Selecting a gear....or not

[theblackduck87]

Hi guys. Getting ready to swap out my factory open differential to the Eaton torsen style.
Was thinking of upgrading the gears while I was at it.
Mine is stock with 3:55 and was thinking of moving up to a 3:90.
It doesn't seem like a big change on paper but I'm sure there going to be more to it than just numbers.
Looking for thoughts and opinions on "To Change or Not to Change, That is the Question"

So What do Y'all think?

 

[NJMOPAR]

If you have 4wd you'll have to change both if you're going to a different ratio.
3:55 is plenty for launching and better highway mpg.

 

[theblackduck87]

If you have 4wd you'll have to change both if you're going to a different ratio.
3:55 is plenty for launching and better highway mpg.

It's a RWD. I don't know if I'd even bother at 2 for twice the price.=-)

 

[kurek]

Going from 3.55 to 3.92 is going to deliver just over 10% more torque to the ground in any given transmission gear, and will make the engine spin the same % faster at the same speed in the same transmission gear.

So if you're sitting at 1500rpm at 65mph now (example) you would be sitting at 1650rpm with the 3.92 gears.

Won't make a big difference in mpg really, unless you forget to also calibrate your truck for the new gears.

Since you're already doing the most expensive part the gears themselves should be relatively cheap. Treat yo self.

 

[theblackduck87]

Let me also clarify that the stock set runs at 2000 RPM in 4th gear at 55MPH. A set of 3:90 would only increase RPM by 200 and 4:10s would increase it by 300 calculated out on a 1:1 final drive (4th gear on mine)
I've pretty much made up my mind. Just curious to hear some opinions.

 

[Fast69Mopar]

Hi guys. Getting ready to swap out my factory open differential to the Eaton torsen style.
Was thinking of upgrading the gears while I was at it.
Mine is stock with 3:55 and was thinking of moving up to a 3:90.
It doesn't seem like a big change on paper but I'm sure there going to be more to it than just numbers.
Looking for thoughts and opinions on "To Change or Not to Change, That is the Question"

So What do Y'all think?

If you are opening the diff up then you might as well put in the gears that you really want. Depending on what you do with the truck is how I would decide on a ratio.

With my experience with the 45/545/65RFE trucks, the 4.56 gear is the best ratio for our trucks. The lower ratio really helps get these heavy trucks moving with only a 3.00 1st gear in the transmission. Cruise rpm is still relatively low so you can still hit the interstate in 5th gear without a problem.

 

[caulk04]

Once upon a time I had a dakota with the same trans you have. Went from 3.55 to 4.56 and loved it. Ran a ~32" tire. I'm sure I'd have also been happy with a 4.10, to be honest.

You seem to understand the % value of swapping gears, so I think you can make up your own mind. The main concern is can you live with the cruising RPM.

My opinion is to go big or don't do it.

 

[RLJ10X]

I'm a huge fan of my 4.10s. I don't see any point in 3.92s in a gear swap. Factory ratio:Yes!

I've never driven anything with 4.56s. Those may be even better than my beloved 4.10s

 

[CheechDogg.0n37s]

Hi guys. Getting ready to swap out my factory open differential to the Eaton torsen style.
Was thinking of upgrading the gears while I was at it.
Mine is stock with 3:55 and was thinking of moving up to a 3:90.
It doesn't seem like a big change on paper but I'm sure there going to be more to it than just numbers.
Looking for thoughts and opinions on "To Change or Not to Change, That is the Question"

So What do Y'all think?

What size tires are you planning on going with ? ... If you are going with 35s go with the 4.56s and 37s go with the 4.88s .... and since its only a 2wd you will have no problem getting the 4.88s for 37s .... one reason I got a 2wd lol ....

 

[CheechDogg.0n37s]

I'm a huge fan of my 4.10s. I don't see any point in 3.92s in a gear swap. Factory ratio:Yes!

I've never driven anything with 4.56s. Those may be even better than my beloved 4.10s

Oh man they are lol .... before I regeared my 2wd I drove a couple of trucks with 4.56s, 4.10s, and 4.88s .... being that I had 37s the 4.88s was a no brainer after driving the 4.56s with 35s lol ...

 

[15 Handicap]

Hi guys. Getting ready to swap out my factory open differential to the Eaton torsen style.
Was thinking of upgrading the gears while I was at it.
Mine is stock with 3:55 and was thinking of moving up to a 3:90.
It doesn't seem like a big change on paper but I'm sure there going to be more to it than just numbers.
Looking for thoughts and opinions on "To Change or Not to Change, That is the Question"

So What do Y'all think?

How much you want for the 3:55 gears?

 

[theblackduck87]

How much you want for the 3:55 gears?

Wow I haven't even done the swap yet. lol
and why would you want gears with 90K on them?

 

[15 Handicap]

Didn't realize that is what's on the clock.