Re: How much does rear gear ratio effect HWY gas mileage?
[Re: 360view]
#2510904
06/20/18 04:52 PM
06/20/18 04:52 PM
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Joined: Dec 2007
Posts: 2,683 Des Moines IA
Soopernaut
master
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master
Joined: Dec 2007
Posts: 2,683
Des Moines IA
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Yes Yes. There are so many variables but throttle input seems to have the biggest effect on the gauge reading. I can have a wide difference in MPGs at the same speed on a relatively flat highway. I do most of my driving in the city and can get better mileage than I get at times on the highway, if it is not stop and go. If I drive 40-60 MPH on a flat road with no stops I can get MPG readings of near 30 MPG. At 70-75 MPH I generally get low 20s, but at those speeds the road can have more changes which affect the readings. Overall city MPGs average in the upper teens. Cold weather and stop and go traffic can have a large effect on the city readings. I do have 3.73 gears which could affect the highway mileage some and perhaps benefit city driving. Some others have mentioned sustained MPGs in the mid 20s with the 2.7L. I have an XLT which does not have a boost gauge standard. Higher trim levels have the boost gauge and I'm sure some have added it to their XL/XLT trucks. Many of the F150 forum members claim lower MPGs with the 5.0, which seems to be the consensus. The 3.5 Ecoboost is between the 5.0 and 2.7 in terms of mileage. The 5.0 with the 10 speed seems to be a better match than it is with the 6 speed.
1970 Dodge d100/eventually going on a 77 D100 frame
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Re: How much does rear gear ratio effect HWY gas mileage?
[Re: ragtop]
#2511282
06/21/18 12:40 PM
06/21/18 12:40 PM
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Joined: Jun 2006
Posts: 441 Frederick , MD
GibW340
mopar
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mopar
Joined: Jun 2006
Posts: 441
Frederick , MD
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Anyone measured there highway gas mileage before and after a gear swap? If so, can you post some numbers. Even if it was somewhat steady state rural road driving. I know that city or around town driving won't be hardly effected by gear ratio. Thank you. A factor to consider is where and how you are driving- Long distances at higher speed would be better with lower ratioo More stop and go low speed- somewhere the higher # ration would be more effiective it would seem
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Re: How much does rear gear ratio effect HWY gas mileage?
[Re: ragtop]
#2512071
06/23/18 10:06 AM
06/23/18 10:06 AM
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Joined: Jan 2006
Posts: 8,162 USA
360view
Moparts resident spammer
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Moparts resident spammer
Joined: Jan 2006
Posts: 8,162
USA
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http://www.hotrod.com/articles/1010sr-quick-change-rear-end/Being able to quickly change diff ratios could answer a lot of questions similar to those in these posts. In these days of CNC it would also seems that making custom planetary gear sets to go inside Chrysler 46/47/48 OD units would not be that hard or expensive. Swapping OD units would just slightly more work than changing straight cut gears in a Quick Change, and those extra gears in a Quick change add friction drag, perhaps 2 to 4%.
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Re: How much does rear gear ratio effect HWY gas mileage?
[Re: HotRodDave]
#2515310
06/30/18 03:17 PM
06/30/18 03:17 PM
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Joined: Jan 2004
Posts: 8,233 fredericksburg,va
cudaman1969
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master
Joined: Jan 2004
Posts: 8,233
fredericksburg,va
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my 2000 dodge van with a 5.9 and 3.92s is close to that fluctuation and it definately locks solid in lock up. It will not hold the speed as precise as my 2011 1500 ram did on the data stream on my scanner or in real life on the freeway running side by side.
I have a set of 3.21s to install, I am positive they will give me better highway MPG.
Interesting, my scanner would stay at 60 then going down a hill would creep to 61 but rpm would go down to 1888. All over the place. I'm thinking the converter is not locking up to well (all new parts, electrical and trans). Will the lockup fluctuate 100 rpm? I have a set of 3.54 for the Dana that I would like to try. Talked to the Dodge service man, he said no problem reflashing pcm for the ratio change. Dont waste money taking it to the dodge dealer for a "flash" after a ratio change, the vehicle speed is measured after the gears and will not affect anything computer related changing gears. Thanks, just removed the speed sensor connector on trans checking what you said, speedo still works! It does work off the rearend. 3.54s are going in today!
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Re: How much does rear gear ratio effect HWY gas mileage?
[Re: ragtop]
#2516056
07/01/18 09:14 PM
07/01/18 09:14 PM
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Joined: Jan 2004
Posts: 8,233 fredericksburg,va
cudaman1969
master
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master
Joined: Jan 2004
Posts: 8,233
fredericksburg,va
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Update, 3.54 gears are doing fine. Just floats along with very little pedal effort at 50-60 and mph is dead on. Used the state police mile lay off signs on the highway, cruise set at 60, I went 59.96 seconds so that's real close. Filled up today so in about 100 miles I'll check millage, feels like it will be better than 13.5 mpg, hope, hope. Van just feels all around much better, didn't lose any power that I could tell.
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Re: How much does rear gear ratio effect HWY gas mileage?
[Re: GoodysGotaCuda]
#2524878
07/21/18 07:03 AM
07/21/18 07:03 AM
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Joined: Jan 2003
Posts: 3,575 The Netherlands
BigBlockMopar
master
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master
Joined: Jan 2003
Posts: 3,575
The Netherlands
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Axle efficiencies come into play. The internals of the transmission [working through a fluid] driveshaft and axle gears [working through a fluid] have to spin at higher rates, consuming more energy. ...
Last week I did some very unscientific testing in my '73 Dart (360ci A518, 3.55:1 in a 8-3/4 rear axle). Tried to measure drivetrain losses with the help of the MegaSquirt ECU and TunerStudio. Proceded by raising the rear tires just of the ground, put transmission into Drive, throttle it a bit and let it upshift to 3rd and into OD. Then I let the engine 'idle' with the wheels spinning, making sure the trans stayed in 3rd+OD by looking at the speedometer. Then I checked the engine-load kPa with TunerStudio. Did the same with trans in neutral. Difference in load with transmission in Neutral and in OD was just 5 kPa (30kPa in N, 35kPA in OD). About 5 kPa drivetrain (transmission & rear axle) loss, at low rpms. Now I didn't test at higher speeds to see if the difference would be greater.
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Re: How much does rear gear ratio effect HWY gas mileage?
[Re: ragtop]
#2524914
07/21/18 11:27 AM
07/21/18 11:27 AM
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Joined: Sep 2007
Posts: 14,889 up yours
Supercuda
About to go away
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About to go away
Joined: Sep 2007
Posts: 14,889
up yours
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with such a small change in the numbers one wonders if any of that is voltage drop due to more load?
They say there are no such thing as a stupid question. They say there is always the exception that proves the rule. Don't be the exception.
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