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Open Roads Forum  >  Tow Vehicles

 > Ford 6.7L 1050 ft lbs TQ at 1,600 rpm, 475 HP at 2,800 rpm

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Grit dog

Black Diamond, WA

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Posted: 10/03/19 10:12am Link  |  Quote  |  Print  |  Notify Moderator

12V. I’m not butthurt, just having fun!


"Yes Sir, Oct 10 1888, Those poor school children froze to death in their tracks. They did not even find them until Spring. Especially hard hit were the ones who had to trek uphill to school both ways, with no shoes." -Bert A.

Cummins12V98

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Posted: 10/03/19 10:29am Link  |  Quote  |  Print  |  Notify Moderator

Grit dog wrote:

12V. I’m not butthurt, just having fun!


Understood. [emoticon]


2015 RAM LongHorn 3500 Dually CrewCab 4X4 CUMMINS/AISIN RearAir 385HP/865TQ 4:10's
37,800# GCVWR "Towing Beast"

"HeavyWeight" B&W RVK3600

2016 MobileSuites 39TKSB3 highly "Elited" In the stable

2007.5 Mobile Suites 36 SB3 29,000# Combined SOLD

blofgren

Surrey, B.C.

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Posted: 10/03/19 09:07pm Link  |  Quote  |  Print  |  Notify Moderator

Grit dog wrote:

^True statement, but pursuant to ksss post, the Cummins has a smaller rpm range and more cogs would help the option and ability to pick the operating characteristics.
My G56 is a glorified 5 speed with granny gear and I can run 85-90 mph all day but she's screaming. And loaded heavy, I sometimes have to settle on a particular speed that I can pull and keep egts in check vs picking the speed I want and having a gear to accommodate it.
The low rpm range of the C will benefit greatly from more cogs. Moreso than the higher revving V8s in this respect, IMO. More IS better in this case. For everyone.


Agreed. I too have had issues when loaded heavy on steep grades with no ability to get a run at it where I’m caught between 3rd and 4th gear on the G56; lots of power in 3rd but can’t quite hold 4th. Oh well, the old girl is reliable and paid for! [emoticon]


2013 Ram 3500 Megacab DRW Laramie 4x4, 6.7L Cummins, G56, 3.73, Maximum Steel, black lthr, RAM 20k sliding hitch, Retrax, Linex, and a bunch of options incl. cargo camera
2008 Corsair Excella Platinum 34.5 CKTS fifth wheel with winter package & disc brakes

ShinerBock

SATX

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Posted: 10/04/19 08:17am Link  |  Quote  |  Print  |  Notify Moderator

blofgren wrote:

Grit dog wrote:

^True statement, but pursuant to ksss post, the Cummins has a smaller rpm range and more cogs would help the option and ability to pick the operating characteristics.
My G56 is a glorified 5 speed with granny gear and I can run 85-90 mph all day but she's screaming. And loaded heavy, I sometimes have to settle on a particular speed that I can pull and keep egts in check vs picking the speed I want and having a gear to accommodate it.
The low rpm range of the C will benefit greatly from more cogs. Moreso than the higher revving V8s in this respect, IMO. More IS better in this case. For everyone.


Agreed. I too have had issues when loaded heavy on steep grades with no ability to get a run at it where I’m caught between 3rd and 4th gear on the G56; lots of power in 3rd but can’t quite hold 4th. Oh well, the old girl is reliable and paid for! [emoticon]


That is because of the gear ratios of the G56. Due to having a granny gear, you essentially have a 5 speed with one overdrive and the rest of the gears are spaced out too far apart to accommodate. The 68RFE/Aisin has less of a spread and has two overdrive gears.

G56 spread
1st/2nd:-45%
2nd/3rd:-40%
3rd/4th:-34%
4th/5th:-24%
5th/6th:-26%

68RFE spread
1st/2nd:-43%
2nd/3rd:-23%
3rd/4th:-29%
4th/5th:-18%
5th/6th:-23%

Aisin spread
1st/2nd:-46%
2nd/3rd:-32%
3rd/4th:-25%
4th/5th:-23%
5th/6th:-18%

* This post was edited 10/04/19 08:25am by ShinerBock *

Grit dog

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Posted: 10/04/19 08:43am Link  |  Quote  |  Print  |  Notify Moderator

^ The not quite granny low first gear in the G56 is the perfect ratio for coming off the line with a heavy load and nice for creeping around at an idle on rough roads, etc.
2nd through 5th are also a good spread (at least with the power I have with a tune) for most any trailer. Never pulled more than 16-18k with it though and only a couple times, but the gear splits were "good enough" to keep in the power band. Where the G lacks is it desperately needs a 7th gear, at least with the 3.73s or deeper gears. Never drove a 3.42/G56 truck.
6th could be geared just a bit lower and 7th for empty road trips across Montana.
Over 10 years and 170k miles later, I still randomly reach for 7th gear after hours of bombing down the highway at 2500-2600rpms! Still haven't found it....

