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Anyone convert a 3.21 to 3.92?

jtPNW

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I'm towing a 7k lb trailer and could use some extra gears. It pulls ok just hits 5k rpm going through 1-4. Rarely gets past 5th gear on hwy.

Any idea on cost and complexity to change gearing? All of my local dealers have never done it and won't quote it. :(
 
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Rob5589

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The rear is a piece of cake. The front is the issue. When I recently spoke to the shop I used to be associated with, they had not seen one nor had any specs on the front. They said it was all new for the 2019. They didn't even have a designation/name for it.
 

Jghallis

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The rear is a piece of cake. The front is the issue. When I recently spoke to the shop I used to be associated with, they had not seen one nor had any specs on the front. They said it was all new for the 2019. They didn't even have a designation/name for it.
Rob can you please elaborate on this? So down the road, if we wanted to change the rearend to 3.55 or 3.92 there is more involved than just changing the rear end? Wish I knew more about this kind of stuff ...
 
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Rob5589

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Rob can you please elaborate on this? So down the road, if we wanted to change the rearend to 3.55 or 3.92 there is more involved than just changing the rear end? Wish I knew more about this kind of stuff ...
Yes, if four wheel drive, you need to swap the gears in front as well.
 
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Rob5589

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Haha, yeah, it ain't cheap. Most shops get 400-600 per end plus parts. You're usually looking at 1400-1800 for a full gear swap, depending on parts needed. But again, that new front differential is a hold up for now.
 

Firebird

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Are you 2wd or 4wd? 2wd is simple, 4wd has the front gears welded in and you have to obtain a front end from a doner truck.
 
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Rob5589

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Are you 2wd or 4wd? 2wd is simple, 4wd has the front gears welded in and you have to obtain a front end from a doner truck.
Welded in, in what way? Never saw anything like that when I was in the biz but, that was a long time ago.
 

Firebird

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Welded in, in what way? Never saw anything like that when I was in the biz but, that was a long time ago.
I’m not sure how, but it’s only the 1500’s. Heavy duties are changeable
 

StuartV

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I'm towing a 7k lb trailer and could use some extra gears. It pulls ok just hits 5k rpm going through 1-4. Rarely gets past 5th gear on hwy.

Any idea on cost and complexity to change gearing? All of my local dealers have never done it and won't quote it. :(

So, you would rather be at 5K RPMs in 6th gear, instead of 5K RPMs in 5th? Why?
 

StuartV

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more gears = better ability to stay in the power band when going up and down hills

Changing rear ends does not give you more gears. It just changes what gear you'll be in (on the highway). I.e. It just changes which gear would have you in the powerband at any given speed. Going from a 3.21 to a 3.92 is not going to help you on the highway. If the powerband is 5K, then changing from a 3.21 to a 3.92 just means you'll be in, say, 5th gear instead of 4th, to be in the powerband.

And, if you're going down the road at 60MPH, and the engine is right in its powerband, it doesn't matter one bit whether you're in 5th gear with a 3.92, or 4th gear with a 3.21. It's the overall gear ratio that matters.

Changing from a 3.21 to a 3.92 would only be helpful to you for taking off from a dead stop, when towing something heavy. That would let you get into the powerband at a lower speed (i.e. sooner after takeoff).
 

Chevytraitor

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Rob can you please elaborate on this? So down the road, if we wanted to change the rearend to 3.55 or 3.92 there is more involved than just changing the rear end? Wish I knew more about this kind of stuff ...
The front and the rear have to be the same ratio
 

vincent3000

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Hi guys. I'm new to this forum but I'm driving ram trucks for a while. I currently own a 2019 Laramie. the reason I'm particularly interested in that post is that I bought the truck with the 3,92 ration but the dealer gave me the 3,21 by mistake. I know... My question is: Is it technically possible to swap the differentials from another truck in stock on a 2019? Can they reset the computer so it works like this never happened? I realy need the tow capacity of the 3,92 and they wont take the truck back. They offered to swap the diffenrentials. They say its possible but my local dealer says its not. SO does anyone ever did it? Thanks so much for your experience on this topic.
 

silver billet

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Hi guys. I'm new to this forum but I'm driving ram trucks for a while. I currently own a 2019 Laramie. the reason I'm particularly interested in that post is that I bought the truck with the 3,92 ration but the dealer gave me the 3,21 by mistake. I know... My question is: Is it technically possible to swap the differentials from another truck in stock on a 2019? Can they reset the computer so it works like this never happened? I realy need the tow capacity of the 3,92 and they wont take the truck back. They offered to swap the diffenrentials. They say its possible but my local dealer says its not. SO does anyone ever did it? Thanks so much for your experience on this topic.

I believe it's been done (by a member on this forum who was selling their original stuff after the swap), but don't ask what it costs. If the dealer says they can do it for you and it's either free or you're ok with the quoted cost, then I wouldn't worry about it.
 

vincent3000

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I believe it's been done (by a member on this forum who was selling their original stuff after the swap), but don't ask what it costs. If the dealer says they can do it for you and it's either free or you're ok with the quoted cost, then I wouldn't worry about it.
I'm worried its going to void the waranty on the entire train system and if it does not work and they have to change the computer as well and void the warranty on the entire truck I'll end up with a Frenkeinstein 70K$ truck without warranty. The seller says its ok, my local dealer says its not, and fca says they dont recommend it but they wont comment on wether it is doable or not. Thats why I wish to read the comment of someone who has actualy done it.
Thanks for the input though.
 

NDanecker

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Changing rear ends does not give you more gears. It just changes what gear you'll be in (on the highway). I.e. It just changes which gear would have you in the powerband at any given speed. Going from a 3.21 to a 3.92 is not going to help you on the highway. If the powerband is 5K, then changing from a 3.21 to a 3.92 just means you'll be in, say, 5th gear instead of 4th, to be in the powerband.

And, if you're going down the road at 60MPH, and the engine is right in its powerband, it doesn't matter one bit whether you're in 5th gear with a 3.92, or 4th gear with a 3.21. It's the overall gear ratio that matters.

Changing from a 3.21 to a 3.92 would only be helpful to you for taking off from a dead stop, when towing something heavy. That would let you get into the powerband at a lower speed (i.e. sooner after takeoff).

Yes - you do get more gears. Sometimes it's easier to understand if you take it to an extreme. If you only had 3 gears you'd have to spin the motor way up to allow it to shift to the next gear and you'd be very low in RPM's when doing so. If you had 13 speeds you'd have more gears to shift allowing the motor to stay in the torque curve sweet spot. More gears is better. 3.92's are better for towing - period.

In addition you have more control while going down hill as it is a mechanical disadvantage for the truck to push the motor with 3.92's vs. 3.21.

Please know the facts before posting misinformation.

Thanks
 

NDanecker

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Welded in, in what way? Never saw anything like that when I was in the biz but, that was a long time ago.
The gear set in the front axle is friction welded to the carrier. You would need to replace the gears (obviously) and the carrier. Probably adds $400 - $500 to the cost.

Personally, I would sell the truck for one that is equipped better for towing if you tow near limits and/or frequently. If only a few times a year and not near the limits - keep 3.21 and deal with the negative side effects of having those gears.
 

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