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02-18-2015, 10:24 AM
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#101
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Vintage Kin
Fort Worth
, Texas
Join Date: Nov 2006
Posts: 8,014
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Quote:
Originally Posted by SteveH
Picked up the truck yesterday afternoon and just drove it home. It seems at 60 or so in sixth gear it has only increased the RPM by 100, so should not make any major difference in highway fuel mileage. I did notice the gear change more at lower speeds in the lower transmission gears, which makes sense to me, and this should give me what I wanted..... more power at lower hill climbing speeds.
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I imagined you'd enjoy the change. Though it really makes no difference on what the truck can do outside of higher altitude driving. About the only reason I hesitate in changing mine is a consideration of changing my home to such a place.
There are gear ratio calculators online that will give exact change. If one likes to tow at 60-mph, the rpm will be clear as to the difference made by the ratio change. Worthwhile to see if the prediction is met.
The auto trans is essentially a 4+2 arrangement as I recall. Two overdrive gears. Or, why I wish my truck had a seventh gear: one OD for towing on the flats, and a second higher OD gear for running empty/solo.
What is your predicted 60-mph rpm and actual?
My 10k rated trailering & 13k GN/5er GCVWR is 20k with 3.73 gears and I run 60-mph right under 1,800-rpm when in Overdrive. I'll check the Direct rpm at 60-mph today as I can't remember the number.
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02-18-2015, 10:36 AM
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#102
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Rivet Master
1994 30' Excella
alexandria
, Kentucky
Join Date: Aug 2004
Posts: 2,321
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My truck has the 3:73 gears. I find that 65 - 68 mph on the interstate seems to be a good mph to tow that has the least amount of transmission shifting on the hills. You truck may do better since it has slightly more horsepower and much more torque than my 09.
__________________
Steve, Christy, Anna and Phoebe (Border Collie)
1994 Classic 30'11" Excella - rear twin
2009 Dodge 2500, 6 Speed Auto, CTD, Quad Cab, Short Bed
Hensley Arrow hitch with adjustable stinger
WBCCI # 3072
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02-18-2015, 12:01 PM
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#103
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Vintage Kin
Fort Worth
, Texas
Join Date: Nov 2006
Posts: 8,014
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In this 2004 305/555 CTD with six speed manual:
60 is a few hairs shy of 1,800-rpm in Overdrive.
And right under 2,400-rpm in Direct.
With that double OD in yours you can see why theoretically an auto trans truck otherwise the same could get better mpg on the highway. The manual trans in your year model is from a different supplier and has a longer OD gear. But still not as long as the 68 auto.
All this sums to different engine computer programming between auto and manual, but the change you've made shouldn't much affect it. I'd guess you've moved from one edge of the envelope to the other for an auto trans truck where 4.10 is not available. A half step versus a full step in change.
Fuel burn is just a way of looking to regen cycle frequency, etc.
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02-18-2015, 12:33 PM
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#104
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Rivet Master
2005 39' Land Yacht 390 XL 396
Common Sense
, Texas
Join Date: Sep 2007
Posts: 5,319
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At about 60 mine was turning 1600 yesterday. In the past, I've noticed the best fuel mileage on the highway at 1700-1800 RPM.
__________________
Regards,
Steve
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02-18-2015, 06:19 PM
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#105
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Rivet Master
2013 31' Classic
billings
, Montana
Join Date: Feb 2010
Posts: 3,577
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That is about right ,mine runs 60-65 at a1500-1600, speedo might be a little fast according to the garmin, I would like to try the 3.42 , I did have a 4.10 with a 7.3 and a 5 speed , 2200 running about 62 , not good. My model a had 4.11, and I changed it to 3.54, I like it better.
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02-19-2015, 04:11 PM
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#106
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3 Rivet Member
1991 29' Excella
Currently Looking...
Marco Island
, Florida
Join Date: Sep 2012
Posts: 164
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We just bought a 2015 Ford F-250 diesel long bed after having a Ford F-150 EcoBoost. My hubby thought it was pretty funny that shortly after our purchase I came home with the newest issue of "Diesel Power" Magazine. To your point this article talks about the mystery of to how to determine the Gross Combined Weight Rating (GCWR) of a vehicle and trailer combination. Apparently they are going to standardize this so you can shop and compare vehicle to vehicle. SAE J2807 Tow Tests - The Standard
Maybe I'll subscribe!
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02-20-2015, 02:56 AM
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#107
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New Member
Currently Looking...
Mount Pleasant
, Texas
Join Date: Dec 2014
Posts: 3
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The J2807 Towing Standards have been around since 2009 when they were agreed to by the auto manufacturers beginning with the 2013 model year; however there has been some "back pedaling" mainly by Ford.
http://www.autonews.com/article/2013...-isnt-standard
Bill
__________________
'03 Ram 3500 Q-Cab Dually, CTD, Auto Trans
Former Owner:
1976 Airstream 29'
1982 Airstream 31'
1987 Argosy 5th Wheel 31' with slideout
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02-20-2015, 07:05 AM
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#108
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Rivet Master
2005 39' Land Yacht 390 XL 396
Common Sense
, Texas
Join Date: Sep 2007
Posts: 5,319
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Quote:
Originally Posted by Retired Iron
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Not saying it's not true, but that article is dated February 11, 2013, or over two years ago.
It would be interesting to know for sure what all the manufacturers are doing today.
__________________
Regards,
Steve
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02-20-2015, 08:58 AM
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#109
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Rivet Master
Vintage Kin Owner
N/A
, N/A
Join Date: Sep 2012
Posts: 989
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I believe Ford/GM/Ram are J2807 compliant with the 2015 models. Toyota adopted the standard immediately. Nissan will be compliant with 2016 models.
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03-08-2015, 12:56 PM
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#110
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Rivet Master
2005 39' Land Yacht 390 XL 396
Common Sense
, Texas
Join Date: Sep 2007
Posts: 5,319
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OK, went to a rally this weekend of about 300 miles round trip, and if anyone is interested, the truck towed the trailer noticeably better with the 3.73 gears, but I won't say significantly better. Winds were not good for checking fuel mileage, but it looks to be about the same.
__________________
Regards,
Steve
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03-09-2015, 12:43 AM
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#111
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Rivet Master
2013 31' Classic
billings
, Montana
Join Date: Feb 2010
Posts: 3,577
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When ever one spends some monies on something ,that alone will make it better!
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