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730 with 2.47 rear end gearing too tall?


mrrrl2

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Ok, kinda on-subject and kinda not. Why in blue blazes is R1 such a high gear on my 2 pedal Ultrashift ?? R1 is waaay higher than I would like it to be and R2 seems useless unless you lose all forward gears and have to do drive at highway speeds in reverse. I am much better at backing more smoothly than when I first got the truck but a steady and repeatable creep in reverse is not something I can count on. 2 pedaling it and finessing the throttle helps but Clutch Abuse still shows up more frequently than I would like. My rear ratio is 3.42....... Dolly's old brownie could sure improve backing my rig. Charlie

Don't ever tell a soldier that he doesn't understand the cost of war.

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Probably oughta' just lurk, but too tempted. If'n it was me, first thing I'd do is call the engine mfr w/ YOUR engine's SNO. Ask where the torque & HP curves are. THEN, analyze where you tow, and what speed would be a good fit for the roads & terrain you expect to drive. I'm geared so that 55-65 is 9th, and pulls great just under 65. After that, start looking at drive ratios, tire size, etc. With YOUR engine & YOUR drive ratio, you may be right where you need to be RPM at the speed you prefer. Exploring all the ratios is worthless unless you know exactly where your engine is designed to pull best, and that is taking into account any HP computer reset that will be on the engine MFR's records since it was built.

2000 Volvo 635 A/S, N-14 Cummins
"The Phoenix"
'03 KA 38KSWB

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This should be a topic at all rally events :-)

 

Imagine the boisterous discussions (and yes I'm still debating the 3.23 vs 3.08 locker rear end for my truck, but I'm gonna tow my fiver about 5,000 miles in March before deciding on anything)

2004 Volvo 630, Cummins ISX, Eaton 10 speed (air assist clutch), 3.71 3.07 rear locker, ET jr, 200" WB, GearMaster

2017 Forest River Sierra 372LOK

Full time June 2017

DW, 2 kids, and 2 dogs

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Dolly, Dolly, Dolly, you just ain't right........but I like you. Charlie

Charlie, Charlie, Charlie, you sound a lot like the Dollyomma.....she says of course I ain't right....what really matters is....how wrong I am....

 

Drive on.....(don't get to make right turns very often)

97 Freightshaker Century Cummins M11-370 / 1350 /10 spd / 3:08 /tandem/ 20ft Garage/ 30 ft Curtis Dune toybox with a removable horse-haul-module to transport Dolly-The-Painthorse to horse camps and trail heads all over the Western U S

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This should be a topic at all rally events :-)

 

Imagine the boisterous discussions (and yes I'm still debating the 3.23 vs 3.08 locker rear end for my truck, but I'm gonna tow my fiver about 5,000 miles in March before deciding on anything)

As long as we are resorting to too big wordz'$...("boisterous") it seems ok to crank the gear thread from ...."effect" of high-speed gearing to the "cause" of "oftentimes-disappointing" "effect" "less-than-Expeceted" MPG-gains (or sometimes loss of MPG).....

 

So....ya crawl out from the oil-dripper after stuffing the rear gear with a three tooth pinion and crank the old rig up to 77 mph and.... your mpg DROP'$ by one mpg, what the heck is up with that....you hauling too much Dr Pepper....shucks big5er know that there iz no such thing as too much Pepper.....or maybe ya got too much Mass-a-rotating.....well children I'd hazard a guess that Stekay is just about to wet himself wanting to jump on his soapbox about how ....."un-aero-un-dynamic" our trucks are (or NOT)...

 

Shucks we all know what a REAL truck looks like ..... everyone droolz over a old Pete with Ten inch stacks, Two chrome air cleaners the size of 55 gallon drums, and a front bumper the size and shape of a drive in movie screen....it's that "American-truck-look"....well children ....belly up to the diesel pumps and pay your fines.....

 

As a homeless pilot I was sometimes allowed hang around various wind tunnels and sometimes a Tunnel would have a....a..HDT inside the tunnel and heaven forbid some geek had filed-off many of the Rough edges and guess what...the aero-drag dropped off and the MPG Soared...but the truck looked.....Un-american...

 

Gee, as long as I am bateing poor old Stekay I might as well get him squeal'n on how "Un-aero-un-dynamic" the trailerz are we cobble on behind our trucks...shucks look at the roofs... it's so cluttered up there that a Navy Seal could not crawl up there....

 

Ok now I gotta go check that my Four foot wide curb side cargo door ain't flopping in the breeze....again..

 

Drive on....(HDT'$ have built in headwinds)

97 Freightshaker Century Cummins M11-370 / 1350 /10 spd / 3:08 /tandem/ 20ft Garage/ 30 ft Curtis Dune toybox with a removable horse-haul-module to transport Dolly-The-Painthorse to horse camps and trail heads all over the Western U S

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Don't forget that the majority of people are pulling the trailer 10-12 feet behind the cab. There is nothing aerodynamic about a 13' tall 8'6" wide flat front pushing thru the air.

