Gear Ratio

Witch · May 13, 2016

While looking into tuners the question has surfaced what is my gear ratio ?
After **** some research on line it was inconclusive.
so I got under the truck and looked for it. Turns out the ratio is 3.92 on my truck.

My question here is what would be a the best gear for my truck or is the gear I have just fine ? knowing a few things about it,

1. 5.7 Liter Hemi
2. 8 speed transmission
3. cold air intake
4. factory wye pipe 14" Magnaflow one in two out muffler with custom pipe no resonators
5. 6" lift if that has an impact ?
6. 37" x 12.5 tires , next tires will probably go to 13.5 "
7. (Near Future) Working on getting a SCT tuner and cracked PCM
8 Main use is Highway and beat around town , do not do any excess hauling or anything like that

I do not know what else would impact it

Any insight as always is appreciated

Thanks

CRam · May 13, 2016

I think 3.92s with the 8 speed is a good combo for your setup. If it were a 6 speed I would say at least 4.56. If you are still wanting more gear you will have to swap the front axle to a pre 2012 I believe. No one makes gears for our years and it is still possible that our gears are welded in. There are some rumors that they are not though.

TestPilot57 · May 13, 2016

The main thing that impacts gear ratio is tire diameter (width doesn't really matter).

3.92s with 37s is roughly equivalent to 3.50s with stock size tires, which is well within the typical stock overall ratio. I don't know the percentages, but would be willing to bet that the single largest stock ratio is 3.21 on 1500s.

That said, to get back to your stock feel, 4.56s would do it, with a slight boost.

What it all comes down to is, what matters to you? The lower (number) gear ratio will generally give you better mileage but less application of torque. The higher number will be the opposite. If you're pretty happy with the power you have, stick with the stock gears. A tuner will give you some more, and is a relatively cheap and very easy upgrade. Gears will be moderately expensive and not a project most people will do in their back yard.

Witch · May 13, 2016

Thansk guys,

Question, why would Ram ship my truck with a 3.92 gear when the stock tires were only 31"

I mean I am happy they did, just does not add up in my head though ? wouldn't the 3.21 be more appropriate with a 31" tire ?

TestPilot57 · May 13, 2016

I've never seen 31s on a stock Ram. 33" is normal AFAIK.

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LifeSTRONG · May 13, 2016

TestPilot57 said:
I've never seen 31s on a stock Ram. 33" is normal AFAIK.

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No my 17's were a 265/70/16=31, so they can come with 31's stock.

OUMX117 · May 13, 2016

LifeSTRONG said:
No my 17's were a 265/70/16=31, so they can come with 31's stock.

Based on his picture, he has a sport which came with 275/60/20 which are right at 33"

TestPilot57 · May 13, 2016

Hmmm. That's odd. I have a 17" spare which is also 33" so I (wrongly) assumed they all were the same. BTW 265/70/17 is technically 31.6", which would round to 32". But then again all sizes vary up to an inch compared to spec...

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Witch · May 13, 2016

No I have an Outdoorsman, came with 17"rims
it had 265/70R17 GY Wranglers

LifeSTRONG · May 13, 2016

My bad I meant to put 265/70/17

audio1der · May 13, 2016

8 spd. transmissions weren't introduced until 2013
You either have a 2013, or a 6sdp trans.
Either way, you have the best gearing for getting out of the hole fast and towing.

Witch · May 13, 2016

audio1der said:
8 spd. transmissions weren't introduced until 2013
You either have a 2013, or a 6sdp trans.
Either way, you have the best gearing for getting out of the hole fast and towing.

Yes I have a 2015 Ram 1500 Outdoorsman

All the charts i look at say the 3.92 is out of the range for 37's ?

TestPilot57 · May 13, 2016

First off, that combo is still in the yellow. BUT, it's obviously not referencing a modern tranny - stating "4th gear at 65 MPH"...!! An 8sp with 3.92 and 37s is very driveable. If you don't have enough power, jump to minimum of 4.56, or go as high as you can if you want the most power. It will be expensive. A supercharger might be a better way to go in that case.

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Witch · May 13, 2016

Thanks, I could not find any charts that address the modern Ram's

I am stoked that I can use the gear i have, Glad I looked under the truck.

I thought I had a 3.21 gear after reading some stuff on line about base models.
Truck must have an option on it that it came with the 3.92 gear ?

TestPilot57 · May 13, 2016

No, 3.92 is a line item option (best $75 you can spend!). At least on the mid to higher models with hemi.

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HemiPower36 · May 13, 2016

3.92 is good. Of course 4.56 is better. Will cost lots of $$$. At Least you didn't have 3.21.

Witch · May 13, 2016

Thanks for all the help, going to stay with the 3.92 gear and build it up HP with bolt on's

Hoping to get this SCT X4 this month

Gear Ratio

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