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cgallamore

Gear Ratio

53 posts in this topic

i had a 13 spd overdrive with 373 ratio, in the 55mph states it turned 1200 rpm's it lugged to much

i now have a 13spd no overdrive and 393 ratio it seems to do a great job at any speed.and it gets better mpg at 70 mph than 60 mph. and pulls like it's pissed off.

it would seem if i had overdrive i would need 411 ratio.

i see trucks with overdrive and 342 ratio how can this work????????

i know the guy's specing these trucks are smarter than me, but what am i missing????????

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What model transmission do you have? I didn't know there was any recent 15-1600 series 13 speeds that did not have overdrive.

Dave

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What model transmission do you have? I didn't know there was any recent 15-1600 series 13 speeds that did not have overdrive.

Dave

i dont have the build sheet on my truck, i understand it has a slight overdrive, but not like some of the stuff thats out there.

i guess i should have made my question more clear. i cant figure how to drive a truck that you have to wind up that tight to get it in overdrive, and at the slightest grade its lugging its guts out??????

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Get the numbers off the side of the transmission, rear ratio and tire size. Then we can help you.

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a friend of mine got an 06 pete. i had never driven one so i took it down the road and back about 20 miles.

dont know anything about them but was told it had a 475 cummings and 10spd overdrive i had to wind it like hell to get it in o/d then at first hill it fell on it's face, so rather than saying hey buddy i think your new truck is a piece of crap, i thought i would get on here and see what im doing wrong.

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Get the numbers off the side of the transmission, rear ratio and tire size. Then we can help you.

mine is fine wouldn't change a thing

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That's the beauty of a 10sp. I think the newer ISX's and especially the Cat Accert motors have a very narrow powerband and the high(numericaly low) gear ratio is needed to keep the motor at 1300-1400rpm at cruising speed to get decent mpg.

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if its a B series Fuller it would have a .86 OD in high hear roughly the same as a half gear down in a A series, pretty rare, I was under the assumption your Rawhide had the Mack 13

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if its a B series Fuller it would have a .86 OD in high hear roughly the same as a half gear down in a A series, pretty rare, I was under the assumption your Rawhide had the Mack 13

yes my rawhide has a mack 13

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That's the beauty of a 10sp. I think the newer ISX's and especially the Cat Accert motors have a very narrow powerband and the high(numericaly low) gear ratio is needed to keep the motor at 1300-1400rpm at cruising speed to get decent mpg.

so you are saying the new macks with 342 gears and a 10spd o/d are that big of a pos.

the shut down on the pete is 69mph so i couldn't get a run at anything

it feels like it needs to be in 9th gear exept when decending a hill. uless you want to feel like you have an engine brake then you have to run in 9th also??????????????

i cant see building a truck that wacked out so i must be driving it wrong??????

65mph is around 12oo rpm's

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i now have a 13spd no overdrive and 393 ratio it seems to do a great job at any speed.and it gets better mpg at 70 mph than 60 mph. and pulls like it's pissed off.

If you're running 11R 22.5 tires, with a direct drive 13 speed and 3.93 gears engine's turning 2,200 rpm @ 70 mph.

My guess is you have an overdrive. :idunno:

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My guess is that if it has more than one tooth on top, and two on the bottom, (like me) I'll never understand either.

Rob

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yes my rawhide has a mack 13

that would be a double over box .71 hi gear, I would think fuller 13 and 3.70's and 3.94 with a Mack 13 would be geared pretty close to the same as far as rpms in high gears, but I could be wrong

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so you are saying the new macks with 342 gears and a 10spd o/d are that big of a pos.

the shut down on the pete is 69mph so i couldn't get a run at anything

it feels like it needs to be in 9th gear exept when decending a hill. uless you want to feel like you have an engine brake then you have to run in 9th also??????????????

i cant see building a truck that wacked out so i must be driving it wrong??????

65mph is around 12oo rpm's

I was being sarcastic about the 10sp. They don't have many options when it comes to cruising speed, you either wind the $hit out of it or lug it. I drove 10 speeds for a few years, now I have an 18sp and love it...there's a gear wherever I need it.

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that would be a double over box .71 hi gear, I would think fuller 13 and 3.70's and 3.94 with a Mack 13 would be geared pretty close to the same as far as rpms in high gears, but I could be wrong

with a fuller 13 and 373 55mph about 1200 rpm's

the mack 13 and 393 55mph about 1300 rpm's

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with a fuller 13 and 373 55mph about 1200 rpm's

the mack 13 and 393 55mph about 1300 rpm's

I wanna say the Fuller prolly has a .73 OD. The Mack is a .71. The only detail you are omitting is the tire size, which makes a difference. 11R24.5's are roughly 44". LP 24.5's and 11R22.5's are both around 42". LP 22.5's are going to be in the 40" ballpark.

http://www.4lo.com/calc/gearratio.htm

I would guess the Fuller 13/3.73 is riding on either LP 24.5's or 11R22.5's...either way would put the truck at 55 mph @ 1200 rpm.

I would also guess the Mack 13/3.93 is riding on LP 22.5's, which would put the truck at 55 mph @ 1300 rpm.

