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Discussion Starter #1
Hey guys please help me out here. I'm trying to buy, well find and buy a 2013 ram 1500 sport 4x4 fully loaded with 3.92 gearing with low miles.
I haven't found one yet!! They are impossible to find. So my question is....
Is it practical to buy a 3.21 and pay to have the 3.92s put in??

I got a quite from the dealer ($4150)!!!!
I think I've seen people were swapping for a lot less. Can someone help me out with some info so I can jump on a ram I actually did find completely loaded missing sunroof, hood and has 3.21

I can't afford new so this is the closest I've seen so far to what I'm looking for
 

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What purpose do you feel you need the 3.92 ratio vs. the 3.21? Only reason I ask is because I have a 2013 Ram 1500 Sport 4x4 with the 3.21 rear end and I love it. I even have a 6" lift and 35" tires and I don't have any problems or complaints with the gearing. Plus it is an 8 speed so the 1st gear is ridiculously low for torque ;)
 

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Discussion Starter #3
I like torque.
I enjoy having fast vs slow. I heard 3.21 gets worse city mpg because it has less torque compaired to the 3.92 which takes less effort to move the truck at take offs, stop n go driving.

I don't currently own anything that is to big to tow with the 3.21, I just rather have the quickest option possible.
 

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Well if you buy the used one with the 3.21's and pay $4k for the gear swap how close are you to the cost of a brand new one with 3.92's?
 

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If it has the eight speed I would say go ahead and buy it with the original gears, if you don't like it after the purchase you can still do the swap but like others said the 3.21 gears are fine, I have 3.21 and have no complaints or problems here either
 

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gears can change the feel of a truck big time, and if you do majority city drivin 3.92s will help, but you gotta think about how long itll pay off... add a tuner( especially a hemifever tune), exhaust, drop in filter, and itll run better than a 3.92 truck for way cheaper.

just my .02 if it comes down to it
 

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I suggest looking into it some more. I've read the exact opposite have the 3.21 having less torque than the 3.92 and I know from personal experience having ran a 3.92 against my own 3.21 I outran them from a dead stop to 70 even with a 6" lift and 35" tires.

3.21 with 8 speed:
1st gear has an extremely low ratio at 4.71:1; then 2nd is 3.14:1; 3rd is 2.10:1; 4th is 1.67:1; 5th is 1.29:1; and sixth is 1.00:1. There are two overdrives with 7th at 0.84:1 and 8th at 0.67:1. The Reverse gear is a strong 3.30:1

Just my own two cents...
 

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I have the 3.21 axle as well. My fuel mileage is being killed by the arctic conditions that we've been continuously stuck with for the last couple of months, not the axle. The 8 speed is usually in 3rd by the time I'm in the middle of the intersection, so gearing is not a problem.
 

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I have the 3.21 axle as well. My fuel mileage is being killed by the arctic conditions that we've been continuously stuck with for the last couple of months, not the axle. The 8 speed is usually in 3rd by the time I'm in the middle of the intersection, so gearing is not a problem.
This. Once it gets back to 60-70 degrees then my combined mileage will go back to 18-18.5 from 17
 

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Let me start off by saying no.. I don't have an 8 speed transmission but I do have experience with different rear axle ratios.

In my opinion I would prefer 3.92 in any setup simply because I have had 3.55 and 3.21 before.

With the 3.21 and 3.55 the truck is quick to change gears in order to accelerate or even just a moderate increase in pedal pressure. This isn't bad per say but annoying. When you just want to move up just a bit and you cross that threshold where the truck needs to change gear you get a lot more power than what you need for that situation. To much gear hunting I felt.

My truck that had 3.92 would hold the gear and accelerate just fine. I see this mainly when climbing the mountains. The 3.92 could hold a certain speed in a higher gear for MUCH longer than the 3.55/3.21.

I feel the 3.92 gears just put the RPM in a better place for delivering power. This in turn helps eliminate the gear hunting that I hate.

As far as MPG I saw about .5 MPG less with my 3.92 on the highway. I did see a hair better in the city. The difference while towing and climbing hills is what sells me on the 3.92.

Most say 3.21 is fine.. well that is because most haven't driven a 3.92 rear axle ratio truck.
 

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Discussion Starter #11
so does anyone have any info on the swap cost??
the dealer says $4150, theyre crazy...
what's the cost if I go elsewhere??
 

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I think the price they quoted you is for the complete rear-axle assembly... MSRP for the complete assembly is $4170

Gearsets should be about $500 and labour should be no more than another $500 to set it up properly.

I ordered the 3.92, but would say to try out the 3.21 behind the 8-speed for a while and then decide. Worst case, I'd estimate $1000 to change later.

** Edit... I just noticed you said 4x4... double what I said. **
 

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I had a 2012 6 speed 3.92. Traded it in for a 2014 8 speed 3.21. All I can say is the 2014 is alot nicer to drive. It's smoother thru the gears and is quicker off the start. :smiley_thumbs_up:
As far as mileage goes winter gas, cold temps and heavy on the skinny pedal are the reason mine is not as high as it could be.
Just my opinion
 

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Discussion Starter #14
I think the price they quoted you is for the complete rear-axle assembly... MSRP for the complete assembly is $4170

Gearsets should be about $500 and labour should be no more than another $500 to set it up properly.

I ordered the 3.92, but would say to try out the 3.21 behind the 8-speed for a while and then decide. Worst case, I'd estimate $1000 to change later.

** Edit... I just noticed you said 4x4... double what I said. **
Well they quoted me $1680 for front because they can only replace the whole axle and $900 for rear gears and $1570 labor.
$4150.
 

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Have you test driven an 8-speed with the 3.21?? You might be surprised how they feel under your right foot.

The gearing on the 8-speed is really different than the old trans. FDR in second gear on the old trans is like FDR in fourth with the new one.
 

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Discussion Starter #16 (Edited)
I have yet to try to drive it but its not about me... I want to know if I do buy it and want the different gearing that it would be an affordable option.
$4150 isn't ,,, maybe $2000 at the most... but I'd still like to be sure before I spend $37k on something I don't like
 

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Rule of thumb around me is 1000$ for a 2 wheel drive truck regear and 2000$ for a 4 wheel drive regear.

Screw the dealership your getting ripped off at 4k. I don't know why people even consider them as an option unless for warranty work- they wanted 250$ when I called them this morning to find out why my air bag light was on...got a good laugh though.
 

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I have yet to try to drive it but its not about me... I want to know if I do buy it and want the different gearing that it would be an affordable option.
$4150 isn't ,,, maybe $2000 at the most... but I'd still like to be sure before I spend $37k on something I don't like
If you have $37K to spend... you're in new truck territory! :)

You might be surprised what you can buy these days.
 

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$4150 is high but not by much. These new ZF rear ends are not as simple to swap as the previous gearsets were. Everything I've read has said it would be about $3000 to swap. Well over $2k for sure.

Go drive both. You can sit here and have us tell you our opinions of each choice, but the one that matters is your opinion.

Here's mine: final drive ratio is what matters as opposed to the diff gear ratio, and the 3.21 8 speed has a much lower first gear FDR than a 6 speed 3.92. In fact it is a greater difference than the difference between the 3.92 and 3.21 in trucks with the 6 speed. The 8 speed 3.92 is even lower, but in my opinion it kind of makes 1st gear useless. You may feel different about it and enjoy shifting into 2nd at under 5MPH, so take it for what its worth.
 
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