3.55 to 3.92 - is it worth it?

[fernandok]

Hey y'all.

I have a 2017 Ram 1500 with 3.55's.

I'm looking at doing a swap to 3.92's since I'm on 35's (would love 37's in the future as well) with the 6 spd trans.

Now this isn't a question about if it's worth it cost wise, I own a shop so doing the work is easy, along with having a lead on a front 3.92 differential assembly from a friends truck. So I'm just left with buying the rear 3.92 gear set and master install kit.

I really want 4.10's but that will require retrofitting an earlier diff into place.

What I want to know is WORTH it? Will I feel a difference?

I've regeared racecars and previous track cars, and it's noticable when you're WOT chasing cars around a track... but will I actually notice an increase in acceleration around town? Anyone who's had both sets of gears can possibly chime in?

 

[retired]

if paying for it no, but being it is so low cost and basically free labor I would do it.

 

[CheechDogg.0n37s]

If you are planning on going with 37s later on and you can do it then yes do it .... since it's not about money

 

[Zoe Saldana]

Hey y'all.

I have a 2017 Ram 1500 with 3.55's.

I'm looking at doing a swap to 3.92's since I'm on 35's (would love 37's in the future as well) with the 6 spd trans.

Now this isn't a question about if it's worth it cost wise, I own a shop so doing the work is easy, along with having a lead on a front 3.92 differential assembly from a friends truck. So I'm just left with buying the rear 3.92 gear set and master install kit.

I really want 4.10's but that will require retrofitting an earlier diff into place.

What I want to know is WORTH it? Will I feel a difference?

I've regeared racecars and previous track cars, and it's noticable when you're WOT chasing cars around a track... but will I actually notice an increase in acceleration around town? Anyone who's had both sets of gears can possibly chime in?

No.

Find a gear calculator on line that shows what happend with larger tires and gears.

 

[Burla]

You will feel a difference, but 3.92's wont be big enough to get those 37's moving like you want, and making room for larger gears isnt that big of deal if you really want 37's. So make up your mind, are you committed to 37's or is that a pipe dream? There are ways to get a little more performance without re-gearing when you are only talking about a smaller jump. Pedal Commander, tune shift points, beef up valve body, etc.

I dove my friends 3.92's when he was drinking at a giants game, I was very impressed with it over my 3.55's, I have a hard time breaking traction with my 3.55's, I had a hard time not breaking traction from a stop sign with the 3,92's, much more early power. You need to make a firm decision one way or the other, if you are firm on 3.92's, might want to stick to 35's, if you really want 37's, go all in. I will say, these front ends arent really friendly for 37 inch tires, you will have all kinds of wear issues and alignments coming. I say going to 3.92's and sticking with 35's is a good move.

 

[CheechDogg.0n37s]

If you are going to stick with the 35s then the 3.92s are enough to pull those 35s, you probably are "NOT" going to see a jump in acceleration because of the bigger tires over stock ...

If 37's is what you are wanting later on I wouldn't waste time and money to just jump to 3.92s though ... but if you "can" do it yourself a little something extra is better than nothing ....

 

[CheechDogg.0n37s]

I have 4.88s to be able to manhandle the 37s on my 1500 and I love it, I wouldn't even think of having anything but the 4.88s for 37s

 

[Zoe Saldana]

Gear Ratio and Tire Size Chart

How do you know what RPM to run if you want more power? Better towing? Better fuel efficiency. Find all the answers in this comprehensive gear ratio and tire size chart.

auto.howstuffworks.com

 

[crazykid1994]

Being that you have the 6 speed I think anything less than 4.10 is not enough. Honestly I would jump straight to 4.56 with the 6 speed if you really want to make a difference. Especially if you have plans to do 37s in the future.

 

[Lyle Longboat]

I grabbed 456 front and rear gears for my 37s from 3:55. Dog those 3:55 compared to the 456. I break loose with 37s or 35s on. I enjoy the 35s, however no - offset with the 24” rims and have to use spacers which is a downside. 20” rims with the 37s have a -51 offset which I’m running right now.

 

[67 StingrayJ]

I would have to say that amount of gear reduction isn't worth the cost. HOWEVER, if your willing to go to something a bit more drastic like a 4.56, I'd say pull the trigger.

