3.21 2wd 5.7 qc swap to 3.55

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RamAz

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I have a 2017 qc 5.7 a8 that’s 2wd, I notice there isn’t a tow chart that has the tow capacity for a quad cab 4x2 5.7 with the 8 speed and 3.55 gears. Only the 6speed has 3.55 gears or a V6. Is there a reason? I want to go to bigger gears but right now I’m getting about 26 miles to the gallon going to phx and back which is about a 390 mile trip for me. (Still having about a quarter tank or slightly more left) I understand I’m driving a V8 truck but that’s why I got rid of my Sierra was for that reason. I was getting about 12-15 mpg and traveling as much as I do, I was spending equal to my truck payment in gas each month. I love my ram and I haven’t towed anything yet but I know I will have to when the day I move comes. 3.92’s wouldn’t be over kill obviously but would make driving my truck a drain on the wallet. So any advice?


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VernDiesel

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Tow with the 3.21s first. You might find the 8 speed is so much better than the trans it replaced that it still does an admiral job. If not skip the 3.55 & jump to the 3.92. If it’s insufficient with the 8 speed you need a bigger truck not a steeper gear.
 

69GWC

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Shoot my truck tows my 28' camper easy and it has 3:21s.
With that said gears always help and like was said I would go straight to 3:92s if I made the switch I would do 3:92s unless I got a great deal on 3:55s.
 

Pull Ya

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I agree with going to 3.92's if you change gears. I don't think that the hit on your mileage will be as great as you think. I have the 8 speed with the 3.92's and a bunch of bolt ons and with the crusie set I get about 22 mpg on the highway.
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mohemipar

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Yes, don't do all of that work for just 3.55's. Make it 3.92's if you think you need a lower gearing. Fuel economy should not be too big a difference between 3.21 and 3.92. You would probably have to go to 4.30 (maybe 4.10) and lower to really see any kind of significant hit on your highway MPG.
 

ExpressRules

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I could be wrong, but I think after 2014 RAM stopped offering the 5.7 1500 with the 3.55, only the 3.21 and 3.92. The 3.55 is still available with the 6.

I have the 3.55 in mine and happy with it.
 

Pull Ya

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IMHO changing from a 3.21 to a 3.55, the difference is almost insignificant. If you are going to invest in a gear change then to my way of thinking, going to the 3.92 would be more bang for your buck and you would see a greater difference.
Jay
 

14hemiexpress

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I also agree with every one else. If your going to do it go to 3.92 skip over the 3.55. I would honestly say 3.21 with the 8speed will be just fine. My truck is the 5spd 3.55 and it tows great. 1st and 2nd with the 8 speed are lower than 1st in the 5speed so it makes up alot.
 

jasonw

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I could be wrong, but I think after 2014 RAM stopped offering the 5.7 1500 with the 3.55, only the 3.21 and 3.92. The 3.55 is still available with the 6.

I have the 3.55 in mine and happy with it.

Pretty close. For 2013s, the you could get 3.21, 3.55, or 3.92 gears with the Hemi and 8 speed. Starting with 2014 model year, you could only get 3.21 or 3.92 with 8 speed/Hemi from the factory.

I love my 3.92s for the power, but they do hurt on the highway a bit. I'm pretty spirited of a driver though.

Don't take some supposed "mechanic" advice that you can install gears yourself if you've never done it before, BTW. Its not some simple "remove cover, remove old gears, insert new, replace cover" type of procedure as some claim. You need specialized tools to make fine adjustments. If you don't do it exactly right, you will destroy your gears, housing, and more, possibly while flying down the highway. No bueno.

Its more expensive, but I'd leave it to the professionals. And make sure it someone who has done Dodge/Ram gear installs before, if you decide to pull the trigger.

That all being said... I don't think you'd notice the difference, and would push you to the "not worth the money" line of thinking.
 
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RamAz

RamAz

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Thank you all, 3.92 it is.


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VernDiesel

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If you have towed heavy with the 3.21 let us know what you think after you have swapped & towed heavy with the 3.92. As to would you generally recommend it to others.
 
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