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Old 03-02-2019, 01:26 PM   #1
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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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Old 03-02-2019, 01:46 PM   #2
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Without knowing the engine and transmission Iím going to say 3.92.
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Old 03-02-2019, 01:50 PM   #3
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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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Old 03-02-2019, 01:52 PM   #4
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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.

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Old 03-02-2019, 01:58 PM   #5
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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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Old 03-02-2019, 02:03 PM   #6
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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.

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Old 03-02-2019, 02:17 PM   #7
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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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Old 03-02-2019, 02:42 PM   #8
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Old 03-02-2019, 03:14 PM   #9
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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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Old 03-02-2019, 03:29 PM   #10
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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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Old 03-02-2019, 03:52 PM   #11
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Thanks, that's what I was wondering about. Engine would be a 5.7L v8 gas.
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Old 03-02-2019, 03:53 PM   #12
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Great rule of thumb.... thanks.
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Old 03-02-2019, 03:56 PM   #13
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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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Old 03-02-2019, 04:51 PM   #14
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Quote:
Originally Posted by Btsanders101 View Post
Thanks, that's what I was wondering about. Engine would be a 5.7L v8 gas.
It also will help if you posted how speeds the transmission has.
Makes a difference in rear end ratio.
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Old 03-02-2019, 08:02 PM   #15
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Quote:
Originally Posted by Btsanders101 View Post
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?
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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Old 03-02-2019, 08:16 PM   #16
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With the choices given 3.92 without a doubt
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Old 03-02-2019, 08:24 PM   #17
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Originally Posted by My17Ram View Post
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.
Where do you do your towing?
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Old 03-02-2019, 08:31 PM   #18
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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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Old 03-02-2019, 08:33 PM   #19
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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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Old 03-02-2019, 08:36 PM   #20
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Please post the available transmission gear ratios, along with axle ratios and tire sizes. We can help from there.
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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