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I was being sarcastic about the 10sp. They don't have many options when it comes to cruising speed, you either wind the $hit out of it or lug it. I drove 10 speeds for a few years, now I have an 18sp and love it...there's a gear wherever I need it.

Yup. My thoughts exactly. I just wish I had more gears in reverse....wouldn't mind a lower "low" either. I wonder why they don't move 4th gear to the high range "low" position, move all of the low range gears up one hole, and add a lower "low" gear? ...or better yet, why can't they just put a splitter on the T310ME to get the 20 forward gears w/ multiple shift possibilities in reverse, too B)

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Yup. My thoughts exactly. I just wish I had more gears in reverse....wouldn't mind a lower "low" either. I wonder why they don't move 4th gear to the high range "low" position, move all of the low range gears up one hole, and add a lower "low" gear? ...or better yet, why can't they just put a splitter on the T310ME to get the 20 forward gears w/ multiple shift possibilities in reverse, too B)

Why not just slide some 2 speed rear ends underneath your truck? 36 speeds!

I wish my 18sp had a normal speed reverse...it just creeps.

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Why not just slide some 2 speed rear ends underneath your truck? 36 speeds!

I wish my 18sp had a normal speed reverse...it just creeps.

....'cuz Mack don't have any :rolleyes:

Seriously, if I were spec'ing any OTHER brand truck, I'd do it....but why buy a Mack if'n ya ain't got a Mack drivetrain? :unsure:

Hell, a DT521/RT521 tandem with a 3.70/5.04 gearset riding on a 52K Hendrickson AR2 air walking beam suspension would be a pretty sweet setup...'specially with 600+ HP under the hood and an 18 speed transmission and some aggressive tires like Michelin's XDE M/S* in 11R24.5 B)

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....'cuz Mack don't have any :rolleyes:

Seriously, if I were spec'ing any OTHER brand truck, I'd do it....but why buy a Mack if'n ya ain't got a Mack drivetrain? :unsure:

Hell, a DT521/RT521 tandem with a 3.70/5.04 gearset riding on a 52K Hendrickson AR2 air walking beam suspension would be a pretty sweet setup...'specially with 600+ HP under the hood and an 18 speed transmission and some aggressive tires like Michelin's XDE M/S* in 11R24.5 B)

...yeah, I'm good at thinking about spending money I ain't got :wacko:

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....'cuz Mack don't have any :rolleyes:

Seriously, if I were spec'ing any OTHER brand truck, I'd do it....but why buy a Mack if'n ya ain't got a Mack drivetrain? :unsure:

Hell, a DT521/RT521 tandem with a 3.70/5.04 gearset riding on a 52K Hendrickson AR2 air walking beam suspension would be a pretty sweet setup...'specially with 600+ HP under the hood and an 18 speed transmission and some aggressive tires like Michelin's XDE M/S* in 11R24.5 B)

Where the hell do you go where that's needed??? lol

I'd be happy with full lockers.....aaannnnnndddd 600+hp.

I just spent the afternoon putting a new radiator in the truck, couple new air horns...next is to rig up the fog light switch for my 'chicken' lights and then some full fenders...

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Where the hell do you go where that's needed??? lol

I'd be happy with full lockers.....aaannnnnndddd 600+hp.

I just spent the afternoon putting a new radiator in the truck, couple new air horns...next is to rig up the fog light switch for my 'chicken' lights and then some full fenders...

oops...fergot about the full lockers :pat: Gotta have it on 2 separate switches, though...one for the power divider, and a second to lock the center diffs for them situations where ya need all the traction ya can scrape together ta git ya out of a jam.

....and every time I have to dig my chain out of my side box for a pull, I'm wishing I had a better set-up. :angry:

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oops...fergot about the full lockers :pat: Gotta have it on 2 separate switches, though...one for the power divider, and a second to lock the center diffs for them situations where ya need all the traction ya can scrape together ta git ya out of a jam.

....and every time I have to dig my chain out of my side box for a pull, I'm wishing I had a better set-up. :angry:

When in doubt tach it out!

That'll be the two main things I look for in my next truck...lockers and some wheelie poppin horsepower..maybe a jake brake thats worth a shit.

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When in doubt tach it out!

I prefer the "stick it in the low hole and crawl it out" approach....less likely to tear shit up if/when a wheel finds traction. I hate spinning my wheels.

..maybe a jake brake thats worth a shit.

goodpost.gif

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I wanna say the Fuller prolly has a .73 OD. The Mack is a .71. The only detail you are omitting is the tire size, which makes a difference. 11R24.5's are roughly 44". LP 24.5's and 11R22.5's are both around 42". LP 22.5's are going to be in the 40" ballpark.

http://www.4lo.com/calc/gearratio.htm

I would guess the Fuller 13/3.73 is riding on either LP 24.5's or 11R22.5's...either way would put the truck at 55 mph @ 1200 rpm.

I would also guess the Mack 13/3.93 is riding on LP 22.5's, which would put the truck at 55 mph @ 1300 rpm.

they are both on 11r 22.5

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