Jump to content

730 with 2.47 rear end gearing too tall?


mrrrl2

Recommended Posts

I see a lot of the 730's with D13 currently on the market with 2.47 rear ends. Is this too tall for most of the users here? I did some searching and saw a video Greg (RV Hauler WILSON Intro Model 730 ishift with 2.64 rear end ratio) did on a 730 with 2.64 gearing but is 2.47 just too tall? I understand that there are a lot of variables here and that there maybe several different iShift models with different gearbox ratios. Currently looking for a 730, adding Smart on back with 36-38' 5th wheel just not sure about this tall of a rear end.

 

Any one here with this rear end?

Link to comment
Share on other sites

  • Replies 51
  • Created
  • Last Reply

Couple of things: Whatcha haul'in? Is the I-Shift an ATO? (overdrive version) What year is the truck? What's the engine tune? (HP/Torque)

I always find these conversations amusing, especially when people say you need more power for the mountains.

"There are No Experts, Do the Math!"

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

Link to comment
Share on other sites

You've seen multiple trucks with 2.47 rear ends? Most everything I see out there is in the 3.08 and up. Sometimes a 2.64 pops up, but I don't think I've seen any 2.47 pop up? Interesting. It seems for a truck carrying 80k lbs, that would be a high ratio, but maybe not too bad for the weights most carry here?

 

I noticed on the older trucks, you seem to see even higher ratios, with many in the 3.50-3.73 range. I guess they are getting more efficient as they get newer.

Dan (Class of 2017) - 2012 Ram 3500 & 2005 Alpenlite Valhalla 29RK
Contact me at rvsolarconsulting.com or Two Wheel Ramblin

Link to comment
Share on other sites

So let me help you out here. 3.08 x .78 (I-shift overdrive ratio) = 2.40 The 2.47 is "usually" a direct drive transmission. The new dual torque engines also help make up the difference.

"There are No Experts, Do the Math!"

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

Link to comment
Share on other sites

You've seen multiple trucks with 2.47 rear ends? Most everything I see out there is in the 3.08 and up. Sometimes a 2.64 pops up, but I don't think I've seen any 2.47 pop up? Interesting. It seems for a truck carrying 80k lbs, that would be a high ratio, but maybe not too bad for the weights most carry here?

 

I noticed on the older trucks, you seem to see even higher ratios, with many in the 3.50-3.73 range. I guess they are getting more efficient as they get newer.

 

The fleet trucks coming out for Freightliner and Western Star are set up with a 400hp DD15 the new DT12 transmission and 2:41 rear ends. The new drive line is all built by Detroit and all work together to increase mileage. They have a few really good videos on this setup. The afore mentioned drive line averages 9.3 mpg while hauling a GVW of 79k lbs on a 2,400 mile cross country trip.

2016 Western Star 5700xe (Pathfinder) DD15 555hp

w/12 speed automatic 3:05 diffs

2005 Newmar Mountain Aire 38RLPK

2 Great Danes

Link to comment
Share on other sites

Discussing the rear end ratio without the second half of the discussion-the transmission and it's ratios/spec's is a fruitless endeavor. The torque characteristics of the engine is also part of the equation. The only concern I would have with a tall ratio like a 2.64 or 2.47 is start ability, i.e pulling out a an inclined dock with 80,000k gross. And the manufacturer is well aware of that possibility and has designed a transmission 1st or 2nd gear with a gear reduction to address the need.

The current school of thought, having the transmission in a direct drive(straight thru) configuration which is more fuel efficient than an overdrive arrangement has been popular for some time.

Since the HDT/RV application doesn't call for weights anything close to the original truck design, I wouldn't be too concerned about it.

Jeff Beyer temporarily retired from Trailer Transit
2000 Freightliner Argosy Cabover
2008 Work and Play 34FK
Homebase NW Indiana, no longer full time

Link to comment
Share on other sites

 

Since the HDT/RV application doesn't call for weights anything close to the original truck design, I wouldn't be too concerned about it.

