3.92 Gear upgrade from 3.21s

[sbuko213]

So the other day I found I've got the 3.21's on my truck, and since I'm putting larger tires on and planning on a bit of off-road with it, I'm considering upping it to 3.92s (I have the 8-Speed). How much does something like that cost?

 

[AzRamLover]

You have a 4x4, too. I haven't really looked into this so I can only repeat what the dealer told me when I bought my truck - like $2500.

 

[sbuko213]

****. Do they at least make LSD's for the 3.21's

 

[RLJ10X]

Sb, all is not lost.

Try that bad boy in 4 low. I'll bet you'll have all the off road mechanical advantage you can use, even with 35s. The super low 1st gear in the 8 is your friend.

While, it a poor substitute for a limited slip, the "Brake Lock",< that is what Jeep calls it, Does a passable job off road.

The "Street Slicks" are your biggest hold back, besides the sheer girth of these monsters.

The most fun you can possibly have Off Road is in an old used Cherokee, one of the little ones. Throw a set of aggressive tires on that little guy and it's very surprising where they'll go, and you don't have to worry about scratching it up.

 

[sbuko213]

Sb, all is not lost.

Try that bad boy in 4 low. I'll bet you'll have all the off road mechanical advantage you can use, even with 35s. The super low 1st gear in the 8 is your friend.

While, it a poor substitute for a limited slip, the "Brake Lock",< that is what Jeep calls it, Does a passable job off road.

The "Street Slicks" are your biggest hold back, besides the sheer girth of these monsters.

The most fun you can possibly have Off Road is in an old used Cherokee, one of the little ones. Throw a set of aggressive tires on that little guy and it's very surprising where they'll go, and you don't have to worry about scratching it up.

Ahh good insight. Eventually I'm gonna get an XJ project anyways, but I'm going about turning this into a desert truck, not full blown ramrunner, but plenty capable in the desert. 35" Red letters are going on it and I didn't want the added weight of those to hold it back at all.

 

[14RAM4X4]

I also have an 8spd and 3.21s. I went up to 295/60r20 Nitto TerraGrapplers and I really did notice the difference in performance... and mpg. I've looked into the 3.92s and here's what I've found:

Used 2013-2014 front diff = $500 - $700
Rebuilt 2013 front diff = $1500 From Just Differentials.com
Rear gears with install = $900 gears/install kit/ labor

So about $1600 - $2500. labor prices in your area can make a big difference too.

 

[AzRamLover]

Yes they do. The OEM and Auburn.

The OEM LSD ("anti-slip differential") is pretty decent, even with the 3.21s.

It's never gonna compete with Mitsubishi's S-AWC but it's a ton better than an open diff and S-AWC does rallying (as opposed to off roading).

 

[RLJ10X]

My tires are real close to stock, and I have a Hemi Fever tune. I think that might be part of the reason that my truck does pretty well on gas, if I try.

My nephew bought a 1990 Jeep Cherokee Lorado(?) last August for $500. It has the 4.0. What a great engine that is! He tossed the car tires and got a set of Hankook Dyna Pros. It's bone stock. It is surprising what that thing will do, and where it will go. Its been a blast!

 

[sbuko213]

I also have an 8spd and 3.21s. I went up to 295/60r20 Nitto TerraGrapplers and I really did notice the difference in performance... and mpg. I've looked into the 3.92s and here's what I've found:

Used 2013-2014 front diff = $500 - $700
Rebuilt 2013 front diff = $1500 From Just Differentials.com
Rear gears with install = $900 gears/install kit/ labor

So about $1600 - $2500. labor prices in your area can make a big difference too.

Gotcha. What was the drop in mpg? I'm getting 35x12.5 Red Letter Grabbers

 

[14RAM4X4]

Gotcha. What was the drop in mpg? I'm getting 35x12.5 Red Letter Grabbers

About 2-3 mpg. I was hitting 17-19 daily driving with about 80% city and 20% hwy. Now I'm pretty constant between 14.6 - 15.2 mpg. I got up to 16.2 mpg driving 90 miles round trip all hwy.

I'm sure it's a little higher due to taller tire size but I need to save up for a tuner to correct for it.

 

[sbuko213]

About 2-3 mpg. I was hitting 17-19 daily driving with about 80% city and 20% hwy. Now I'm pretty constant between 14.6 - 15.2 mpg. I got up to 16.2 mpg driving 90 miles round trip all hwy.

I'm sure it's a little higher due to taller tire size but I need to save up for a tuner to correct for it.

I already have the tuner so that may help me a bit there. I think that's where my friend was on his 3rd gen after he did the tuner and intake with 35x12.5 trail grapplers.