2019 Rear Gear Ratio swap

[ShamrockShooter]

Hi there. I am a Silverado owner looking at buying a new ram2019. I found just the one I want in a Laramie trim as a dealer demo. The only thing is it has the 3.92 elock rear axle. I drive mostly highway and my trailer is only 3500 lbs. MPG is a bigger priority for me.

Can you easily swap to 3.21 gears or am I better off just trying to find another truck?

Sorry if I posted this in the wrong spot.

Thanks

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[Luxy72462]

In all honesty these trucks aren’t spectacular on gas so you probably won’t see a noticeable difference between the 2 gears. There’s several threads on different combos and what guys are getting. I’d look at those topics before trying to swap gears.


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[Joeyp]

In all honesty these trucks aren’t spectacular on gas so you probably won’t see a noticeable difference between the 2 gears. There’s several threads on different combos and what guys are getting. I’d look at those topics before trying to swap gears.


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I dont think you should worry about it...I like the 3.92 better!

 

[NordicNevs]

Moes performance has an OEM 4:10 ratio for sale. That would be interesting.

They also have a 3:55 and OEM 3:92

Thought about switching but seriously I only tow a utility trailer. It’s more of a complex I have personally.


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[ShamrockShooter]

Yeah I think on my test drive with the 3.21 I averaged about 12 mpg. But I opened it up a few times too. My Silverado has 3.42 and I can get 22 mpg with the 5.3 v8. So the mpg is giving me a moment of pause before switching. I will say I didn't want to get back in my 16 Silverado after driving a loaded Ram.

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[FirstTimeRamDriver]

Yeah I think on my test drive with the 3.21 I averaged about 12 mpg. But I opened it up a few times too. My Silverado has 3.42 and I can get 22 mpg with the 5.3 v8. So the mpg is giving me a moment of pause before switching. I will say I didn't want to get back in my 16 Silverado after driving a loaded Ram.

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First 1000 miles or so is not an indication. Real world, in last 2 days I have driven about 800 miles, with 91 octane fuel (wait for others to chime in and say it doesn’t matter and it’s a complete waste of money) with 3.92 on highway I got about 20 average. City and highway together about 17.5. I have about 2k miles on the truck and I am not expecting anything better. For me it’s awesome since my previous suv game me 14 on highway

 

[alangsam]

Hi there. I am a Silverado owner looking at buying a new ram2019. I found just the one I want in a Laramie trim as a dealer demo. The only thing is it has the 3.92 elock rear axle. I drive mostly highway and my trailer is only 3500 lbs. MPG is a bigger priority for me.

Can you easily swap to 3.21 gears or am I better off just trying to find another truck?

Sorry if I posted this in the wrong spot.

Thanks

Sent from my Pixel 2 using Tapatalk

you will get better mileage all things being equal with 3.21 vs 3.92 - RPMS willl be lower in 8th gear at 60MPH. long trips will benefit most. won't see much change in the City.

 

[ShamrockShooter]

you will get better mileage all things being equal with 3.21 vs 3.92 - RPMS willl be lower in 8th gear at 60MPH. long trips will benefit most. won't see much change in the City.

That's my other thought too. The 3.21 would seem to be quieter at 70 mph if it's turning 300 rpms lower than the 3.92? As much as I like the one particular truck on the lot I just don't think I can talk myself into the 3.92 when 99% of the time I am just cruising down the highway with no load or trailer.

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[ShamrockShooter]

Has anyone driven a 3.21 and a 3.92 and noticed a big difference in the overall driving experience?

What would the rpms be at say 70 mph with the 3.21 vs the 3.92?

The cost of swapping the rear gear for mpg alone is probably a 60k to 70k miles payback period. So it doesn't really seem like a viable option.

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[Andoskyy]

At 70mph i'm at 2000 RPM with 3.92.

My brother has an older gen (2017) with 3.21 and he says he's at 1500

not sure if the 8 speed ratios changed at all for the 2019 model year, but that's significant and will certainly have an impact on MPG

 

[Billet1500 4x4]

Has anyone driven a 3.21 and a 3.92 and noticed a big difference in the overall driving experience?

What would the rpms be at say 70 mph with the 3.21 vs the 3.92?

The cost of swapping the rear gear for mpg alone is probably a 60k to 70k miles payback period. So it doesn't really seem like a viable option.

