3.21 ---> 3.92 swap

[Kotta390]

Is there anything special about the differentials on the 13+ trucks with the differentials?

I keep seeing where people have the 8 spd trucks call the differential a 9.25ZF??


I got a set of 3.92s that came out of a 2007 Dodge Ram 1500.

Also I'm looking into getting an LSD, is the stock style ok? I love my 3.21s so far but I feel like I will love the acceleration of the 3.92s better and I am just trying to figure out ballpark pricing.

 

[sicmadek]

It wont work

 

[charonblk07]

You will need an aftermarket ZF carrier for the rear which you can then bolt the older gears into; the gears will not just bolt in between the Corporate 9.25 and the ZF 9.25. If it's a 4wd then you have to swap the front diff to a pre-'12 or get a front ZF diff with the 3.92s.

 

[Kotta390]

You will need an aftermarket ZF carrier for the rear which you can then bolt the older gears into; the gears will not just bolt in between the Corporate 9.25 and the ZF 9.25. If it's a 4wd then you have to swap the front diff to a pre-'12 or get a front ZF diff with the 3.92s.

So what are my options then? Is this going to be a dealer swap only or is there a company who sells the ZF gears and carrier?

 

[charonblk07]

So what are my options then? Is this going to be a dealer swap only or is there a company who sells the ZF gears and carrier?

Matt with Moe's has everything to do the 2wd ZF rear gear swap.

 

[Kotta390]

oh ok thanks!

 

[HammerHead]

If you got the 8 speed don't wast your money. All that $ doing that kind of swap you could have full bolt ons and spray.

 

[Kotta390]

If you got the 8 speed don't wast your money. All that $ doing that kind of swap you could have full bolt ons and spray.

Not looking to do bolt-ons or spray. Last time I checked a nice set of headers were more expensive than a gear swap. I am not talking about shorties either.

 

[CMil527]

As stated Matt will get you squared away if you wanna go this route just shoot him a message...good luck!

 

[sicmadek]

Not looking to do bolt-ons or spray. Last time I checked a nice set of headers were more expensive than a gear swap. I am not talking about shorties either.

Think again. A oem lsd is $600, zf3.92 is $400, fluid is $35 a quart, and install kit is $100. You can buy headers for cheaper than that but a decision has to be made about the piping after the headers.

 

[charonblk07]

Think again. A oem lsd is $600, zf3.92 is $400, fluid is $35 a quart, and install kit is $100. You can buy headers for cheaper than that but a decision has to be made about the piping after the headers.

Have you looked at a no-cat set of 1 3/4" ARH lately? They're $1,580 and $1,750 for catted; Stainless Works 1 7/8" w/ cats are $1,500 and 1 3/4" no cats are $1,400 . I'd say a gear swap is cheaper or at least a comparable cost and it should also be noted that a gear swap is a lot more 'seat of the pants' friendly than a set of headers. Install cost is about the same for either.

 

[sicmadek]

Have you looked at a no-cat set of 1 3/4" ARH lately? They're $1,580 and $1,750 for catted; Stainless Works 1 7/8" w/ cats are $1,500 and 1 3/4" no cats are $1,400 . I'd say a gear swap is cheaper or at least a comparable cost and it should also be noted that a gear swap is a lot more 'seat of the pants' friendly than a set of headers. Install cost is about the same for either.

JBA Stainless Longtube Headers 2006-2014 Dodge Ram 5.7 1500/2500/3500 2WD/4WD

I said decions need to be made about what to do with the rest of the exhaust

 

[HammerHead]

Not looking to do bolt-ons or spray. Last time I checked a nice set of headers were more expensive than a gear swap. I am not talking about shorties either.

Sorry bud, thought you had a 4x4. I would go 410 minimum, I went 355 open diff to LSD and 410's and love them. BUT, looking back I wish I went 456. Mechanic at the dealership almost talked me out of the 410's, told me my hwy RPM's would be 3000-3500RPM and my gas mileage would suck. Getting 18-19.6 hwy. one of my best mods to date.

 

[Kotta390]

Think again. A oem lsd is $600, zf3.92 is $400, fluid is $35 a quart, and install kit is $100. You can buy headers for cheaper than that but a decision has to be made about the piping after the headers.

The gears will give me much more bang for buck.

 

[Kotta390]

Sorry bud, thought you had a 4x4. I would go 410 minimum, I went 355 open diff to LSD and 410's and love them. BUT, looking back I wish I went 456. Mechanic at the dealership almost talked me out of the 410's, told me my hwy RPM's would be 3000-3500RPM and my gas mileage would suck. Getting 18-19.6 hwy. one of my best mods to date.

I have the 8spd, I feel like the 4.56s would be absolute overkill??

 

[sicmadek]

The gears will give me much more bang for buck.

I agree

 

[charonblk07]

I have the 8spd, I feel like the 4.56s would be absolute overkill??

If you have a 37" tire then the 4.56s would be worth it, but with the 4.417 1st gear you'll have a fun time in anything but dry weather trying to keep the tires from spinning. If it's a daily driver then the highest ratio I'd recommend is the 4.10, even with 35s. If you drag race it or tow then the 4.6 is a good option, otherwise go to the 4.10s if you want to keep any semblance of fuel economy.

 

[sicmadek]

Thad has 4.10s in his 8 spd with stock tires. He loves it and i think he only lost .5-1 mpg on the interstate.

 

[QwikKota]

A friend of mine with a Ram said that the new gear ratio has to be flashed into the PCM to avoid going in to limp mode. Any facts to that story?

 

[Hemi450hp]

That's false. Gear swaps are very easy on these trucks...nothing has to be done to the computer after the install.

And I am a big fan of the extra gear. I would go with the 4.10 myself. With us still offering the free install kit with the 4.10's, the cost is the exact same between the 2.