3.55 vs. 3.92 - MPG vs. Towing Ability - Page 2 - Ram 1500 Diesel Forum
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post #11 of 23 Old 08-24-2014, 09:05 AM
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Originally Posted by Katoom250SX View Post
Oh boy....you are right on the bubble. Technically you would be over those few times a year, but I'm sure the 3.55s would work. Really with that weight I'd be more concerned with suspension sag. I'm not towing heavy, but for the price I've already purchased a set of air lift air bags. They are supposed to be good for a 1000 lbs. They help with sag, bounce, and some say sway. I've never used em but for under 100 bucks I figured it would be a nice add on. I'd like to hear someone chime in on difference in mpg. If it's minimal maybe 3.92s won't be a bad fit for you since you actually pull something that's heavy. Do the math once. Figure 1 mpg less over say 50000 miles and see what the 3.92s would actually cost you. If it's not much it may be a good option for you.
Can't he just get factory air suspension?

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post #12 of 23 Old 08-24-2014, 09:55 AM
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If you live in a relatively level terrain & are towing that infrequently, I'd definitely go with 3.55 & add air suspension. The torque curve of the ed is a great match for 3.55's. I use mine primarily for long trips & love the sweet spot of peak torque falling at about 75mph. Fwiw I've had 1600# in the bed with 2 big guys, a full tank & a heavy (about 200#) bed cover and the air suspension leveled it out perfectly without a hiccup.
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post #13 of 23 Old 08-24-2014, 01:14 PM
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I think 3.92 is the way to go for sure.

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post #14 of 23 Old 08-24-2014, 01:20 PM
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Originally Posted by DIESELBLOCK View Post
Can't he just get factory air suspension?
Yes he absolutely could.....for a additional $ 1600.00. Or he could save $ 1520.00 & add a air lift kit as I am. And if he wanted an on board compressor for the kit it would only be 250 more. Don't get me wrong, I think the air suspension is cool, but it is the only option I elected to not get.
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post #15 of 23 Old 08-24-2014, 03:41 PM
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Originally Posted by Katoom250SX View Post
Yes he absolutely could.....for a additional $ 1600.00. Or he could save $ 1520.00 & add a air lift kit as I am. And if he wanted an on board compressor for the kit it would only be 250 more. Don't get me wrong, I think the air suspension is cool, but it is the only option I elected to not get.
cool, any pics of your setup?

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post #16 of 23 Old 08-24-2014, 09:33 PM
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Originally Posted by DIESELBLOCK View Post
cool, any pics of your setup?
Air lift 60818 is the kit. A web search will give you all of the specifics. I haven't taken delivery of my truck yet but I have the above listed kit sitting on my workbench ready for install. I do not have the on board compressor and don't plan to add it. In just a few minutes I can add or subtract air just the same as a tire. Msrp if I recall is around 135.00 but I've seen them under 80.00 with free shipping. Air lift is a very reputable company and the kit has a lifetime warranty!
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post #17 of 23 Old 08-25-2014, 12:03 PM
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It seems to me the final drive gear ratio is pretty unimportant when you consider the transmission has 8 gears to choose from.

And the tow rating difference is bogus as the only difference is you might be sitting in 5th gear towing 9k pounds with 3.55s instead of 6th gear with 3.92s. It's marketing nonsense more than anything.
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post #18 of 23 Old 08-28-2014, 11:16 PM
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3.92 all day long

Grab the 3.92, you won't notice a difference in fuel economy unless your going over 50mph but you will have the higher tow rating and a bit more power to the ground. About 200rpm higher cruising at highway speeds....

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post #19 of 23 Old 04-08-2015, 01:35 PM
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3.55 vs 3.92

I went through this same process, prior to ordering and receiving my 2015 outdoorsman. I ultimately decided on the 3.55, as I sometimes tow, but sometimes do not, and desired the lower rpm's at highway speed with the 3.55.
With the tow/haul engaged on the transmission, it is really good at keeping you in a good rpm when towing. If towing a heavy trailer, it may just keep in 7th gear. Plus, and I did not realize this until actually driving and towing with the truck, you can downshift the transmission with a button on the steering wheel. It will stay there in that lower gear. That is, if you are towing heavy at 55 or 60 mph, you can just keep in a lower gear. The transmission is excellent and very flexible.
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post #20 of 23 Old 04-08-2015, 03:11 PM
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I have 355's have towed 14,000#'s on 21' trailer several times never had problem
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