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Old 09-16-2015, 12:38 PM   #1
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5.9L verses 6.7L inquiry

5.9L verses 6.7L inquiry...which is the better engine???
I am looking to buy a Ram 3500 Dually...... The tow limits are close on each....There are just so many more of the 5.9L to choose from than the 6.7L.... Which is the better engine... I know the gear ratio has alot to do with the towing... however, it seems there are more of the 3.73:1 than there are the 4.10:1...... will i be ok with the 5.9L/3.73:1 as long as i am within or close to being within the limits.....

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Old 09-16-2015, 01:04 PM   #2
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There both good diesel engines, and both of those gear ratios are good towing gears. That being said , the 6.7 is a towing beast completely stock. No need to chip it or whatever for more power. Now the 5.9's are wonderful engines, but if your going to tow a big 5er your probably going to want more power. The 5.9 will do the job just fine, and will pull any hill, but the 6.7's don't need any mods.

The 5.9's are simpler to work on, and there's no limit to how much horsepower you can build one of these up.

Now I'm sure you'll get a lot of other opinions on this matter.

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Old 09-16-2015, 01:47 PM   #3
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The most likely reason you see more 5.9s is they have been around much longer. I have the 5.9 with 4:10 gears and if I had a choice I would go with the 3:73 unless you plan on doing a LOT of heavy mountain pulling. My friend has same truck as mine but with 3:73 and typically gets 2 plus more mpg. No major problems that I can see on either engine. I love mine and it did a great job pulling my fiver up a 13% grade recently.
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Old 09-16-2015, 08:08 PM   #4
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Buy a new 15 off the lot, there are great discounts out there be sure to get an Aisin trans. More power and lower starting gears get the load moving easily. They are towing machines.

The 5.9 is a great engine but has a 4 speed trans. 6 speeds makes a world of difference when towing!

Rear air ride is great also. 4:10's will get the most towing capacity. I am extremely happy with my 4:10's and Aisin/6.7 combo.

The oil contamination is not a big deal any longer with the 13 and newer 6.7's the oil change interval is up to 15K now and the oil actually stays clean for a long tome compared to my 11 HO 6.7.

Truck and RV combined 32,540#

15,040 sitting on the 6 truck tires. Can't come close to that with a 5.9 Dually.

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Old 09-18-2015, 06:33 PM   #5
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Love my 15 a towing machine and I came from 2007 Duramax
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Old 09-19-2015, 08:19 AM   #6
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Originally Posted by ddown View Post
Love my 15 a towing machine and I came from 2007 Duramax
Fill in your profile, helps with answering questions.
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Old 09-19-2015, 08:32 PM   #7
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My 6.7 is so quiet compared to the 5.9 I had. Many people while riding with me ask "Is this a diesel?". It also tows like a champ.
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Old 09-21-2015, 09:55 PM   #8
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The 5.9L is certainly dependable as its been around awhile. The 6.7L has been increasing in power each year since its debut in 2007. When I bought my 2007 I had the choice of a new 5.9L or the 6.7L. I opted for the 6.7L for 2 reasons. The 6.7L has a far better designed 6spd transmission while the 5.9L's tranny often is the weak link in the drive train. 2nd reason is the 6.7L's turbo includes a built in exhaust brake. Really makes towing down steep grades easy.

That said the 2007/8 6.7L had a ton of growing pains. The emissions system on them were very problematic with numerous TSB's to correct. My turbo was replaced 3 times, EGR and heater grid cleaned repeatedly, O2 sensors replaced etc. I firmly believe the problems were all figured out and resolved. All issues warranted. Last issue was 4 years ago at around 30,000 miles. I now have 95,000 miles and zero troubles since.
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Old 09-21-2015, 10:26 PM   #9
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5.9 versus 6.7

Originally Posted by Rickthescot View Post
My 6.7 is so quiet compared to the 5.9 I had. Many people while riding with me ask "Is this a diesel?". It also tows like a champ.
Referencing noise, I think my 6.7's have been a slight bit more noisy than my friends 2015 Ford, but I've been so happy with the towing ability and the trustworthiness of the 6.7's, that I have no reason to look elsewhere. My "Ford friend" had to move my 5'er about 40 miles last week (due to a broken leg on my part) with my Ram, and he commented that it felt like a smooth pulling and shifting rig. My wife and I both enjoy the low noise level from the 2010, the 2011 and the 2015 that we've had. Our reason for trading so often is that we couldn't seem to get the selection right. 3rd time was a charm with the new dually.

The mileage on the 5.9 would likely be several MPG better under normal driving conditions, unless your towing in wind. I think you would find, as I have, the 6.7 mileage doesn't vary too much, wind or not. Mechanically, we have had "zero" mechanical issues with the 3 trucks. The one we currently have is towing in the 30K lb. GCVW range. With the 6 speeds and Aisin tranny, it pulls like a champ with the 3.73 gears.
2015 Ram 3500 Cummins Aisin dually 3.73 gear 2015 Dynamax Trilogy 5th wheel 39FB
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Old 09-25-2015, 05:02 AM   #10
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I am alittle biased, but I choose a 5.9L for two reasons... first was cost... a new truck was not reasonable for me. Second was emissions... the early 6.7's prior to DPF scared me. Too many friends spending small fortunes either fixing or replacing those emission systems. Although the 6 speed auto and exhaust brake would sure be nice. All in I absolutely love my 5.9L.

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