Points to ponder-

Have new tires? Possible less fuel economy.

Highway tread VS off road lugs

Brand- My Hercules vs Michelins

Alie & Jim + 8 paws

2017 DRV Memphis 

BART- 1998 Volvo 610

Lil'ole 6cyl Cummins

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What would the mph at idle in reverse be with 2.47 / the actual trans / the actual tires?

1.73 MPH@ 650 RPM with 40" tire (504 revs/mi) Ultrashift 1:1

 

1.8 MPH for I-shift 1:1

"There are No Experts, Do the Math!"

2014 Freightliner Cascadia DD16 600hp  1850ft-lb  18spd  3.31  260"wb
SpaceCraft S-470
SKP #131740

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1.73 MPH@ 650 RPM with 40" tire (504 revs/mi) Ultrashift 1:1

 

1.8 MPH for I-shift 1:1

So..... Steve, at what RPM does the eye-$hift plop into high range in REVERSE....and at what mooock number does the V-machine attain flat out in REVERSE.....

 

Steve were onto something here.....the...RED BULLSHIPPER-REVERSE-RACE......one minor detail....do ya get mirror flutter past 75 knots in REVERSE ??

 

Drive on....(Fa$t back...)

97 Freightshaker Century Cummins M11-370 / 1350 /10 spd / 3:08 /tandem/ 20ft Garage/ 30 ft Curtis Dune toybox with a removable horse-haul-module to transport Dolly-The-Painthorse to horse camps and trail heads all over the Western U S

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One problem is that my Ultrashift won't go any where at idle in reverse....the clutch won't engage until I am at a tad over 800 rpm. I would prefer an Autoshift 3 pedal for creeping...then I could back at idle rpm. Hey, it is what it is, though. If you get the lurching and the cab rocking in the right rythym folks in the sleeper could have a good time without expending much energy......I could sell tickets for that ride. Charlie

Don't ever tell a soldier that he doesn't understand the cost of war.

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One problem is that my Ultrashift won't go any where at idle in reverse....the clutch won't engage until I am at a tad over 800 rpm. I would prefer an Autoshift 3 pedal for creeping...then I could back at idle rpm. Hey, it is what it is, though. If you get the lurching and the cab rocking in the right rythym folks in the sleeper could have a good time without expending much energy......I could sell tickets for that ride. Charlie

Charlie....your horning in on my tacky posting methods....

 

So while your getting rich selling tickets for your "REVERSE-ride" what are you going to do about the "clutch-abuse-light" flashing.....

 

The old Road-Rager in the Trolley ain't got no warning light....ya just get clutch smoke in your eyes....

 

Charlie....I still like ya...

 

Drive on....(how hots your clutch?)

97 Freightshaker Century Cummins M11-370 / 1350 /10 spd / 3:08 /tandem/ 20ft Garage/ 30 ft Curtis Dune toybox with a removable horse-haul-module to transport Dolly-The-Painthorse to horse camps and trail heads all over the Western U S

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1.5 and 1.9 ratios are coming. Hope y'all geezers can handle it! ;):P

Shucks Scrap....furget those darn decibel points and just go direct drive crank to wheel.....friend has a old geezer engineer that is pretty fast at stopping the Old Enterprise Diesel in the 1916 110ft tug AND pulling the REVERSE camshaft gear into engagement and then restart the old Enterprise in REVERSE rotation....forget the clutch....

 

Shucks just a little"hack" of the old ECM could get the ole wonder-diesel spinning backwards......so if'n ya got the thing running backwards would the DPF ....suck?

 

Drive on.....(Scraps in high....gear mode)

97 Freightshaker Century Cummins M11-370 / 1350 /10 spd / 3:08 /tandem/ 20ft Garage/ 30 ft Curtis Dune toybox with a removable horse-haul-module to transport Dolly-The-Painthorse to horse camps and trail heads all over the Western U S

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Y'kno when we built our first electric drive truck years ago I sent my spec into the axle rep and couldn't resist a bit of dry Scrap humor and sent him a negative axle ratio. Never heard back from him and after a couple weeks I was like crap i better fix this. But right as I started a tracking # came in, which was a bit more of an oh crap, but now I guess I just wait and see. Well a week later Fed Ex drops off a bus axle in my ratio. I met him and a few others for dinner a few days later and all he did was shake my hand and wink. Scrap hates it when he gets outsmarted!! LOL

 

Scraps in high gear mode........backwards. ;)

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Wow, it's going to take some super drive lines to handle the torque on them when connected to 1.9 to 1.5 drive ratio rears. Sounds like we may be approaching the point of diminishing returns as far as rear end ratios are concerned ?? Someone once told me "You buy horsepower but you drive torque." Charlie

Don't ever tell a soldier that he doesn't understand the cost of war.

