swapping out 3:90 gear to 3:21

porkchopssteelers · May 28, 2015

has anybody swapped the rear gear on a 1500, 5.7 ? I have a 2015 , 5.7 and although I like the off the line power with the 3:90 gear, I was thinking of swapping out to a 3:21 and was wondering if anybody had done something like this and how it affected the mileage

Csanders1992 · May 28, 2015

What kind of driving do you do? And how many miles you drive?

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SlowRoller · May 29, 2015

this type of question would receive more responses if it was moved from 'Site News' to the 4th Gen area.

xrsman · Jun 1, 2015

You'll spend a few thousand dollars doing this swap and you'll NEVER see any money back. You'll pick up 1 mpg maybe even 2 if you're really lucky. You'll give up a couple thousand pounds towing and a good bit of off the line snap.

Just to put it in perspective, the ecodiesel engine would take 100,000 kms to pay for itself and it will get 8 mpg better than the hemi. (if you baby the hemi)

It's not worth the swap! If you want to see a bit better mileage you should put a cold air intake, free flowing exhaust, and tuner on. Tuners should be out sometime this year for your truck. This will give you the same gain in mpg but will cost you a lot less.

CMil527 · Jun 1, 2015

more aggravation and $$ than its worth... I would leave it alone!

cptwing · Jun 1, 2015

Odd usually most folks on here would be trying to upgrade the 3:21 to 3:92.

bodyman247 · Jun 1, 2015

agreed ^

Zeak · Jun 2, 2015

Find someone wanting to go from 3.21 to 3.92 and swap axles.

Hemi_Express2013 · Jun 2, 2015

porkchopssteelers said:
has anybody swapped the rear gear on a 1500, 5.7 ? I have a 2015 , 5.7 and although I like the off the line power with the 3:90 gear, I was thinking of swapping out to a 3:21 and was wondering if anybody had done something like this and how it affected the mileage

Shouldn't be too expensive. I would check with your local dealer for gear pricing. Even with the 3.21, the 8 speed has more snap then 3.92 6 speed

bigolayne · Jun 2, 2015

I would love to swap out. I have a 2015 with 2500 miles on it and 3.21 wanting to go up...

clh1220 · Jun 2, 2015

Hemi_Express2013 said:
Shouldn't be too expensive. I would check with your local dealer for gear pricing. Even with the 3.21, the 8 speed has more snap then 3.92 6 speed

I Don't know what you call not too expensive. If it's 4wd going to be some where around 2 k. He would never recoup the money for that with mpg.

bigolayne · Jun 4, 2015

That's why I would love to swap axles. Let's meet up and get this done...

swapping out 3:90 gear to 3:21

porkchopssteelers

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Csanders1992

Senior Member

SlowRoller

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xrsman

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CMil527

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cptwing

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bodyman247

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Zeak

Senior Member

Hemi_Express2013

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bigolayne

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clh1220

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bigolayne

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