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03-02-2019, 01:26 PM
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#1
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Junior Member
Join Date: Jun 2017
Posts: 10
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Best Gear Ratio?
I am shopping for an upgraded tow vehicle. Three gear ratios are offered. 3.21, 3.55, and 3.92. I would be towing a 27' Forest River Surveyor. Do I need the 3.92 or is 3.55 OK?
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03-02-2019, 01:46 PM
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#2
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Senior Member
Join Date: Apr 2017
Posts: 158
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Without knowing the engine and transmission I’m going to say 3.92.
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03-02-2019, 01:50 PM
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#3
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Multi-Slacker
Join Date: Aug 2017
Location: SoCal
Posts: 2,279
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Assuming the engine can handle it, 3.55 might be OK on the flats while 3.92 (or higher) will be needed for western mountains. I have 4:10s in my 2500 Chevy.
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Safe Travels
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03-02-2019, 01:52 PM
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#4
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Senior Member
Join Date: Aug 2018
Location: Richmond VA
Posts: 4,558
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You going to be towing it every day? If not the ratio makes no difference.
3.73 axles on my '07 Ford 5.4V8 towed no better then the 3.31 axles on my '17 3.5EcoBoost. With a good engine torque curve the axle ratio matters little.
-- Chuck
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03-02-2019, 01:58 PM
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#5
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Recently new!
Join Date: Dec 2014
Location: Arizona, in The Land of Scorch!
Posts: 1,206
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Add to the confusion....GM and Ford are about to release new 10 speed transmissions to the heavier trucks. Do not know how many overdrive gears will be in them, so homework will have to be done what rear gear ratio will be best!
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1987 Starcraft Nova tent trailer, purch. '87, sold 8.14
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2001 Ford F-250 7.3
Loving wife, R.I.P., 6/6/19
and Mason the always dirty dog! R.I.P, 2/19
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03-02-2019, 02:03 PM
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#6
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Broken Toe
Join Date: Jan 2012
Location: Imperial (St. Louis) MO
Posts: 3,745
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As a general rule of thumb...
The only time you will regret having too short (numerically larger) of gears is at the fuel pump. You will regret too tall (numerically smaller) gears all the rest of the time.
Tim
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FROG Member MO-0008-571 Since 20124444444444My Project Blog: https://cowracer.blogspot.com/
"Camper" 2016 Rockwood Signature Ultralite 8329ss
"Casper" 2017 Ram 2500 Laramie Diesel
..ProPride 3P Hitch - "Yeah. It's worth it."
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03-02-2019, 02:17 PM
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#7
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Scoundrel
Join Date: Feb 2017
Location: Montrose, Colorado
Posts: 2,809
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For a Dodge Ram 1500 you'll likely get a higher towing capacity with a 3.92 rear axle.
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2015 F-150 5.0L V8 XLT Crew Cab, 4x4, Tow Package, 36 gal tank, 3.55 locker, 1891 payload, Integrated Brake Controller, Roadmaster Active Suspension
Wooden Spoon Survivor
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03-02-2019, 02:42 PM
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#8
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Senior Member
Join Date: Jul 2015
Posts: 7,053
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4.10:1 or nuthin’
But I don’t really know.
Bruce
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2016 Rockwood Windjammer 3029W Diamond Edition
2015 Chevy 3500HD LTZ 6.0 Crew Cab 4x4 Long Bed 4.10:1 SRW
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03-02-2019, 03:14 PM
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#9
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Senior Member
Join Date: Nov 2017
Location: Dayton Ohio
Posts: 3,598
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Check the towing capacities of the vehicle. Yours trailer could be #7,000.
Most new trucks have transmissions with more gears. Usually a lower first gear. Many automatic transmissions start the car in second as a result. My new Jaguar does.
Older trucks had a four speed with a non synchro granny low you used to pull for ultimate power and nothing else. Sort of the same deal.
The rear number a fixed gear ratio. The higher the poorer the mileage every day. A little faster. Runs at higher rpm on the highway.
If your pulling boats out of water go big. Otherwise I would go with the truck stats.
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03-02-2019, 03:29 PM
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#10
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Grammar Pedant
Join Date: Aug 2017
Location: Frederick, CO
Posts: 1,580
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Don't know the truck platform, engine, weight of the trailer, where he's towing, or anything else. So, I'm going with 8. My answer is 8.