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About 350 rpm difference at 70 mph. Roughly 1580 versus 1930 this would be ideal situation perfectly locked up Torque converter without any slip. Based upon factory 32" diameter tire.

I traded out of a 2015 GMC Z71 crew cab with the 5.3 and 6 speed to Ram with a 5.7 crew cab 4x4 hemi no e torque with 3.21 gears and sadly the fuel economy on the ram is no where near the GMC. I do a lot of city driving and the 3.21 gear set is terrible for the city. Freeway I can generally get 22-27 MPG at 70 MPH depending on road surface/headwind... Right now I average about 13 MPG mixed 70/30 city/highway. 400 hp versus 355 hp means more fuel its just physics. Direct injection versus port injection loses another 15% or so in effeciency. The GMC also had 3.42 gears which helped in the city as well versus the 3.21. For me I should have get the lower gears for the city, The MPG hit you take from 3.92s on the freeway is less than the MPG hit you take from the 3.21 in the city. Takes way more fuel to get the truck moving from a stop than it does to maintain speed once you're moving; again it's all physics no way around it.

 

[SpeedyV]

Has anyone driven a 3.21 and a 3.92 and noticed a big difference in the overall driving experience?

What would the rpms be at say 70 mph with the 3.21 vs the 3.92?

The cost of swapping the rear gear for mpg alone is probably a 60k to 70k miles payback period. So it doesn't really seem like a viable option.

Per other threads on this subject, running highway speed in 8th with 3.92s is very close to running the same speed in 7th with 3.21s. The 8-speed really helps to minimize the efficiency drain of the shorter gears.

 

[Billet1500 4x4]

Has anyone driven a 3.21 and a 3.92 and noticed a big difference in the overall driving experience?

What would the rpms be at say 70 mph with the 3.21 vs the 3.92?

The cost of swapping the rear gear for mpg alone is probably a 60k to 70k miles payback period. So it doesn't really seem like a viable option.

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If you want to see what RPM's do in relation to gear swap and tire size changes I made a spread sheet specific to the Ram. PM me so I can send you a link since you cannot post XLS files on the forum

 

[SpeedyV]

If you want to see what RPM's do in relation to gear swap and tire size changes I made a spread sheet specific to the Ram. PM me so I can send you a link since you cannot post XLS files on the forum

Want to post a PDF of it?

 

[ShamrockShooter]

Thanks for all the input.

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[Billet1500 4x4]

Want to post a PDF of it?

It's a fully function spread sheet that allows you to enter values in any of the green boxes and it will perform the calcs for you. Here's a screen shot. In the screen shot you can see its set for 3.21 factory gear set with 32" tires as well as the values for a 33 inch tire and 3.92 gears. It bases everything off of the displayed speed in the instrument cluster.

 

[alangsam]

It's a fully function spread sheet that allows you to enter values in any of the green boxes and it will perform the calcs for you. Here's a screen shot. In the screen shot you can see its set for 3.21 factory gear set with 32" tires as well as the values for a 33 inch tire and 3.92 gears. It bases everything off of the displayed speed in the instrument cluster.

I don’t know how to use pm. Can you email me the spreadsheet?


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[2wd]

The cost of the swap is gonna eat any fuel savings I imagine, unless you're driving 12-20K highway a year. The 3.21 is likely only to return better MPG on highway. In mixed driving, both rear ends will end up in the sweet spot with the 8 speed.

 

[Jagtyson]

Has anyone driven a 3.21 and a 3.92 and noticed a big difference in the overall driving experience?

What would the rpms be at say 70 mph with the 3.21 vs the 3.92?

The cost of swapping the rear gear for mpg alone is probably a 60k to 70k miles payback period. So it doesn't really seem like a viable option.

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For anyone interested...when my ivory 2019 ram was bought back by the dealer due to paint issues I ordered a 3:21 without tow mirrors verses my defective paint 3:92 with tow mirrors.

Here are the rpm/mpg pictures at 55, 65, 76 mph. You can compare to your 3:92 rear ends and maybe post similar pictures.

 

[riccnick]

If you want to drive over 65mph, I think it's actually worth it to have the 3.92's, because the truck is working less hard to move the front end through the air. I have an eTorque 3.21 truck and anything over 65mph the mpg drops from 20ish to 17 instantly. If you want to do 80mph expect 15mpg.