What gears for Cummins with 37's?

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Stork

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Hello everyone...I am new to the forum and new to Dodge/Ram all together. Yup, you could be talking to the newest convert from GM. Next spring I am likely going to be ordering a new 2017 Ram Laramie 2500...Cummins of course! I will be installing a 6" lift and 37" tires shortly after bringing her home. What do you all think about what gearing I should order in the truck, knowing I am going with the 37's? Is the standard 3:42 going to be good? I want optimum fuel economy and power for the setup. Thanks in advance for your input.
 

Dmopar74

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I do believe your only option is the 3.42 from the factory
 

Ram444

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I'm running that exact setup and the 342's are fine. If I had the option I would have went with a 411. My truck does have a slight rub under flex conditions even with the 6" lift. I could easily remedy that situation with some minor trimming.
 

KarL45

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Hope to see you next spring as a new Ram owner. As for gearing, in my humble opinion, think I would attempt to order it with somewhere around a 3.73 gear. that's the standard gear that the gas 6.4 uses. From the sound of things,I don't think you will be towing or hauling heavy with your Ram. If you "do" plan on heavy hauling, over 12k, then maybe the 4.11 would serve you better. Anything above the 4.11 probably would have you running about mid engine rpm just cruising on the hi way at 80. As an example, at 80, with the 3.73 gear, rpm's are about 1800. With the 4.56 that I changed to, the rpms are 2300. While 2300 is idleing for the 6.4 gas, it is well into the mid rpm range for the diesel. Just my thoughts.
 

usaf2006

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3.42s are all that are available from the factory, if you were unaware. So any gear upgrade will be aftermarket.
 

Wandell

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I'm running the stock 3.73 gears on mine with 37's. It runs great with my tuner set on the "mild" tune which adds about 60hp. It will still fry the tires from a dead stop.
 
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Stork

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Turns out 3:42's are the only factory option. With my plan to run the 37's, do you think it would be a better option to go with the 3500 and the upgraded AISIN trans? What do you think about the tradeoff of the 5-link rear suspension in the 2500 for the added torque and towing capacity of the 3500? I will be hauling a medium sized camper 8,500lbs and a horse trailer 8,500lbs from time to time.
 

Wandell

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Are you planning on tuning or deleting the truck? I've read that most of the tuners are struggling with trans tuning for the Aisin. That's something to consider.
 

Ram444

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My truck has the Aisin and is deleted. It has the stock 3:42 rear end. I've got the BullyDog GT and EFI Live tune with 4 separate settings. It runs better than stock by far on the mildest setting. Level 4 runs substantially better but is not needed for normal driving. I haven't tried to do any 0-60 or 1/4 mile runs because I have no intentions of racing a $80k 8000# truck.
 

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brandonjansen

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As others have said, 3.42's are going to be your only option from the factory for a Cummins equipped SRW truck. So you're stuck with those on your order. When I lifted my truck and put 37's on still running the stock 3.73's I thought it was an absolute dog and hated how it drove. Not to mention it's much harder on the trans that way. I ended up swapping to 4.56's. Now that being said, if I had to do it over again I probably would have done 4.10's. The 4.56's are great for city driving and it's an absolute beast when towing. But on the highway unloaded I run out of what I consider "comfortable" RPM to be running at. At about 75 mph I'm turning 2000 rpm.

So at the end of the day I'd say 4.10's are probably the best option for you but that will partially depend on what you plan to do with the truck.
 

NWRQC

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As others have said, 3.42's are going to be your only option from the factory for a Cummins equipped SRW truck. So you're stuck with those on your order. When I lifted my truck and put 37's on still running the stock 3.73's I thought it was an absolute dog and hated how it drove. Not to mention it's much harder on the trans that way. I ended up swapping to 4.56's. Now that being said, if I had to do it over again I probably would have done 4.10's. The 4.56's are great for city driving and it's an absolute beast when towing. But on the highway unloaded I run out of what I consider "comfortable" RPM to be running at. At about 75 mph I'm turning 2000 rpm.

So at the end of the day I'd say 4.10's are probably the best option for you but that will partially depend on what you plan to do with the truck.

Good advice.
 
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