I'm running 33"s with the 3.55 gearing. It still sucks the gas down so I figure why not go taller.

My questions is, is this something that a reasonably skilled man can do on his own over the weekend? I have 4x4 mind you...

 

[67 StingrayJ]

I grabbed 456 front and rear gears for my 37s from 3:55. Dog those 3:55 compared to the 456. I break loose with 37s or 35s on. I enjoy the 35s, however no - offset with the 24” rims and have to use spacers which is a downside. 20” rims with the 37s have a -51 offset which I’m running right now.

Did you do the gear swap yourself?
if so, where did you purchase the set?
How difficult was it?
Do you have pics?

 

[CheechDogg.0n37s]

Lol .. I was driving in the rain on Tuesday out here and shooting out the gates to make a left turn I broke it loose unexpectedly really ....

But yes, 4.56s with 35s and 4.88s for 37s is what I would recommend personally ... although the homie @the_goodguy07 3.21s with 35s and he daily drives it and hasn't complained about it ...

 

[RLJ10X]

I don't know about the 8 speed, but.....

If your buddy is on 35s, with the 5/6 speed and 3.21s, let me assure you, it SUCKS! Hard on the transmission to boot.

3.55s on 33s, with the 5/6 was horrible. I hated it

Kudos to your buddy. That combo would be way unacceptable for me.

 

[CheechDogg.0n37s]

I don't know about the 8 speed, but.....

If your buddy is on 35s, with the 5/6 speed and 3.21s, let me assure you, it SUCKS! Hard on the transmission to boot.

3.55s on 33s, with the 5/6 was horrible. I hated it

Kudos to your buddy. That combo would be way unacceptable for me.

He has the 3.21s with the 8 speed, daily drives it about 30 miles daily, flat highways really .... but he is wanting to regear now because he might go up to 37s himself too now lol ....

 

[WY-Dave]

No.

Find a gear calculator on line that shows what happend with larger tires and gears.

This is 1 of 2 that I used when I had our Jeeps. What this does is put your back to square one with the "effective" ratio (tire size plus diff gears)

Tire Size Change Calculator

The last year model suburban available with a manual transmission.

www.4lo.com

For example 33s with 3:55. I don't know what the popular gear choices are for the Rams (gave it up when I traded the Jeeps in)


for 37s


second calc https://www.crawlpedia.com/rpm_gear_calculator.htm
gears effect on engine speed. I don't know what the 8th gearing is, but a lil research and you can figure it out.




The 3.92s will raise the rpms (1:1) a whole 97rpms!!!
Now if you just put tires on

A loss of 134rpms. I don't know if this would be enough to change the trans shifting pattern.
But of course it can be taken care of with AlphaOBD or similar method

and for S&Gs just throwing on 37s


My quick backstory. Jeep came in 32s & 3.21. On the rolling hill here it would drop out of 6th on a easy uphill. I got my t35s and had to wait 2 weeks to get the gears installed. IT WAS HELL! it would barely stay in 6th even on flats. When I went 4.56, it was perfect. On the hills it wouldn't even bat an eye. I could even pull our 1900# popup without dropping a gear.

When I did the first calc with stock vs 35s, it told me to do 4.10s. I wanted a lil more umph and stepped it up to next step of 4.56s.


Now back to our regular programming,
Looking at the top first calc, it appears that 3.73 would be for 35s and 3.92 would be good for 37s to be back to square one in reference to the effective ratio.
35 with 35s will give you a lil more umph, but I don't seeing it be anything drastic.

 

[dhay13]

^ keep in mind that those 'charts' only determine the mechanical gear ratios but don't take into account the extra weight of bigger heavier tires. Rotating mass is much worse than static weight so adding 100lbs is like adding adding 500lbs of bumpers (just guessing at those numbers but you get the point)

 

[chopperman1]

Don't forget the front differential. Needs to change too.

 

[dhay13]

and re-calibrate the speedometer

 

[WY-Dave]

^ keep in mind that those 'charts' only determine the mechanical gear ratios but don't take into account the extra weight of bigger heavier tires. Rotating mass is much worse than static weight so adding 100lbs is like adding adding 500lbs of bumpers (just guessing at those numbers but you get the point)

Yup, forgot to mention that. @230am I was lucky to remember the calcs haha.