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Yea the SPL350 d/l that got invented when 2.47 was invented a few years ago is no slouch either. The thing is a monster! The 1.5 is still in the way out there stuff though. You're right Charlie, I'm not sure how it is going to be done but it'll probably get mixed up in the DCT trans and the dual disconnect axles. 900 RPM cruise speed....... you won't hear anything but the plastic rattle!

 

This is all freeway flyer stuff though. In a go anywhere do anything truck overdrive still rules.

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  • 4 months later...

Ironically enough, the guy who never saw one is almost ready to pull the trigger on a 730 with a 2.47 ratio, 275-80R22.5 tires, with a non-overdrive iShift

Below are the RPM’s at various speeds in 12th gear:
70 mph @ 1487 RPM
68 mph @ 1450 RPM
66 mph @ 1400 RPM
65 mph @ 1380 RPM
63 mph @ 1350 RPM
61 mph @ 1300 RPM 

 

 

Av8r3400
2012 Volvo VNL 730 D13 iShift & 2021 Grand Design Momentum 397TH

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I'd rather die trying to live - Than live trying not to die.   -Leonard Perry

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On December 19, 2016 at 7:24 PM, Av8r3400 said:

I've been frequenting every truck list I can find and I have never seen a 2.47...

 

Where are you looking?

Most all fleet trucks built by Freightliner and Western star when used with the DT 12 transmission come with a 2:41 rear end now a days. 

2016 Western Star 5700xe (Pathfinder) DD15 555hp

w/12 speed automatic 3:05 diffs

2005 Newmar Mountain Aire 38RLPK

2 Great Danes

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17 hours ago, Heavymetal said:

Most all fleet trucks built by Freightliner and Western star when used with the DT 12 transmission come with a 2:41 rear end now a days. 

"If" direct drive which also adds a bit of efficiency vs. overdrive.

"There are No Experts, Do the Math!"

2014 Freightliner Cascadia DD16 600hp  1850ft-lb  18spd  3.31  260"wb
SpaceCraft S-470
SKP #131740

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3 hours ago, NoDirectionHome said:

"If" direct drive which also adds a bit of efficiency vs. overdrive.

They are running a fleet out of TN to LA on a 6x2 setup tuned to 400 hp with the 2:41 gears and they have all of the aero dynamic skirting on the tractors for testing. The trucks are 80k gross and average 12.5 mpg on the runs so they are doing something right with this combination. 

 

2016 Western Star 5700xe (Pathfinder) DD15 555hp

w/12 speed automatic 3:05 diffs

2005 Newmar Mountain Aire 38RLPK

2 Great Danes

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Yup, I have the same ratio in my Cascadia (overall)  3.31 rear x .73 OD= 2.416.  An incredibly quiet and powerful combination.  2.16's are coming this summer!

"There are No Experts, Do the Math!"

2014 Freightliner Cascadia DD16 600hp  1850ft-lb  18spd  3.31  260"wb
SpaceCraft S-470
SKP #131740

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Check out Cummins  PowerSpec V6.2.0.22 It will allow you to chose a cummins engine, trans, rears, tires and what  you want the truck to run. And tell you what each combo will do.

For Maximum Fuel Economy, select a gearing combination that will result in an engine speed of approximately 1350 - 1500 rpm at the vehicle's intended cruise speed (mph).
Customer Gearing Input
Intended Cruise Speed Gross Vehicle Weight Transmission Top Gear Ratio Low Gear Ratio Gear Down Ratio Number Of Gears Tire Size Rear Axle Ratio
60 mph 33 ,000 lbs 1, Eaton, RT-11613 12.56 1.159 13 547 rev/mi, , R227F 2.47, Meritor, MT-40-143MA-N
Customer Gearing Output
Engine RPM at Intended Speed Engine RPM at 65 mph Checkpoint Engine RPM in GearDown at Intended Speed 1566 Startability 38 Gradeability at Cruise Speed 5.35 Gradeability in Top Gear 5.55 1351 1464
Gearing Assessment

Please note: the assessment is based on the 'Intended Cruise Speed' and that evaluation at lower or higher road speeds for same gearing spec should be conducted if the vehicle will ever operate at speeds outside of the originally or main 'Intended Cruise Speed'.

 

Also if I go with a HDT and  can find the right combo. IT will be a 12.7 detroit, 13 speed OD with 2.47 rearend and run in direct at 62MPH. But when you want to step it up go to 13th OD at .64 and run flat out if you want to. The 13 speed will run all day in 12th with no issues. But still pull a Interstate grade in 12th gear at 55 MPH without an issues. But can move the RPM's up and run it at the speed limit if you want. 

There's a lot of OTR Owner Op's running this setup. And even grossing 75,000 lbs or more. It does good, but you can't order this truck. As the truck reps will try and tell you it will not work. But a lot of guys are running it. And making lot of cash off the extra MPG each month.

Pete

 

 


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