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3.21 vs 3.55 mpg?

7874 Views 6 Replies 6 Participants Last post by  captmac
I am buying a 2015 RAM 1500 quad cab with a 3.6 liter v6 engine. What is the mileage difference between these axel sizes?
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I have the 3.21 rear in a regular cab 2wd and 3.6. I get incredible fuel economy at 60 mph...something in the range of 32 mpg on level ground with no wind.

As I go faster (freeway driving) it gets worse. By 70 mph it has dropped to about 26 mpg and at 75 it was about 24 mpg. I began to wonder...if I did a lot of freeway driving (I don't as I live in rural Wisconsin) would it be better to have 3.55 gears with the 3.6L? Perhaps that would get me into a better power curve where the truck would do better at 70mph. I don't know. I can tell you that so far my fuel economy has been stellar with the 3.21 gears, only bothering me above 60 mph.
 

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Can't tell you anything about the 3.21 but on the 3.55 I get around 30mpg on the highway if I keep it below 70mph, usually cruise around 65mph. Around town I get around 22mpg. Now this is a Canadian(Imperial) gallon so its a bit more than a us gallon.
Also my towing capacity on the 3.55 is around 7200 lbs vs 4100 lbs for the 3.21.
 

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Discussion Starter · #6 ·
Thanks for the info. Plan on ordering a truck tomorrow. 2016 1500 quad cab 4x4 6.4 bed v6 outdoorsman black forest green 3.55 LSD . quite a change from my 2003 2500 quad 5.7 slt white 4x4. I'm hoping to get 18 mpg city and at least 23 highway at 69 mph.Is this realistic. I loved the 2500 but 9 mpg city and around 13.5 - 14.5 hwy cost me a tun in fuel.
 

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I have the 3.55 and my son inlaw has the 3.21. Mine is a quad cab 4wd. I also have an ATC cap on mine. I agree with HEMI HFE on the mileage difference. The 8 speed does a pretty good job of taking up the difference. I average around 21 mpg overall. I am a professional Hunting and Fishing guide and when pulling my boat the mileage drops considerably but I dont have to pull it far as I live on the water. The 3.6L is a gem of a motor and has plenty of power for my 4000 lb boat. The engine is a bit weight sensitive so if your adding say over a 1000 lbs in the bed your going to see/feel a performance difference not so much that it seems to strain the motor, just doesnt have quite the pep and the mileage drops a bit..... pulling my baot I get about 14mpg. P.S. have not had a minutes trouble out of the the truck ...it is all and more than I expected and I'm a die hard FORD kinda guy. Have had two recalls ...the software on Uconnect and now something to do with the airbags. Good luck!
 
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