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Old 05-10-2015, 08:17 PM   #1
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Gear Ratios

Hey Forest River Techs,

Just wondering if anyone can give me a simple (if there is one) explanation of gear ratios for trucks. I know it affects towing capability. When looking for Tow Vehicles should I be looking for higher / lower numbers... and how much difference does it really make?


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Old 05-10-2015, 08:22 PM   #2
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Higher gear ratio for towing.
Ie: instead of a 323 gear a 370 would be better.

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Old 05-10-2015, 08:27 PM   #3
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Bottom line, the bigger the number the lower the gear and the better for towing and worse for fuel mileage. A 4.10 is better for towing than a 3.23 or 3.70.
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Old 05-10-2015, 08:46 PM   #4
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Ahh... ok... is there usually a price difference? and... how much difference would it make... say on a regular 1500 / 150 series pickup? A few hundred pounds or very significant... a couple of thousand?


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Old 05-10-2015, 08:56 PM   #5
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Ahh... ok... is there usually a price difference? and... how much difference would it make... say on a regular 1500 / 150 series pickup? A few hundred pounds or very significant... a couple of thousand?
per
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The lower gear will increase your towing capacity but not your load capacity.
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Old 05-10-2015, 09:00 PM   #6
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There is a big difference. With my 2013 ram 1500 the 3.21 is around 7000lbs, the 3.55 is around 8600 and the 3.92 is around 10000. The price difference is not that much.
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Old 05-10-2015, 09:14 PM   #7
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The lower gear will increase your towing capacity but not your load capacity.

... meaning 'payload' what you can carry in the back...


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Old 05-11-2015, 08:05 AM   #8
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Yes changing your gear ratio will change your GCWR (the total weight of the Tv and trailer added together) but it will not change your GVWR ( the maximum your truck can weigh).
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Old 05-11-2015, 09:01 AM   #9
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A higher number is a lower gear ratio...ie 4.10 are lower gears then 3.73. The lower gears reflect more pulling power from stop but worse milage from higher engine RPM....So I'm told.
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Old 05-11-2015, 09:22 AM   #10
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Which is "better" for towing is a little more complicated than is being made out here. The number is how many times the driveshaft has to turn over for the tires to make one complete revolution. The problem is that people attempt to directly tie that to engine performance, forgetting that there is another set of gears in play in the transmission. Back in the old 3 speed days when, to my knowledge, they all ran a 1:1 in drive- even with the old 4 speeds where 3rd was 1:1 and everyone's OD was very comparable- you could pretty much stick to the rule being presented here that lower is better. Not so much any more. For example- many Tundra owners think they've got one heck of a towing hoss on their hands because they have 4.30 gears. If you run the numbers, however, the overall drive ratio is almost identical to the new Ford trucks with the 3.73 gears because of the transmission ratios. Another thing to consider is where the torque curve of the engine lies. The lower an engine will produce torque, the higher the gear ratio can be (once again 3.55 is "higher" than 4.10) while still performing adequately. For example, the Ecoboost engine like I have produces torque much lower than a naturally aspirated vehicle. IMHO, there is absolutely no reason for anything over 3.73 gears in one- I personally think the 3.55's are low enough- and apparently Ford agrees as the 2015 models with the highest tow ratings have them. For a naturally aspirated V8, I would want 3.73's in a Ford ( I think Chevy too, but not real familiar with current offerings), 3.92 in the Dodge, or 4.30 in the Tundra for towing a heavy trailer. The new diesels have much higher gears than they did in the past as well- primarily because they have much more power and 6 speed trannies. The F250 6.7PSD now comes standard with 3.31's and can be upgraded to 3.55's. In 1997 you couldn't get any higher than 3.55 and everyone considered the 4.10's to be a must for towing heavy. Clear as mud now?
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