I'm with Jeff on this. It will work for you, if you have reasonable expectations. However, It MAY NOT work well for you depending on your average driving speed on open roads. For example, You may like to drive at 63 mph like I do. But the truck gearing/trans may not like to be in 12th gear at that speed, and keep you in 11th. OR it may put you back in 11th on ANY mild grade. That may require you to drive at 68mph, instead, to avoid that issue. YOU MUST DRIVE THE TRUCK to determine this quirk, and if it will work for you. No simulator is going to get that answer right.

Jack & Danielle Mayer #60376 Lifetime Member
Living on the road since 2000

PLEASE no PM's. Email me. jackdanmayer AT gmail
2016 DRV Houston 44' 5er (we still have it)
2022 New Horizons 43' 5er
2016 Itasca 27N 28' motorhome 
2019 Volvo 860, D13 455/1850, 236" wb, I-Shift, battery-based APU
No truck at the moment - we use one of our demo units
2016 smart Passion, piggyback on the truck
-------------------------------------------------------------------------
See our website for info on New Horizons 5th wheels, HDTs as tow vehicles, communications on the road, and use of solar power
www.jackdanmayer.com
Principal in RVH Lifestyles. RVH-Lifestyles.com

Link to comment
Share on other sites

I'm with Jeff on this. It will work for you, if you have reasonable expectations. However, It MAY NOT work well for you depending on your average driving speed on open roads. For example, You may like to drive at 63 mph like I do. But the truck gearing/trans may not like to be in 12th gear at that speed, and keep you in 11th. OR it may put you back in 11th on ANY mild grade. That may require you to drive at 68mph, instead, to avoid that issue. YOU MUST DRIVE THE TRUCK to determine this quirk, and if it will work for you. No simulator is going to get that answer right.

Jack you bring up some good points and I will throw in my two cents worth and it relates to Jeff's comments regarding transmissions as well.

 

The Dollytrolley is a old Shaker with a M11 Cummins, 3:08 drivers AND a 10 speed Road-Rager tranny .....at first glance this combination would seem to be a economical HDT RV rig for cruising down the highway....and so far this has been the case....However, as Jeff mentioned sometimes low speed operations are "compromised" and with the Dollytrolley the tranny has a high speed reverse gear and IF the bone-head driver bumbles into high range reverse the Trolley could easily out run big5er'$ DOT rig...in REVERSE...

 

High-speed reverse is a pain in the keister so I simply engage in chronic clutch abuse when I need creep-speeds in REVERSE....

 

Couple of times I have pondered cobbling a brownie four speed behind the Road-Rager but do I really need FORTY gears to mismanage....answer..NO..

 

Like Jack says RV'$ are a study in .... compromise...

 

Drive on.....(what's your gears today)

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

Link to comment
Share on other sites

I understand that there are a lot of variables here and that there maybe several different iShift models with different gearbox ratios.

As I understand it, the iShift has always had the same gearing. The only variable as Stekay pointed out is the AT vs. ATO (overdrive vs. non-overdrive): the splitter can be "plumbed" two different ways, as an overdrive or as an underdrive. If it's overdrive, 11th is direct and 12th is overdrive.Otherwise, 12th is direct. Volvo was/is proud of the fact that the iShift has consistent ~27% gear spacing across the entire range, something that can't be said for the 9/13/18 crowd.

Link to comment
Share on other sites

So, why has no one asked what tire size? The difference between a 22.5 and a 24.5 can easily approach 10% circumference, depending on aspect ratio and width.

 

Changing tires is WAY cheaper than changing ring/pinions.

KW T-680, POPEMOBILE
Newmar X-Aire, VATICAN
Lots of old motorcycles, Moto Guzzi Griso and Spyder F3 currently in the front row
Young enough to play in the dirt as a retired farmer.
contact me at rickeieio1@comcast.net

Link to comment
Share on other sites

Because you're talking about changing Tires & Rims times 10 along with the fact that 24.5's are rather rare if you need service. So let's say we go $500/tire then another $150/wheel even with your trade ins you're looking at a boat load of cash even if you're singled. So no, not way cheaper. Also, noone said anything about "changing ratio'

"There are No Experts, Do the Math!"

