shutoff solenoid
Crank/cam sensors
Turbo and actuator 130k ago
15k oil changes rot 15/40
Mm tune
Think that's it.

If there's anything else I should look at please let me know.

3.70 rear

[Rawze]

3:70's (or 3:79's).

http://rawze.com/forums/showthread.php?t...3#pid17353

[JMBT]

3:70’s would be the fastest I would want. 3:90’s if you ever plan to go over gross.

You mentioned oil usage “with cold weather idling issues”, What are the cold weather idle issues you are talking about?? Just curious, thanks.

[Lonestar10]

Been below 0 and lots of wind so during my sun-fri for past few weeks there hasn't been much apu time. As far as issues have none

[ynot]

3.70, or 3.73's depending on who makes your rears, sitting on 11r22.5 would do great but those are more of a 60-64mph gears, 3.55 would prob be more suited too your speed range, but switching from 3.36 too 3.55 is kinda pricey for the small gains unless they are needing a rebuild anyway

I'd slow down an start running split back in 12th get the rpms up a bit should help some with at speed pulling power, the other thing I'd do is next tire change drop down too low pro's that'll bump your gear ratio up close too 3.55's

[Lonestar10]

I'm currently on 11r22.5s. and I do tend to run 12th at about 1550ish. When I'm under a load of shingles out of Shakopee MN at 79-80k it almost wants to run 25-30lbs boost down 169/60 to Worthington and seems to do around 17-22lbs the rest of the way to Sioux City on what seems to be mostly flats.

I'm hoping that new manifold gaskets brings those numbers down since I had 2 cylinders leaking. Took idling alot in the cold to find the problem with fuel or oil slobbering up on side of engine my tune seems to run real clean in the cold as I can't get any grey/black from stacks driving or neutral.

[ynot]

Do you have any software too watch your motor? The rear gears you can't do anything about at the moment, but with cterm, you can watch what your motor is doing, the fuel used, torque being out down, VGT percentages ect. an use what your seeing too work around your gears an hopefully up your fuel milage.

Not gonna lie it's probably gonna involve slowing down though since its winter an we got the shi#t winter fuel too deal with, an the dense cold air that's like a wall too plow through, so the slower you go the less your fighting the wall.

[Lonestar10]

Yes I have tr!m and insite. It's discouraging my dad's cm870 t600 13sp 3.55s is stock 500hp he runs 70 getting 5.5-6mpg on same loads