3.21 vs 3.92

[Gearhead22]

I currently have a 2013 single cab with a hemi and 3.55 gears and anti spin diff. It tows ok. I was wondering what the best ratio is for towing with the newer 8 speed trans.

 

[crash68]

If you have 3.55 now and say it tows ok, you probably need to go 3.92 How much/what are you planning on towing?
There is a lot more to having the lower(3.92) gearing than just getting the load rolling, there is less stress on the transmission.

 

[Gearhead22]

Sorry I guess I should have been more specific. I will be towing a 21 foot boat on weekends and maybe once a year have to tow a tractor. Not sure on the weight. I plan on upgrading trucks somtime in the near future and plan on gettin a crew cab and four wheel drive and the long term goal is little lift and possibly some 35's. I wasn't sure if the 3.92 gears would be to low for the 8 speed or just how it compared to my current setup.

 

[crazykid1994]

I have 3.92 and DD my truck. It's good on every day traffic. At 60mph I'm still pulling 27mpg. Any faster it goes down but even at 75 I'm still getting 19mpg. Can't say mpg for towing but I'm looking at getting a pop up and the 3.92 is rated around 10k lbs over 8k with the 3.21 gears. I plan on lifting and 35s. That's honestly why I got the 3.92 anyways. I'm hoping that brings the mpg in the higher speeds back a little like if I had 3.21s


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[norville]

zero regrets on my 2011 with 3.92s....

 

[14hemiexpress]

From what I have gathered the 3.21 8speed is about the same towing as a 6spd 3.55. and if your playing on bigger tires go 3.92. I have 5spd 3.55 and when my rear axle was rebuilt I wanted to pay the upcharge for 3.92 and they were on back order for over a month so I still have 3.55s. the final over drive gear is basically identical between the 8spd and the 6 there's just more between the 2.

 

[69GWC]

I currently have a 2013 single cab with a hemi and 3.55 gears and anti spin diff. It tows ok. I was wondering what the best ratio is for towing with the newer 8 speed trans.

I bought a hemi 8sp with 3:21s and am very happy with how it puts the power down, it will flat move out for such a high gear.
But with that said if I had not bought a left over for cheap I would have bought one with 3:92s no question.

 

[norville]

My 2011 CC 1500 has the 3.92, I drove the 3.21 also and both had a ton of power unladen but I have zero regrets on getting the 3.92's, especially when I haul the 30' Travel Trailer..

 

[norville]

good post over here;



http://www.ramforum.com/f38/8_spd_3_21_vs_6_spd_3_92_a-98581/

 

[Ed loves guns]

I have 3.92 and DD my truck. It's good on every day traffic. At 60mph I'm still pulling 27mpg. Any faster it goes down but even at 75 I'm still getting 19mpg. Can't say mpg for towing but I'm looking at getting a pop up and the 3.92 is rated around 10k lbs over 8k with the 3.21 gears. I plan on lifting and 35s. That's honestly why I got the 3.92 anyways. I'm hoping that brings the mpg in the higher speeds back a little like if I had 3.21s


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Huh?

 

[69GWC]

No way your knocking down a true 27mpg. with a hemi and 3:92s

 

[Rzrman328]

I think 21 was the best I ever saw.

 

[sbarron]

Hell, I have 3.92, 5.7, and 6-speed and I'm happy when I crack 15 combined. Which is almost never.


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[crazykid1994]

No way your knocking down a true 27mpg. with a hemi and 3:92s

At 55-60 average the evic is maxed out. Which when I've calculated by hand my evic seems to be about 1.5 mpg off


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[TRCM]

I think 21 was the best I ever saw.

I've seen 22 hand calculated, but that was @ 55 mph on level ground.

27 is not possible.

 

[sbarron]

21 or 22 from a hemi is pretty stellar and certainly not sustainable for DD mileage. 27 is ecodiesel highway mileage territory.


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[crazykid1994]

Well as I dd and get 18 average hand calculated when the evic says 19.5 and most of my driving is through town at around 35-40 I can assume the evic is probably wrong and I have never done only highway driving to know the actual I'm only assuming based on the evic. I know on the interstate doing 75 I averaged 19 hand calculated truck was empty with a tonneau cover And the evic said 20.


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[sbarron]

Those numbers I believe. Where did 27mpg at 75mph come from.

An an aside, Scientifically proven dCt that a tonneau doesn't at all help with mileage. In fact it hurts.


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[crazykid1994]

I said 60 mpg I got 27 but that was on the evic. I've never heard that a tonneau was bad for mpg


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[jescal76]

My 2011 CC 1500 has the 3.92, I drove the 3.21 also and both had a ton of power unladen but I have zero regrets on getting the 3.92's, especially when I haul the 30' Travel Trailer..

Just a quick question if you don't mind. Do you have the hemi? If so how does your truck do going up mountain passes? I usually don't like pushing over 4500 rpms and im still doing around 60. I'm talking about a steep climb from o to 5500ft. im also pulling a 28 foot travel trailer.