* This post was edited 10/04/19 09:00am by Grit dog *

ShinerBock

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Posted: 10/04/19 09:15am Link  |  Quote  |  Print  |  Notify Moderator

Yea, the 6th gear of the G56 is right smack dab in the middle ratio wise between 5th and 6th of the 68RFE and Aisin. And the torque multiplication of the torque converter in 1st and 2nd gears allows for taller gear ratios in the autos. You can't do this on a manual since the clutch does not multiply torque coming from the engine. Although I would still love to have a manual over an auto, but the wife put her foot down on that. She would not be able to drive me home from the farm when I have had too many.

blofgren

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Posted: 10/04/19 06:25pm Link  |  Quote  |  Print  |  Notify Moderator

Grit dog wrote:

^ The not quite granny low first gear in the G56 is the perfect ratio for coming off the line with a heavy load and nice for creeping around at an idle on rough roads, etc.
2nd through 5th are also a good spread (at least with the power I have with a tune) for most any trailer. Never pulled more than 16-18k with it though and only a couple times, but the gear splits were "good enough" to keep in the power band. Where the G lacks is it desperately needs a 7th gear, at least with the 3.73s or deeper gears. Never drove a 3.42/G56 truck.
6th could be geared just a bit lower and 7th for empty road trips across Montana.
Over 10 years and 170k miles later, I still randomly reach for 7th gear after hours of bombing down the highway at 2500-2600rpms! Still haven't found it....


Most of the time the gear splits are fine to keep mine in the power band too, but there is the odd time on a really tough pull where I get caught in the middle (I think it’s only happened twice). Once I upgrade the clutch I’m thinking off adding a towing tune so maybe that will help. I agree that a 7th gear would be nice for the highway.

Overall I still really like the stick, though. My wife doesn’t like driving it either but she gets by the very odd time it’s required....[emoticon]

burningman

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Posted: 10/06/19 12:12pm Link  |  Quote  |  Print  |  Notify Moderator

The extra gears probably do help. I have a Gear Vendors overdrive in my old Dodge Cummins and 3rd+OD is a great pulling gear th struck didn’t originally have.

But I also think ALL of this is ridiculous! When you have a 30,000 pound trailer, you’re in big-truck territory. Not pickup truck territory. And you need a CDL.
My 385 (Pete) made 378 at the wheels on a dyno. It can run at full throttle indefinitely, uphill under a load and the EGT doesn’t get over 700.
That’s what you need to pull huge weight up mountain s


2017 Northern Lite 10-2 EX CD SE
99 Ram 4x4 Dually Cummins
A whole lot more fuel, a whole lot more boost.
4.10 gears, Gear Vendors overdrive, exhaust brake
Built auto, triple disc, billet shafts.
Kelderman Air Ride, Helwig sway bar.


Cummins12V98

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Posted: 10/06/19 01:09pm Link  |  Quote  |  Print  |  Notify Moderator

burningman wrote:

The extra gears probably do help. I have a Gear Vendors overdrive in my old Dodge Cummins and 3rd+OD is a great pulling gear th struck didn’t originally have.

But I also think ALL of this is ridiculous! When you have a 30,000 pound trailer, you’re in big-truck territory. Not pickup truck territory. And you need a CDL.
My 385 (Pete) made 378 at the wheels on a dyno. It can run at full throttle indefinitely, uphill under a load and the EGT doesn’t get over 700.
That’s what you need to pull huge weight up mountain s


Trucks percentage of overall load is no more and more likely less than a Semi.

Your 4 speed auto is not a great example as there is a huge gap between 3rd and 4th. The modern 6 speed auto is very evenly spaced.

RoyJ

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Posted: 10/06/19 02:18pm Link  |  Quote  |  Print  |  Notify Moderator

A better comparison would be tow truck's total GAWRs vs total towing weight.

A tractor typically have 44k rears with 13k fronts. That's 57k for 80k combined weight.

A dually has 10k rears and 6k fronts, at best. That's 16k for 40k+ combined.

So the semi tractor has a much better running gear toughness to GCW ratio.

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