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

Link to comment
Share on other sites

True enough. I don't know where the OP is looking, geographicly, for a truck. In some areas, 24.5s are not unusual. And, I was not assuming new tires and wheels, or a count of 10. Swapping wheels at a dealer might be pretty cheap, if you're buying the truck there.

KW T-680, POPEMOBILE
Newmar X-Aire, VATICAN
Lots of old motorcycles, Moto Guzzi Griso and Spyder F3 currently in the front row
Young enough to play in the dirt as a retired farmer.
contact me at rickeieio1@comcast.net

Link to comment
Share on other sites

I'm running 2.64 with 24.5 rubber and direct drive tranny , it just about perfect for me, only down fall reverse is pretty quick just don't need much throttle when backing up

2014 jayco siesmic 3914

1998 volvo 610, singled short ( bought in 2005)

14 speed volvo tranny

2014 Toyota yaris

Link to comment
Share on other sites

Bigger tires eat mpg. More rotating mass.

Ya know.....inquiring minds want to know Glenn.... just wonder what the dynamic(z) are between 22.5'$ and 24.5'$....this homework assignment might be perfect for ....Stekay. ...

 

We could sling around some hot terms like...coo-efffecntz-fiction, monimentz-0f-ontererza, and biaza-verza-raodial-plyei-internactional+ gravitational -xttatresteral-forcez'$..... and a bunch of engineering-geek-terms as space permits...

 

Talk'n tires often leads to.....a well "rounded" discussion (I could not resist the punn).

 

Drive on....(into the engineering...vortex)??????♎❔〰❎➕➖➗☢

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

Link to comment
Share on other sites

Guys really like big tires on ldt trucks. They all loose mpg and pulling power.True our trucks have power to spare but the same happens. Just not as pronounced on our trucks. I have considered doing this. My ratio 3:50ish. But I do not believe I would gain any mpg due to the increased rotating mass.

2003 Teton Grand Freedom towed with 2006 Freightliner Century 120 across the beautiful USA welding pipe.https://photos.app.goo.gl/O32ZjgzSzgK7LAyt1

Link to comment
Share on other sites

Dolly, howd'ya fergit radius of gyration?

Shucks big boy...ya got on that de-tail, so.....will you record just raw-data or....will ya kalkulate it in half-A$$ed-fornieer-Log-$cale....

 

Don't forget themtheree db'z an powers of perswaziatinz...

 

How could ya have more fun with your clothes on.....

 

Drive on....(Stekay Is getting in da groove)

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

Link to comment
Share on other sites

My, oh my....... In the end, Sammy Hagar mentioned something about Mental Mast............. Talking hypothetical mileage is just that. In the real world, your driving habits will decide which gearing works best, and whether you are happy with your mpg.

 

I have a son-in-law that had to have a diesel Touareg, for the mileage. The he drives like a bat-out-of-hades, and gets crap mileage in spite of his aftermarket air filter (which violated the warranty) and all the other doo-hickeys he's had to add. These trucks are no different. I'd bet someone like BroncoHauler could extract decnt mileage out of the worst truck in this group, v. someone in a hurry to get there.

KW T-680, POPEMOBILE
Newmar X-Aire, VATICAN
Lots of old motorcycles, Moto Guzzi Griso and Spyder F3 currently in the front row
Young enough to play in the dirt as a retired farmer.
contact me at rickeieio1@comcast.net

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.


RVers Online University

campgroundviews.com

RV Destinations

Find out more or sign up for Escapees RV'ers Bootcamp.

Advertise your product or service here.

The Rvers- Now Streaming

RVTravel.com Logo



×
×
  • Create New...