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TV: 2019 F-350 Lariat 4WD CCSB 6.7 PSD 3.55, 3,591 lb payload
Former RV: 2018 Rockwood Mini Lite 2504S
Former RV: 2007 Fleetwood/Coleman Utah
Former TV: 2005 F-150 King Ranch 4WD SCrew 5.4L Tow Package
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03-02-2019, 03:52 PM
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#11
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Junior Member
Join Date: Jun 2017
Posts: 10
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Thanks, that's what I was wondering about. Engine would be a 5.7L v8 gas.
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03-02-2019, 03:53 PM
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#12
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Junior Member
Join Date: Jun 2017
Posts: 10
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Great rule of thumb.... thanks.
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03-02-2019, 03:56 PM
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#13
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Junior Member
Join Date: Jun 2017
Posts: 10
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I will not be towing everyday, but will eventually be touring the entire country, including mountains eventually...
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03-02-2019, 04:51 PM
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#14
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Site Team
Join Date: Jan 2007
Location: Goodyear, Arizona
Posts: 33,835
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Quote:
Originally Posted by Btsanders101
Thanks, that's what I was wondering about. Engine would be a 5.7L v8 gas.
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It also will help if you posted how speeds the transmission has.
Makes a difference in rear end ratio.
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Dan-Retired California Firefighter/EMT
Shawn-Musician/Entrepreneur/Wine Expert
and Zoe the Wonder Dog(R.I.P.) 
2016 PrimeTime TracerAIR 255, pushing a 2014 Ford F150 SCREW XTR 4x4 3.5 Ecoboost w/Max Tow Package
4pt Equal-i-zer WDH and 1828lbs of payload capacity
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03-02-2019, 08:02 PM
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#15
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Senior Member
Join Date: Nov 2017
Location: Northeast Ohio
Posts: 266
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Quote:
Originally Posted by Btsanders101
I am shopping for an upgraded tow vehicle. Three gear ratios are offered. 3.21, 3.55, and 3.92. I would be towing a 27' Forest River Surveyor. Do I need the 3.92 or is 3.55 OK?
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The ratios you reference and the 5.7L engine seem to indicate a Ram 1500. I don't know the weight of your trailer but at 27ft I would suggest getting the 3.92 ratio.
With that said I tow my 233s (about 5100lbs loaded) very well with my Ram 5.7 and 3.21 rear end ratio. My 2017 has the 8 speed automatic. I'll assume yours would too.
The 3.21 allows the truck 21+ mpg on the highway not towing, and effortless 80+ mph cruising. The key here is the 8 speed auto.
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03-02-2019, 08:16 PM
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#16
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Senior Member
Join Date: Feb 2019
Posts: 145
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With the choices given 3.92 without a doubt
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Chris
2020 Grand Design 337RLS
2019 Rockwood 2608BS (Sold)
2005 Rockwood 2516G (Sold)
2018 Chevy 2500 6.0 / 4.10's
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03-02-2019, 08:24 PM
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#17
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Multi-Slacker
Join Date: Aug 2017
Location: SoCal
Posts: 2,279
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Quote:
Originally Posted by My17Ram
The ratios you reference and the 5.7L engine seem to indicate a Ram 1500. I don't know the weight of your trailer but at 27ft I would suggest getting the 3.92 ratio.
With that said I tow my 233s (about 5100lbs loaded) very well with my Ram 5.7 and 3.21 rear end ratio. My 2017 has the 8 speed automatic. I'll assume yours would too.
The 3.21 allows the truck 21+ mpg on the highway not towing, and effortless 80+ mph cruising. The key here is the 8 speed auto.
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Where do you do your towing?
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Safe Travels
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03-02-2019, 08:31 PM
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#18
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Senior Member
Join Date: Apr 2016
Posts: 1,011
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Please post the available transmission gear ratios, along with axle ratios and tire sizes. We can help from there.
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03-02-2019, 08:33 PM
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#19
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Junior Member
Join Date: Jun 2017
Posts: 10
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Presently, just in the southeast. However, the purpose of the upgrade would be so we could handle steeper grades if needed... Right now I tow it with my 2.8L Chevy Colorado Diesel and it does well, including NC and VA mountain areas which I know are modest compared to the Rockies.
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03-02-2019, 08:36 PM
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#20
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Junior Member
Join Date: Jun 2017
Posts: 10
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Quote:
Originally Posted by Jay2504
Please post the available transmission gear ratios, along with axle ratios and tire sizes. We can help from there.
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I am looking at the 2019 RAM. Tires could be 18" standard or 20" as an upgrade. I'm not familiar with the transmission other than it's an 8 speed. Maybe the MFR specs can be found.
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